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EAAIDD DOI: 10.1352/1944-7558-120.3.193
Spatial-Sequential and Spatial-Simultaneous Working Memory in Individuals With Williams Syndrome Silvia Lanfranchi, Letizia De Mori, Irene C. Mammarella, Barbara Carretti, and Renzo Vianello
Abstract The aim of the present study was to compare visuospatial working memory performance in 18 individuals with Williams syndrome (WS) and 18 typically developing (TD) children matched for nonverbal mental age. Two aspects were considered: task presentation format (i.e., spatial-sequential or spatial-simultaneous), and level of attentional control (i.e., passive or active tasks). Our results showed that individuals with WS performed less well than TD children in passive spatial-simultaneous tasks, but not in passive spatial-sequential tasks. The former’s performance was also worse in both active tasks. These findings suggest an impairment in the spatial-simultaneous working memory of individuals with WS, together with a more generalized difficulty in tasks requiring information storage and concurrent processing, as seen in other etiologies of intellectual disability. Key Words: Williams syndrome; spatial working memory; intellectual disability
The present research was designed to analyze working memory (WM) in individuals with Williams syndrome (WS) by studying how task presentation format and attentional control influenced their performance in visuospatial WM tasks in comparison with typically developing (TD) children matched for nonverbal mental age. From a theoretical standpoint, distinguishing among different WM subcomponents may shed light on the profile of various etiologies of intellectual disability (ID), and on that of individuals with WS in the present case. Interest in WM has continued to grow in the last 40 years because it is involved in various cognitive processes fundamental to several everyday-life activities. Baddeley and Hitch (1974) initially described WM as a limited capacity system in which the central executive component interacts with two subsidiary subcomponents used for the temporary storage of different classes of information, the speech-based phonological loop and the visuospatial sketchpad (see also Baddeley & Logie, 1999). In their model, the phonological loop is responsible for the temporary storage of verbal information. The items it contains are short-lived and mainS. Lanfranchi et al.
tained via a process of articulation. The visuospatial sketchpad stores visuospatial information, again only briefly, and it plays a key part in the generation and manipulation of mental images. Both storage systems depend on the central executive, an attentionally limited control system. On the other hand, according to the continuity model proposed by Cornoldi and Vecchi (2003) WM tasks can be distinguished in terms of two dimensions: a vertical and a horizontal continuum. In the vertical continuum, depending on the level of attentional control required, tasks can be divided into passive memory tasks, or simple storage tasks (based on the rote rehearsal of items strictly related to the nature of the stimuli to retain); and active memory tasks, or complex span tasks (requiring both the retention and a concurrent processing of the information). The horizontal continuum differentiates instead between different task presentation formats (e.g., verbal vs. visuospatial; visual vs. spatial-sequential vs. spatial-simultaneous). Analyzing cases of atypical development has contributed considerably to our understanding of how WM functions. Researchers have generally 193
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shown that children with various etiologies of ID perform less well than TD children in several WM tests, but their weaknesses are not always the same. It has been demonstrated, for instance, that individuals with Down syndrome usually have a specific deficit in passive verbal and spatialsimultaneous tasks, but not in spatial-sequential ones (e.g., Carretti, Lanfranchi, & Mammarella, 2013; Lanfranchi, Cornoldi, & Vianello, 2004), whereas people with WS are particularly impaired in passive visuospatial tasks, but not in verbal ones (e.g., Jarrold, Baddeley, & Hewes, 1999). The specificity of WM deficits in passive tasks disappears, however, when memory tasks involve attentional resources, that is in tasks requiring a high attentional control (i.e., active tasks). In fact, individuals with ID have been found to perform poorly in both verbal and visuo-spatial tasks demanding a high attentional control. This picture emerged from analyses on groups of individuals with non-specific ID (Carretti, Belacchi, & Cornoldi, 2010; Lanfranchi, Cornoldi, & Vianello, 2002), Down syndrome (Lanfranchi et al., 2004; Lanfranchi, Jerman, Dal Pont, Alberti, & Vianello, 2010; Lanfranchi, Jerman, & Vianello, 2009), and Fragile X syndrome (Lanfranchi, Cornoldi, Drigo, & Vianello, 2009), who performed less well than TD children of the same mental age in active WM tasks. Taken together, these results suggest that for individuals with ID, the presentation format of a passive task may be crucial in distinguishing between different cognitive profiles, whereas a greater involvement of active control should make these differences disappear. More generally, given that ID is related to a poor performance in tasks requiring a high attentional control, these data suggest that the controlled components of working memory are crucial to, and closely linked with how intelligence functions (see Engle, Tuholski, Laughlin, & Conway, 1999; Miyake, Friedman, Rettinger, Shah, & Hegarty, 2001, for a discussion).
Working Memory in Williams Syndrome WS is a developmental disorder caused by a hemizygous deletion of approximately 26 genes on the long arm of chromosome 7 (7q11.23; Peoples et al., 2000). It has an estimated prevalence in the range of 1 in 7,500 to 1 in 20,000 live births (Stromme, Bjornstad, & Ramstad, 2002). Most individuals with WS have ID between the upper and the middle range of the 194
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spectrum (Howlin, Davies, & Udwin, 1998; Udwin, Yule, & Martin, 1987). The cognitive profile of this syndrome is characterized by an unusual pattern of relative strengths and weaknesses in cognitive tasks, where deficits in visuospatial cognition and visuospatial construction (Martens, Wilson, & Reutens, 2008) coincide with strengths in some aspects of verbal abilities (Howlin et al., 1998; Udwin et al., 1987). As concerns WM, previous studies have suggested that individuals with WS have a relatively well-preserved verbal WM and a relatively impaired visuospatial WM, in both passive (e.g., Jarrold Baddeley, Hewes, 1999; Klein & Mervis, 1999; Wang & Bellugi, 1994) and active tasks (Carney, Brown, & Henry, 2013; Menghini, Addona, Costanzo, & Vicari, 2010; Rhodes et al. 2010). For example, Menghini et al. (2010) showed that individuals with WS performed less well than TD children in a forward spatial span task, and even worse in the backward version of the task. Several studies used the Corsi blocks task (e.g., Orsini et al., 1987), which only assesses the spatial component of the visuospatial sketchpad. In the Corsi blocks task, nine cubes are placed at random on a board and the examiner taps some of the cubes, in increasingly long sequences, and participants are asked to reproduce each sequence, either in forward or backward order. The distinction between visual and spatial WM was taken into account in more recent studies on visuospatial working memory in WS, but with rather inconsistent results. Some studies suggested that individuals with WS have a more severe spatial than visual WM impairment (e.g., Vicari, Bellucci, & Carlesimo, 2006), whereas others found a significant impairment in both visual and spatial WM (e.g., Rhodes et al., 2010; Sampaio, Sousa, Fernandez, Henriques, & Goncalves, 2008), and others even found no differences in either visual or spatial WM performance between WS and TD children matched for nonverbal mental age (Jarrold, Phillips, & Baddeley, 2007), although visual WM was worse than spatial WM in both groups. These diverse results of the previously mentioned studies may be due to participants’ chronological age or developmental level, and/or to the choice of control group. Such inconsistent findings could also stem from different tasks being used. It is worth noting, in fact, that the visual tasks used in most of the previously mentioned studies share some of the features of the spatial-simultaneous tasks Spatial Memory in Williams Syndrome
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proposed in the Cornoldi and Vecchi model of WM (see discussion that follows). In the present study, we focused on spatial WM. The description of visuospatial WM originally provided by Baddeley and Hitch (1974) has since been better defined, enabling a distinction between visual and spatial components first, and then between different processes associated with the spatial component (see e.g., Lecerf & de Ribaupierre 2005; Logie, 1995). According to Pazzaglia and Cornoldi (1999), and Cornoldi and Vecchi (2003), spatial WM can be separated into two components involved in memorizing patterns of spatial locations: (i) a simultaneous component needed to recall items that are presented at the same time; and (ii) a sequential component involved in recalling items presented one after the other. Several studies have demonstrated the feasibility and utility of this distinction in TD children (Mammarella et al., 2006), older adults (Mammarella, Borella, Pastore, & Pazzaglia, 2013), and individuals with Down syndrome (Carretti, et al., 2013; Lanfranchi, Carretti, et al., 2009). We aimed to analyze spatial WM performance in a group of individuals with WS using two presentation formats: (a) spatial-sequential (when items of information to be recalled were presented one after the other), and (b) spatialsimultaneous (when items of information to be recalled were presented simultaneously). We also manipulated how attentional control was involved by using (a) passive tasks (when information only had to be retained) and (b) active tasks (when information had to be retained and processed; Cornoldi & Vecchi, 2003). We chose to distinguish between performance in passive and active, and spatial-sequential and spatialsimultaneous tasks in order to shed more light on the spatial WM impairment in individuals with WS already described in the literature (e.g., Jarrold et al., 1999). As demonstrated in other etiologies of ID (e.g., Lanfranchi et al., 2004 in Down syndrome; Lanfranchi, Cornoldi, et al., 2009 in Fragile X syndrome), as well as in WS (Carney et al., 2013; Menghini et al., 2010; Rhodes et al. 2010), we expected individuals with WS to perform less well than TD controls of the same mental age in active tasks (requiring storage while performing a concurrent task) whatever the presentation format (spatial-sequential or spatialsimultaneous). Our literature review suggested that the impaired performance of individuals with ID in active tasks is probably due to their weaker S. Lanfranchi et al.
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attentional resources, which make it difficult for them to remember and manipulate information. We also planned to explore whether both the presentation formats considered (spatial-sequential and spatial simultaneous) are impaired in WS. Presumably, if individuals with WS have generalized visuospatial WM impairments, then TD controls could be expected to perform better in all the spatial tasks. But if individuals with WS have specific, spatial-simultaneous or spatialsequential WM impairments, then any differences would depend on the task presentation format used. In light of previous studies, we expected to find individuals with WS faring worse in passive spatial-simultaneous tasks than TD children of the same mental age, because these tasks demand the ability to integrate information in order to form a global representation–a skill that individuals with WS have difficulty acquiring (e.g., Bihrle, Bellugi, Delis, & Marks, 1989; Farran, 2005; Hoffman, Landau, & Pagani, 2003).
Method Participants The experimental group consisted of 18 children and adolescents (10 M, 8 F) with WS, between 7 and 19 years of age (M 5 13.5, SD 5 3.10), and with a mean mental age (MA) of 5.6 years (SD 5 11 months). They were all attending general education primary, secondary, or professional schools, and they all lived at home with their families. These participants were contacted through the Italian Association for People with WS, and through one of the authors’ personal contacts. The project was presented individually to families, and parents decided whether or not to participate on a voluntary basis. The diagnosis of WS was confirmed by parents/caregivers prior to testing, based on information received from appropriate health professionals in accordance with accepted criteria (see e.g., Morris, 2013). The control group consisted of 18 TD children (10 M, 8 F) between 4.7 and 6.4 years of age (M 5 5.7, SD 5 6 months), with a mean mental age of 5.5 years (SD 5 7 months). These children were enrolled at a preschool and a primary school. Participants in the WS and TD groups were individually matched for nonverbal mental age (to within 6 3 months) using the Logical Operations Test (Vianello & Marin, 1997). All participants in both groups were of Caucasian ethnicity and came from all over 195
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Italy. Italian was the first language of all study participants.
Materials and Procedures A test of general cognitive abilities, the Logical Operations Test (Vianello & Marin, 1997), was administered to match the two groups of participants. Four spatial working memory tasks (two spatial-sequential and two spatial-simultaneous) were also administered. General cognitive abilities. The Logical Operations test (Vianello & Marin, 1997) is an intelligence test that measures mental age in terms of the development of logical thinking. This test is inspired by the Piagetian theory of operational thinking and includes 18 tasks assessing the following areas of logical thinking: seriation, numeration, and classification. The Logical Operations test is less influenced by cultural and verbal components than the Wechsler Intelligence Scale (Wechsler, 1974; the correlation between the two test methods is .68), because it involves practical tasks that require virtually no verbal response. By comparison with other tests assessing nonverbal intelligence (such as Colored Raven’s Progressive Matrices, [Raven, Raven, & Court, 1992] or the Columbia Mental Maturity Scale, [Burgemeister, Blum, & Lorge]), it also involves the use of more concrete materials (real objects instead of printed matter), making it particularly appropriate for use with children who have ID. The split-half reliability is .87 (for a review, see Vianello & Marin, 1997). The children with WS and TD in our sample were matched on this measure of nonverbal intelligence, as suggested in Kover and Atwood (2013). Working memory tasks. Four working memory tasks were administered (i.e., one passive and one active spatial-sequential, and one passive and one active spatial-simultaneous), adapted from Lanfranchi et al. (2004), and already used with children with Down syndrome (Lanfranchi, Carretti, et al., 2009). A self-terminating procedure was used for all the tasks. For each task, participants were presented with a series of increasingly complex pairs of trials and the task continued as long as they were able to solve at least one of the two trials for a given level of difficulty. The procedure was stopped when participants were unable to solve either of the two trials on a given level. For each of the four tasks, the participants first completed some practice trials at the lowest 196
EAAIDD DOI: 10.1352/1944-7558-120.3.193
level of difficulty, and the task was only administered when the child appeared to have understood what the task entailed. The Cronbach alpha reliabilities of all the raw score measures of WM were computed for the whole sample. All the alpha coefficients were within an acceptable range for basic research (e.g., Nunnally & Bernstein, 1994), being .68 for the passive spatial-simultaneous task, .73 for the passive spatial-sequential task, .80 for the active spatial-simultaneous task, and .84 for the active spatial-sequential task. Spatial-sequential tasks. Passive spatial-sequential task. Participants were shown a path taken by a small frog on a 3 3 3 or 4 3 4 chessboard, and immediately after they had seen it, they were asked to retrace the path by moving the frog from cell to cell. There were four levels of difficulty depending on the number of steps along the frog’s path and the dimensions of the chessboard (3 3 3 for the first level with the frog taking two steps, and 4 3 4 for the other levels of difficulty, with the frog taking two, three, and then four steps). The frog’s steps were presented at a rate of approximately one step every 2 s. A score of 1 was given for every path recalled correctly. The final score was the sum of the scores for each trial (min. score 5 0; max score 5 8). This task is quite similar to the Corsi span task used in previous studies. The only difference lies in that the blocks are randomly positioned on the board in the Corsi task, whereas in the present task the locations are presented in series in a two-dimensional matrix. Active spatial-sequential task. Participants were asked to remember the frog’s starting point along a path on a 4 3 4 chessboard (where one of the 16 cells was colored red) and also to tap on the table whenever the frog jumped onto the red square. The frog jumped onto the red square once in every trial. The position from where it jumped onto the red square varied across trials. The task included four levels of difficulty, depending on the number of steps along the path (from two to five). A score of 1 was given for every trial completed correctly (when a participant remembered the path’s starting point and also tapped the table at the right moment). In all other cases, a score of 0 was awarded. The final score was the sum of the scores for each trial (min. score 5 0; max score 5 8). Spatial-simultaneous tasks. Passive spatial-simultaneous task. Participants were given 10 s to look at the positions of some green Spatial Memory in Williams Syndrome
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squares on a 2 3 2, 3 3 3, or 4 3 4 chessboard. Immediately after the board was withdrawn, they were asked to remember the locations of the green squares and point to their positions on a blank chessboard. The task involved four levels of difficulty, depending on the number of squares to remember (from two to three) and the size of the board, 2 3 2 on the first level, 3 3 3 on the second and third levels (with two and three green squares, respectively), and 4 3 4 on the fourth level (with three green squares). There were two trials for each level of difficulty. A score of 1 was given for every pattern of positions recalled correctly. The final score was the sum of the scores obtained (min score 5 0; max score 5 8). Active spatial-simultaneous task. Participants were given 10 s to look at the positions of some red squares on a 2 3 2, 3 3 3, or 4 3 4 chessboard. Sometimes the chessboard also contained a blue square, in which case participants had to tap on the table with their hand. Then they were asked to point to the positions of the red squares on an empty chessboard. The task included four levels of difficulty, depending on the number of squares to recall (from two to three) and the size of the board, which was 2 3 2 on the first level, 3 3 3 on the second and third levels (which contained two and three red squares, respectively), and 4 3 4 on the fourth level (with three red squares). There were two trials for each level of difficulty. A score of 1 was awarded when the child performed both the recall and the concurrent task correctly. In every other case, they scored 0. The final score was the sum of the scores obtained in the trials (min score 5 0; max score 5 8). Procedure. All testing was done in a quiet, well-lit room. Participants completed the Logical Operations test during a first session and the raw score obtained by each individual with WS in this test was used to match them with a child in the control group. Participants then completed the four visuospatial WM tasks, which were administered individually during two sessions with an interval of approximately 1 week between them, each session lasting approximately 20 min. The task presentation order was counterbalanced across participants using a Latin square design.
Results General Cognitive Abilities Table 1 shows the mean scores for the two groups in the Logical Operations test and the results of S. Lanfranchi et al.
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between-group comparisons in the matching variables. No significant differences emerged in the Logical Operations test, F(1, 34) 5 .004, p 5 .95; g2p 5 .001. For a solid group matching, Mervis and Klein-Tasman (2004) recommend considering only p levels higher than .5 to ensure that group distributions on the matching variable (Logical Operations raw score) overlap strongly. In our case, the p value for the match on the Logical Operations test was .95, suggesting a good group matching on nonverbal cognitive ability. According to Kover and Atwood (2013), a higher p value may reflect a lower power rather than a lack of effect, so Cohen’s d and variance ratios were computed to ensure a solid equivalence between the groups. Cohen’s d was .02 on the matching variable (the Logical Operations raw score), whereas the variance ratio was .96. Kover and Atwood suggest that groups can be considered adequately matched when Cohen’s d is close to 0 and the variance ratio is as close as possible to 1. Both criteria were met in our sample.
Working Memory Tasks The two groups’ mean scores in the WM tasks are shown in Figure 1. Given the small number of participants involved, we opted to run two 2 (group: WS vs. TD) 3 2 (attentional control: passive vs. active) ANOVA for the spatial-sequential and spatialsimultaneous tasks. Before conducting these analyses, the assumptions of normality were assessed using the Kolmogorov-Smirnov test and all the p values were . .10. For the spatial-sequential task, we found a significant effect of group, F(1,34) 5 6.02 , p , .05 g2p 5 .15, individuals with WS performing less well (M 5 3.69, SE 5 .44) than TD children (M 5 5.22, SE 5 .44). There was also a significant group 3 attentional control interaction, F(1,34) 5 15.79, p , .001 g2p 5 .32. Subsequent post hoc comparisons with Bonferroni’s correction showed that the group with WS (M 5 4.06, SE 5 .44) performed as well as the TD children (M 5 4.22, SE 5 .44) in the passive task, whereas the performance of individuals with WS (M 5 3.33, SE 5 .56) was worse than that of the TD children (M 5 6.22, SE 5 .56; p , .001) in the active task. For the spatial-simultaneous task, we found a significant effect of group, F(1,34) 5 4.10, p 5 .05 g2p 5 .11, individuals with WS performing less well (M 5 2.97, SE 5 .49) than TD children (M 5 197
EAAIDD DOI: 10.1352/1944-7558-120.3.193
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Table 1 Participants’ Characteristics Williams syndrome
LO
Raw score Mental age
Typical development
M
SD
Range
M
SD
Range
F
**p
8.06 5.5
2.49 0.11
3–12 4.4–6.4
8.11 5.5
2.54 0.11
3–12 4.4–6.4
.02 .04
.95 .85
Note. LO 5 Logical Operations task. **p , .01.
4.36, SE 5 .49) in both passive and active spatialsimultaneous tasks. The main effect of attentional control, and the interaction between group and attentional control were not significant.
Discussion and Conclusion The aim of the present study was to investigate spatial WM in individuals with WS. In particular, we focused on two dimensions: (a) the need for attentional control involved in the task and (b) the presentation format of the information to be recalled. Our analysis followed the model proposed by Cornoldi and Vecchi (2003), which distinguishes between two continuous dimensions, one related to the need for attentional control (i.e., passive tasks simply requiring the recall of the information presented, and active tasks requiring further processing before its recall), and the other to the presentation format of the tasks (e.g., verbal, visual, spatial, etc.). With this model in mind, we focused on spatial WM, adapting spatial tasks drawn from the literature (e.g., Lanfranchi, Carretti, et al., 2009; Lanfranchi, Baddeley, Gathercole, & Vianello, 2012) to investi-
Figure 1. Mean scores for the two groups in the working memory tasks. TD = Typically developing; WS = Williams syndrome. 198
gate how both the presentation format (spatialsimultaneous or spatial-sequential) and the attentional control demands (low or high) affected the performance of individuals with WS. These tasks were administered to a group of individuals with WS matched for nonverbal mental age with a group of TD children. The issue of how to match individuals with WS with TD children is complicated because the cognitive profile of the former is characterized by stronger verbal than visuospatial abilities (e.g., Dykens, Hodapp, & Finucane, 2000). Because the focus of our study was on the performance of individuals with WS in visuospatial WM tasks that involved virtually no verbal abilities, we matched the two groups on nonverbal reasoning. This enabled us to rule out the possibility of any differences in the spatial working memory tasks being related to a general weakness in nonverbal cognitive abilities. Judging from our results, individuals with WS perform less well than TD children in passive spatial-simultaneous tasks, but not in passive spatialsequential tasks. This finding suggests that in performing passive tasks, only the spatial-simultaneous component is impaired in WS, whereas the spatialsequential component is relatively well preserved. In agreement with previous studies (Bihrle et al., 1989; Farran, 2005; Hoffman et al., 2003), this confirms that individuals with WS are unable to combine information into a global representation, even when performing passive tasks. Earlier visuospatial research on individuals with WS, in which participants were asked to copy hierarchical stimuli and combine global and local features, had shown that they have difficulty in processing the global aspects of visuospatial stimuli (Bihrle et al., 1989). Farran (2005) also found that, although individuals with WS were able to process visual stimuli on both local and global levels, their performance was impaired when they were asked to group stimuli by shape, orientation, or spatial features (proximity). Hoffman et al. (2003) suggested that the global processing Spatial Memory in Williams Syndrome
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deficit of individuals with WS (see Farran, 2005) might reflect difficulties in planning and/or executing motor responses, rather than in their visuospatial perception. Our finding that individuals with WS performed less well in a passive spatial-simultaneous WM task confirmed that they are unable to create a global configuration of the information they receive, even when only a passive recall is required. Similar findings were reported by Lanfranchi, Carretti, et al. (2009), Carretti and Lanfranchi (2010), and Carretti et al. (2013) in individuals with Down syndrome, who revealed a specific impairment in spatial-simultaneous tasks, but not in spatial-sequential tasks. To explain these results, Lanfranchi, Carretti, et al. (2009) suggested that the spatial-simultaneous WM deficit seen in individuals with Down syndrome might be due to the need to process more than one item at a time. However, subsequent studies demonstrated that this weakness in spatial-simultaneous tasks persisted even when spatial locations were grouped to form a pattern (see Carretti et al., 2013), suggesting a role for encoding strategies. In the light of these findings, it would be interesting to explore whether the spatial-simultaneous deficit in individuals with WS persists when they are presented with locations grouped into meaningful patterns to induce them to use encoding strategies, as in Carretti et al. (2013). Another crucial issue in research on ID regards the influence of the degree of attentional control demanded by a task, because a greater attentional control is commonly associated with a worse performance. In the present study, individuals with WS performed worse than TD children in active tasks (both spatial-simultaneous and spatial-sequential), confirming previous findings in individuals with other intellectual disabilities (e.g,. Carretti et al., 2010; Carretti et al., 2013; Lanfranchi et al., 2004; Lanfranchi, Carretti, et al., 2009; Lanfranchi et al., 2010). When WM tasks involved both storing and processing information, individuals with WS performed less well than TD children regardless of the task presentation format. This result confirms the welldocumented importance of attentional control as a defining factor common to various types of ID (see, for example, Menghini et al., 2010). Further research should expand on our findings, analyzing verbal and visual WM presentation formats too. The findings of the present study have some theoretical and clinical implications. First, as suggested by the Cornoldi and Vecchi (2003) S. Lanfranchi et al.
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model, passive tasks can be very useful in distinguishing between different cognitive profiles of ID (In our setting, individuals with WS failed in the passive spatial-simultaneous task, but not in the passive spatial-sequential task.). On the other hand, when a greater attentional control is needed, individuals with different etiologies of ID including WS, Down syndrome (Lanfranchi et al., 2004), Fragile X syndrome (Lanfranchi, Cornoldi, et al., 2009), and other unspecified ID (Carretti et al., 2010), perform less well than TD children of the same mental age. Future research should therefore further analyze this aspect exploring other etiologies of ID. This would help clinicians and educators to plan specific intervention programs for different types of disorder, focusing on their patients’ strengths and weaknesses. For instance, they need to bear in mind that individuals with WS have problems with spatial WM when information is presented simultaneously, whereas their performance is consistent with their mental age when it is presented sequentially. That is why it would be appropriate to use separate and distinct information presentation formats in activities involving spatial WM. In summary, the present findings support the importance of distinguishing between different components of spatial WM, as explained by Pazzaglia and Cornoldi (1999), and demonstrated in typically developing individuals of various ages (e.g. Mammarella, Pazzaglia, & Cornoldi, 2008; Mammarella, et al., 2013), and with different ID profiles (e.g., in Down syndrome, as shown by Carretti et al., 2013). We found that individuals with WS performed just as well as TD children of the same mental age in passive spatial-sequential tasks, but not in passive spatial-simultaneous tasks, giving the impression that they process spatial-sequential and spatial-simultaneous stimuli differently. When we distinguished between active and passive tasks, on the other hand, individuals with WS revealed more problems in completing tasks that demand a high attentional control.
References Baddeley, A. D., & Hitch, G. J. (1974). Working memory. In G. H. Bower (Ed.), The psychology of learning and motivation (pp. 47–89). New York, NY: Academic Press. 199
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Baddeley, A. D., & Logie, R. H. (1999). Working memory: The multiple component model. I. In A. Miyake & P. Shah (Eds.), Models of working memory: Mechanisms of active maintenance and executive control (pp. 28–61). New York, NY: Cambridge University Press. Bihrle, A. M., Bellugi, U., Delis, D. C., & Marks, S. (1989). Seeing either the forest or the trees: Dissociation in visuospatial processing. Brain and Cognition, 11, 37–49. Burgemeister, B. B., Blum, L. H., & Lorge, I. (1972). Columbia Mental Maturity Scale: Guide for administering and interpreting. New York, NY: Harcourt Brace Jovanovich. Carney, D. P. J., Brown, J. H., & Henry, L. A. (2013). Executive function in Williams and Down syndromes. Research in Developmental Disabilities, 34, 46–55. doi: 10.1016/j.ridd. 2012.07.013 Carretti, B., Belacchi, C., & Cornoldi, C. (2010). Difficulties in working memory updating in individuals with intellectual disability. Journal of Intellectual Disability Research, 54(4), 337– 345. doi: 10.1111/j.1365-2788.2010.01267.x Carretti, B., & Lanfranchi, S. (2010). The effect of configuration on VSWM performance of Down syndrome individuals. Journal of Intellectual Disability Research, 54(12), 1058–1066. doi: 10.1111/j.1365-2788.2010.01334.x Carretti, B., Lanfranchi, S., & Mammarella, I. C. (2013). Spatial-simultaneous and spatial-sequential working memory in individuals with Down syndrome: The effect of configuration. Research in Developmental Disabilities, 34, 669– 675. doi: 10.1016/j.ridd.2012.09.011 Cornoldi, C., & Vecchi, T. (2003). Visuo-spatial working memory and individual differences. Hove, UK: Psychological Press. Dykens, E. M., Hodapp, R. M., & Finucane, B. (2000). Genetics and mental retardation syndromes: A new look at behavior and intervention. Baltimore, MD: Paul H. Brookes. Engle, R. M., Tuholski, S. W., Laughlin, J. E., & Conway, A. R. A. (1999). Working memory, short-term memory and general fluid intelligence: A latent variable approach. Journal of Experimental Psychology: General, 128, 309–331. Farran, E. K. (2005). Perceptual grouping ability in Williams syndrome: Evidence for deviant patterns of performance. Neuropsychologia, 43, 815–822. doi: 10.1016/j.neuropsychologia. 2004.09.001 200
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Henry, L. (2012). The development of working memory in children. London, UK: Sage. Hoffman, J. E., Landau, B., & Pagani, B. (2003). Spatial breakdown in spatial construction: Evidence from eye fixations in children with Williams syndrome. Cognitive Psychology, 46, 260–301. doi: 10.1016/S0010-0285(02) 00518-2 Howlin, P., Davies, M., & Udwin, O. (1998). Cognitive functioning in adults with Williams syndrome. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 39, 183–189. Jarrold, C., Baddeley, A. D., & Hewes, A. K. (1999). Genetically dissociated components of working memory: Evidence from Down’s and Williams syndrome. Neuropsychologia, 37, 637– 651. doi: 10.1016/S0028–3932(98)00128–6 Jarrold, C., Phillips, C., & Baddeley, A. D. (2007). Binding of visual and spatial short-term memory in Williams syndrome and moderate learning disability. Developmental Medicine and Child Neurology, 49, 270–273. doi: 10.1111/ j.1469-8749.2007.00270.x Klein, B. P., & Mervis, C. B. (1999). Contrasting patterns of cognitive abilities of 9- and 10year-olds with Williams syndrome or Down syndrome. Developmental Neuropsychology, 16, 177–196. Kover, S. T., & Atwood, A. K. (2013). Establishing equivalence: Methodological progress in group-matching design and analysis. American Journal on Intellectual and Developmental Disabilities, 118, 3–15. doi: 10.1352/1944-7558118.1.3 Lanfranchi, S., Baddeley, A., Gathercole, S., & Vianello, R. (2012). Working memory in Down syndrome: Is there a dual task deficit? Journal of Intellectual Disability Research, 56, 157–166. doi: 10.1111/j.1365-2788.2011.01444.x Lanfranchi, S., Carretti, B., Spano`, G., & Cornoldi, C. (2009). A specific deficit in visuospatialsimultaneous working memory in Down syndrome. Journal of Intellectual Disability Research, 53, 474–483. doi: 10.1111/j.1365-2788. 2009.01165.x Lanfranchi, S., Cornoldi, C., Drigo, S., & Vianello, R. (2009). Working memory in individuals with fragile X syndrome. Child Neuropsychology: A Journal on Normal and Abnormal Development in Childhood and Adolescence, 15, 105–119. doi: 10.1080/09297040802112564 Spatial Memory in Williams Syndrome
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Lanfranchi, S., Cornoldi, C., & Vianello, R. (2002). Working memory deficits in individuals with and without mental retardation. Journal of Cognitive Education and Psychology, 2, 301–312. Lanfranchi, S., Cornoldi, C., & Vianello, R. (2004). Verbal and visuospatial working memory deficits in children with Down syndrome. American Journal of Mental Retardation, 109, 456–466. doi:10.1352/0895-8017(2004)109 ,456:VAVWMD. 2.0.CO;2 Lanfranchi, S., Jerman, O., Dal Pont, E., Alberti, A., & Vianello, R. (2010). Executive function in adolescents with Down syndrome. Journal of Intellectual Disability Research, 54(4), 308– 319. doi: 10.1111/j.1365-2788.2010.01262.x Lanfranchi S., Jerman, O., & Vianello, R. (2009). Working memory, verbal abilities, visuospatial abilities and logical thinking in individuals with Down syndrome. Child Neuropsychology, 15, 397–416. doi: 10.1080/ 09297040902740652 Lecerf, T., & de Ribaupierre, A. (2005). Recognition in a visuospatial memory task: The effect of presentation. European Journal of Cognitive Psychology, 17, 47–75. doi: 10.1080/095414 40340000420 Logie, R. H. (1995). Visuo spatial working memory. Hove, UK: Lawrence Erlbaum. Mammarella, I. C., Borella, E., Pastore, M., & Pazzaglia, F. (2013). The structure of visuospatial memory in adulthood. Learning and Individual Differences, 25, 99–110. doi: 10. 1016/j.lindif.2013.01.014 Mammarella, I. C., Cornoldi, C., Pazzaglia, F., Toso, C., Grimoldi, M., & Vio, C. (2006). Evidence for a double dissociation between spatial-simultaneous and spatial-sequential working memory in visuospatial (nonverbal) learning disabled children. Brain and Cognition, 62, 58–67. doi: 10.1016/j.bandc.2006. 03.007 Mammarella, I. C., Pazzaglia, F. & Cornoldi, C. (2008). Evidence for different components in children’s visuospatial working memory. British Journal of Developmental Psychology, 26(3), 337–355. doi: 10.1348/026151007X236061 Martens, M. A., Wilson, S. J., & Reutens, D. C. (2008). Research review. Williams syndrome: A critical review of the cognitive, behavioral, and neuroanatomical phenotype. Journal of Child Psychology and Psychiatry, and Allied S. Lanfranchi et al.
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Disciplines, 49, 576–608. doi: 10.1111/j.14697610.2008.01887.x Menghini, D., Addona, F., Costanzo, F., & Vicari, S. (2010). Executive functions in individuals with Williams syndrome. Journal of Intellectual Disability Research, 54, 418–432. doi: 10.1111/ j.1365-2788.2010.01287.x Mervis, C. B., & Klein-Tasman, B. P. (2004). Methodological issues in group-matching designs: a levels for control variable comparisons and measurement characteristics of control and target variables. Journal of Autism and Developmental Disorders, 34, 7–17. doi: 0162-3257/04/0200-0007/0 Miyake, A., Friedman, N. P., Rettinger, D. A., Shah P. & Hegarty M. (2001). How are visuospatial working memory, executive functioning, and spatial abilities related? A latent variable analysis. Journal of Experimental Psychology: General 130, 621–640. doi: 00004785200112000-00003 Morris, C. A. (2013). Williams syndrome. In R. A. Pagon, M. P. Adam, T. D. Bird, C. R. Dolan, C. T. Fong, & K. Stephens (Eds.), GeneReviews [Internet]. Seattle, WA: University of Washington, Seattle. Nunnally, J. C., & Bernstein, I. H. (1994). Psychometric theory (3rd ed.). New York, NY: McGraw-Hill. Orsini, A., Grossi, D., Capitani, E., Laiacona, M., Papagno, C., & Vallar, G. (1987). Verbal and spatial immediate memory span: normative data from 1355 adults and 1112 children. Italian Journal of Neurological Science, 539–548. Pazzaglia, F., & Cornoldi, C. (1999). The role of distinct components of visuo-spatial working memory in the processing of texts. Memory (Hove, England), 7, 19–41. doi: 10.1080/ 741943715 Peoples, R., Franke, Y., Wang, Y. K., Perez-Jurado, L., Paperna, T., Cisco, M., & Francke, U. (2000). A physical map, including a BAC/ PAC clone contig, of the Williams-Beuren syndrome–deletion region at 7q11.23. American Journal of Human Genetics, 66, 47–68. doi: 10.1086/302722 Raven, J., Raven, J. C., & Court, J. H. (1998). Coloured progressive matrices. Oxford, UK: Oxford Psychologists Press. Rhodes, S. M., Riby, D. M., Park, J., Fraser, E., & Campbell, L. E. (2010). Executive neuropsychological functioning in individuals with Williams syndrome. Neuropsychologia, 48, 1216– 201
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1226. doi: 10.1016/j.neuropsychologia.2009. 12.021 Sampaio, A., Sousa, N., Fernandez, M., Henriques, M., & Goncalves, O. F. (2008). Memory abilities in Williams syndrome: Dissociation or developmental delay hypothesis? Brain and Cognition, 66, 290–297. doi: 10.1016/j.bandc. 2007.09.005 Stromme, P., Bjornstad, P. G., & Ramstad, K. (2002). Prevalence estimation of Williams syndrome. Journal of Child Neurology, 17, 269–271. doi: 10.1177/088307380201700406 Udwin, O., Yule, W., & Martin, N. (1987). Cognitive abilities and behavioural characteristics of children with idiopathic infantile hypercalcaemia. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 28, 297–309. Vianello, R., & Marin, M. L. (1997). OLC: Operazioni logiche e conservazione [LOC: Logical Operation and Conservation]. Bergamo, Italy: Junior. Vicari, S., Bellucci, S., & Carlesimo, G. A. (2006). Evidence from two genetic syndromes for the independence of spatial and visual working memory. Developmental Medicine and Child Neurology, 48, 126–131. doi: 10.1017/S00 12162206000272 Wang, P. P., & Bellugi, U. (1994). Evidence from two genetic syndromes for a dissociation between verbal and visual-spatial short-term
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memory. Journal of Clinical and Experimental Neuropsychology, 16, 317–322. doi: 10.1080/ 01688639408402641 Wechsler, D. (1974). Manual for the Wechsler Intelligence Scale for Children—Revised. New York, NY: Psychological Corporation. Received 4/30/2013, accepted 8/1/2014. We thank all children who took part in the study and their families.
Authors: Silvia Lanfranchi, Letizia De Mori, and Irene C. Mammarella, Department of Developmental Psychology and Socialization, University of Padova, Italy; Barbara Carretti, Department of General Psychology, University of Padova, Italy; and Renzo Vianello, Department of Developmental Psychology and Socialization, University of Padova, Italy. Correspondence concerning this article should be addressed to Silvia Lanfranchi, University of Padova, Dipartimento di Psicologia dello Sviluppo e della Socializzazione, Via Venezia 8, 35128 Padova, Italy (e-mail: [email protected]).
Spatial Memory in Williams Syndrome
EAAIDD DOI: 10.1352/1944-7558-120.3.193
Spatial-Sequential and Spatial-Simultaneous Working Memory in Individuals With Williams Syndrome Silvia Lanfranchi, Letizia De Mori, Irene C. Mammarella, Barbara Carretti, and Renzo Vianello
Abstract The aim of the present study was to compare visuospatial working memory performance in 18 individuals with Williams syndrome (WS) and 18 typically developing (TD) children matched for nonverbal mental age. Two aspects were considered: task presentation format (i.e., spatial-sequential or spatial-simultaneous), and level of attentional control (i.e., passive or active tasks). Our results showed that individuals with WS performed less well than TD children in passive spatial-simultaneous tasks, but not in passive spatial-sequential tasks. The former’s performance was also worse in both active tasks. These findings suggest an impairment in the spatial-simultaneous working memory of individuals with WS, together with a more generalized difficulty in tasks requiring information storage and concurrent processing, as seen in other etiologies of intellectual disability. Key Words: Williams syndrome; spatial working memory; intellectual disability
The present research was designed to analyze working memory (WM) in individuals with Williams syndrome (WS) by studying how task presentation format and attentional control influenced their performance in visuospatial WM tasks in comparison with typically developing (TD) children matched for nonverbal mental age. From a theoretical standpoint, distinguishing among different WM subcomponents may shed light on the profile of various etiologies of intellectual disability (ID), and on that of individuals with WS in the present case. Interest in WM has continued to grow in the last 40 years because it is involved in various cognitive processes fundamental to several everyday-life activities. Baddeley and Hitch (1974) initially described WM as a limited capacity system in which the central executive component interacts with two subsidiary subcomponents used for the temporary storage of different classes of information, the speech-based phonological loop and the visuospatial sketchpad (see also Baddeley & Logie, 1999). In their model, the phonological loop is responsible for the temporary storage of verbal information. The items it contains are short-lived and mainS. Lanfranchi et al.
tained via a process of articulation. The visuospatial sketchpad stores visuospatial information, again only briefly, and it plays a key part in the generation and manipulation of mental images. Both storage systems depend on the central executive, an attentionally limited control system. On the other hand, according to the continuity model proposed by Cornoldi and Vecchi (2003) WM tasks can be distinguished in terms of two dimensions: a vertical and a horizontal continuum. In the vertical continuum, depending on the level of attentional control required, tasks can be divided into passive memory tasks, or simple storage tasks (based on the rote rehearsal of items strictly related to the nature of the stimuli to retain); and active memory tasks, or complex span tasks (requiring both the retention and a concurrent processing of the information). The horizontal continuum differentiates instead between different task presentation formats (e.g., verbal vs. visuospatial; visual vs. spatial-sequential vs. spatial-simultaneous). Analyzing cases of atypical development has contributed considerably to our understanding of how WM functions. Researchers have generally 193
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shown that children with various etiologies of ID perform less well than TD children in several WM tests, but their weaknesses are not always the same. It has been demonstrated, for instance, that individuals with Down syndrome usually have a specific deficit in passive verbal and spatialsimultaneous tasks, but not in spatial-sequential ones (e.g., Carretti, Lanfranchi, & Mammarella, 2013; Lanfranchi, Cornoldi, & Vianello, 2004), whereas people with WS are particularly impaired in passive visuospatial tasks, but not in verbal ones (e.g., Jarrold, Baddeley, & Hewes, 1999). The specificity of WM deficits in passive tasks disappears, however, when memory tasks involve attentional resources, that is in tasks requiring a high attentional control (i.e., active tasks). In fact, individuals with ID have been found to perform poorly in both verbal and visuo-spatial tasks demanding a high attentional control. This picture emerged from analyses on groups of individuals with non-specific ID (Carretti, Belacchi, & Cornoldi, 2010; Lanfranchi, Cornoldi, & Vianello, 2002), Down syndrome (Lanfranchi et al., 2004; Lanfranchi, Jerman, Dal Pont, Alberti, & Vianello, 2010; Lanfranchi, Jerman, & Vianello, 2009), and Fragile X syndrome (Lanfranchi, Cornoldi, Drigo, & Vianello, 2009), who performed less well than TD children of the same mental age in active WM tasks. Taken together, these results suggest that for individuals with ID, the presentation format of a passive task may be crucial in distinguishing between different cognitive profiles, whereas a greater involvement of active control should make these differences disappear. More generally, given that ID is related to a poor performance in tasks requiring a high attentional control, these data suggest that the controlled components of working memory are crucial to, and closely linked with how intelligence functions (see Engle, Tuholski, Laughlin, & Conway, 1999; Miyake, Friedman, Rettinger, Shah, & Hegarty, 2001, for a discussion).
Working Memory in Williams Syndrome WS is a developmental disorder caused by a hemizygous deletion of approximately 26 genes on the long arm of chromosome 7 (7q11.23; Peoples et al., 2000). It has an estimated prevalence in the range of 1 in 7,500 to 1 in 20,000 live births (Stromme, Bjornstad, & Ramstad, 2002). Most individuals with WS have ID between the upper and the middle range of the 194
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spectrum (Howlin, Davies, & Udwin, 1998; Udwin, Yule, & Martin, 1987). The cognitive profile of this syndrome is characterized by an unusual pattern of relative strengths and weaknesses in cognitive tasks, where deficits in visuospatial cognition and visuospatial construction (Martens, Wilson, & Reutens, 2008) coincide with strengths in some aspects of verbal abilities (Howlin et al., 1998; Udwin et al., 1987). As concerns WM, previous studies have suggested that individuals with WS have a relatively well-preserved verbal WM and a relatively impaired visuospatial WM, in both passive (e.g., Jarrold Baddeley, Hewes, 1999; Klein & Mervis, 1999; Wang & Bellugi, 1994) and active tasks (Carney, Brown, & Henry, 2013; Menghini, Addona, Costanzo, & Vicari, 2010; Rhodes et al. 2010). For example, Menghini et al. (2010) showed that individuals with WS performed less well than TD children in a forward spatial span task, and even worse in the backward version of the task. Several studies used the Corsi blocks task (e.g., Orsini et al., 1987), which only assesses the spatial component of the visuospatial sketchpad. In the Corsi blocks task, nine cubes are placed at random on a board and the examiner taps some of the cubes, in increasingly long sequences, and participants are asked to reproduce each sequence, either in forward or backward order. The distinction between visual and spatial WM was taken into account in more recent studies on visuospatial working memory in WS, but with rather inconsistent results. Some studies suggested that individuals with WS have a more severe spatial than visual WM impairment (e.g., Vicari, Bellucci, & Carlesimo, 2006), whereas others found a significant impairment in both visual and spatial WM (e.g., Rhodes et al., 2010; Sampaio, Sousa, Fernandez, Henriques, & Goncalves, 2008), and others even found no differences in either visual or spatial WM performance between WS and TD children matched for nonverbal mental age (Jarrold, Phillips, & Baddeley, 2007), although visual WM was worse than spatial WM in both groups. These diverse results of the previously mentioned studies may be due to participants’ chronological age or developmental level, and/or to the choice of control group. Such inconsistent findings could also stem from different tasks being used. It is worth noting, in fact, that the visual tasks used in most of the previously mentioned studies share some of the features of the spatial-simultaneous tasks Spatial Memory in Williams Syndrome
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proposed in the Cornoldi and Vecchi model of WM (see discussion that follows). In the present study, we focused on spatial WM. The description of visuospatial WM originally provided by Baddeley and Hitch (1974) has since been better defined, enabling a distinction between visual and spatial components first, and then between different processes associated with the spatial component (see e.g., Lecerf & de Ribaupierre 2005; Logie, 1995). According to Pazzaglia and Cornoldi (1999), and Cornoldi and Vecchi (2003), spatial WM can be separated into two components involved in memorizing patterns of spatial locations: (i) a simultaneous component needed to recall items that are presented at the same time; and (ii) a sequential component involved in recalling items presented one after the other. Several studies have demonstrated the feasibility and utility of this distinction in TD children (Mammarella et al., 2006), older adults (Mammarella, Borella, Pastore, & Pazzaglia, 2013), and individuals with Down syndrome (Carretti, et al., 2013; Lanfranchi, Carretti, et al., 2009). We aimed to analyze spatial WM performance in a group of individuals with WS using two presentation formats: (a) spatial-sequential (when items of information to be recalled were presented one after the other), and (b) spatialsimultaneous (when items of information to be recalled were presented simultaneously). We also manipulated how attentional control was involved by using (a) passive tasks (when information only had to be retained) and (b) active tasks (when information had to be retained and processed; Cornoldi & Vecchi, 2003). We chose to distinguish between performance in passive and active, and spatial-sequential and spatialsimultaneous tasks in order to shed more light on the spatial WM impairment in individuals with WS already described in the literature (e.g., Jarrold et al., 1999). As demonstrated in other etiologies of ID (e.g., Lanfranchi et al., 2004 in Down syndrome; Lanfranchi, Cornoldi, et al., 2009 in Fragile X syndrome), as well as in WS (Carney et al., 2013; Menghini et al., 2010; Rhodes et al. 2010), we expected individuals with WS to perform less well than TD controls of the same mental age in active tasks (requiring storage while performing a concurrent task) whatever the presentation format (spatial-sequential or spatialsimultaneous). Our literature review suggested that the impaired performance of individuals with ID in active tasks is probably due to their weaker S. Lanfranchi et al.
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attentional resources, which make it difficult for them to remember and manipulate information. We also planned to explore whether both the presentation formats considered (spatial-sequential and spatial simultaneous) are impaired in WS. Presumably, if individuals with WS have generalized visuospatial WM impairments, then TD controls could be expected to perform better in all the spatial tasks. But if individuals with WS have specific, spatial-simultaneous or spatialsequential WM impairments, then any differences would depend on the task presentation format used. In light of previous studies, we expected to find individuals with WS faring worse in passive spatial-simultaneous tasks than TD children of the same mental age, because these tasks demand the ability to integrate information in order to form a global representation–a skill that individuals with WS have difficulty acquiring (e.g., Bihrle, Bellugi, Delis, & Marks, 1989; Farran, 2005; Hoffman, Landau, & Pagani, 2003).
Method Participants The experimental group consisted of 18 children and adolescents (10 M, 8 F) with WS, between 7 and 19 years of age (M 5 13.5, SD 5 3.10), and with a mean mental age (MA) of 5.6 years (SD 5 11 months). They were all attending general education primary, secondary, or professional schools, and they all lived at home with their families. These participants were contacted through the Italian Association for People with WS, and through one of the authors’ personal contacts. The project was presented individually to families, and parents decided whether or not to participate on a voluntary basis. The diagnosis of WS was confirmed by parents/caregivers prior to testing, based on information received from appropriate health professionals in accordance with accepted criteria (see e.g., Morris, 2013). The control group consisted of 18 TD children (10 M, 8 F) between 4.7 and 6.4 years of age (M 5 5.7, SD 5 6 months), with a mean mental age of 5.5 years (SD 5 7 months). These children were enrolled at a preschool and a primary school. Participants in the WS and TD groups were individually matched for nonverbal mental age (to within 6 3 months) using the Logical Operations Test (Vianello & Marin, 1997). All participants in both groups were of Caucasian ethnicity and came from all over 195
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Italy. Italian was the first language of all study participants.
Materials and Procedures A test of general cognitive abilities, the Logical Operations Test (Vianello & Marin, 1997), was administered to match the two groups of participants. Four spatial working memory tasks (two spatial-sequential and two spatial-simultaneous) were also administered. General cognitive abilities. The Logical Operations test (Vianello & Marin, 1997) is an intelligence test that measures mental age in terms of the development of logical thinking. This test is inspired by the Piagetian theory of operational thinking and includes 18 tasks assessing the following areas of logical thinking: seriation, numeration, and classification. The Logical Operations test is less influenced by cultural and verbal components than the Wechsler Intelligence Scale (Wechsler, 1974; the correlation between the two test methods is .68), because it involves practical tasks that require virtually no verbal response. By comparison with other tests assessing nonverbal intelligence (such as Colored Raven’s Progressive Matrices, [Raven, Raven, & Court, 1992] or the Columbia Mental Maturity Scale, [Burgemeister, Blum, & Lorge]), it also involves the use of more concrete materials (real objects instead of printed matter), making it particularly appropriate for use with children who have ID. The split-half reliability is .87 (for a review, see Vianello & Marin, 1997). The children with WS and TD in our sample were matched on this measure of nonverbal intelligence, as suggested in Kover and Atwood (2013). Working memory tasks. Four working memory tasks were administered (i.e., one passive and one active spatial-sequential, and one passive and one active spatial-simultaneous), adapted from Lanfranchi et al. (2004), and already used with children with Down syndrome (Lanfranchi, Carretti, et al., 2009). A self-terminating procedure was used for all the tasks. For each task, participants were presented with a series of increasingly complex pairs of trials and the task continued as long as they were able to solve at least one of the two trials for a given level of difficulty. The procedure was stopped when participants were unable to solve either of the two trials on a given level. For each of the four tasks, the participants first completed some practice trials at the lowest 196
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level of difficulty, and the task was only administered when the child appeared to have understood what the task entailed. The Cronbach alpha reliabilities of all the raw score measures of WM were computed for the whole sample. All the alpha coefficients were within an acceptable range for basic research (e.g., Nunnally & Bernstein, 1994), being .68 for the passive spatial-simultaneous task, .73 for the passive spatial-sequential task, .80 for the active spatial-simultaneous task, and .84 for the active spatial-sequential task. Spatial-sequential tasks. Passive spatial-sequential task. Participants were shown a path taken by a small frog on a 3 3 3 or 4 3 4 chessboard, and immediately after they had seen it, they were asked to retrace the path by moving the frog from cell to cell. There were four levels of difficulty depending on the number of steps along the frog’s path and the dimensions of the chessboard (3 3 3 for the first level with the frog taking two steps, and 4 3 4 for the other levels of difficulty, with the frog taking two, three, and then four steps). The frog’s steps were presented at a rate of approximately one step every 2 s. A score of 1 was given for every path recalled correctly. The final score was the sum of the scores for each trial (min. score 5 0; max score 5 8). This task is quite similar to the Corsi span task used in previous studies. The only difference lies in that the blocks are randomly positioned on the board in the Corsi task, whereas in the present task the locations are presented in series in a two-dimensional matrix. Active spatial-sequential task. Participants were asked to remember the frog’s starting point along a path on a 4 3 4 chessboard (where one of the 16 cells was colored red) and also to tap on the table whenever the frog jumped onto the red square. The frog jumped onto the red square once in every trial. The position from where it jumped onto the red square varied across trials. The task included four levels of difficulty, depending on the number of steps along the path (from two to five). A score of 1 was given for every trial completed correctly (when a participant remembered the path’s starting point and also tapped the table at the right moment). In all other cases, a score of 0 was awarded. The final score was the sum of the scores for each trial (min. score 5 0; max score 5 8). Spatial-simultaneous tasks. Passive spatial-simultaneous task. Participants were given 10 s to look at the positions of some green Spatial Memory in Williams Syndrome
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squares on a 2 3 2, 3 3 3, or 4 3 4 chessboard. Immediately after the board was withdrawn, they were asked to remember the locations of the green squares and point to their positions on a blank chessboard. The task involved four levels of difficulty, depending on the number of squares to remember (from two to three) and the size of the board, 2 3 2 on the first level, 3 3 3 on the second and third levels (with two and three green squares, respectively), and 4 3 4 on the fourth level (with three green squares). There were two trials for each level of difficulty. A score of 1 was given for every pattern of positions recalled correctly. The final score was the sum of the scores obtained (min score 5 0; max score 5 8). Active spatial-simultaneous task. Participants were given 10 s to look at the positions of some red squares on a 2 3 2, 3 3 3, or 4 3 4 chessboard. Sometimes the chessboard also contained a blue square, in which case participants had to tap on the table with their hand. Then they were asked to point to the positions of the red squares on an empty chessboard. The task included four levels of difficulty, depending on the number of squares to recall (from two to three) and the size of the board, which was 2 3 2 on the first level, 3 3 3 on the second and third levels (which contained two and three red squares, respectively), and 4 3 4 on the fourth level (with three red squares). There were two trials for each level of difficulty. A score of 1 was awarded when the child performed both the recall and the concurrent task correctly. In every other case, they scored 0. The final score was the sum of the scores obtained in the trials (min score 5 0; max score 5 8). Procedure. All testing was done in a quiet, well-lit room. Participants completed the Logical Operations test during a first session and the raw score obtained by each individual with WS in this test was used to match them with a child in the control group. Participants then completed the four visuospatial WM tasks, which were administered individually during two sessions with an interval of approximately 1 week between them, each session lasting approximately 20 min. The task presentation order was counterbalanced across participants using a Latin square design.
Results General Cognitive Abilities Table 1 shows the mean scores for the two groups in the Logical Operations test and the results of S. Lanfranchi et al.
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between-group comparisons in the matching variables. No significant differences emerged in the Logical Operations test, F(1, 34) 5 .004, p 5 .95; g2p 5 .001. For a solid group matching, Mervis and Klein-Tasman (2004) recommend considering only p levels higher than .5 to ensure that group distributions on the matching variable (Logical Operations raw score) overlap strongly. In our case, the p value for the match on the Logical Operations test was .95, suggesting a good group matching on nonverbal cognitive ability. According to Kover and Atwood (2013), a higher p value may reflect a lower power rather than a lack of effect, so Cohen’s d and variance ratios were computed to ensure a solid equivalence between the groups. Cohen’s d was .02 on the matching variable (the Logical Operations raw score), whereas the variance ratio was .96. Kover and Atwood suggest that groups can be considered adequately matched when Cohen’s d is close to 0 and the variance ratio is as close as possible to 1. Both criteria were met in our sample.
Working Memory Tasks The two groups’ mean scores in the WM tasks are shown in Figure 1. Given the small number of participants involved, we opted to run two 2 (group: WS vs. TD) 3 2 (attentional control: passive vs. active) ANOVA for the spatial-sequential and spatialsimultaneous tasks. Before conducting these analyses, the assumptions of normality were assessed using the Kolmogorov-Smirnov test and all the p values were . .10. For the spatial-sequential task, we found a significant effect of group, F(1,34) 5 6.02 , p , .05 g2p 5 .15, individuals with WS performing less well (M 5 3.69, SE 5 .44) than TD children (M 5 5.22, SE 5 .44). There was also a significant group 3 attentional control interaction, F(1,34) 5 15.79, p , .001 g2p 5 .32. Subsequent post hoc comparisons with Bonferroni’s correction showed that the group with WS (M 5 4.06, SE 5 .44) performed as well as the TD children (M 5 4.22, SE 5 .44) in the passive task, whereas the performance of individuals with WS (M 5 3.33, SE 5 .56) was worse than that of the TD children (M 5 6.22, SE 5 .56; p , .001) in the active task. For the spatial-simultaneous task, we found a significant effect of group, F(1,34) 5 4.10, p 5 .05 g2p 5 .11, individuals with WS performing less well (M 5 2.97, SE 5 .49) than TD children (M 5 197
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Table 1 Participants’ Characteristics Williams syndrome
LO
Raw score Mental age
Typical development
M
SD
Range
M
SD
Range
F
**p
8.06 5.5
2.49 0.11
3–12 4.4–6.4
8.11 5.5
2.54 0.11
3–12 4.4–6.4
.02 .04
.95 .85
Note. LO 5 Logical Operations task. **p , .01.
4.36, SE 5 .49) in both passive and active spatialsimultaneous tasks. The main effect of attentional control, and the interaction between group and attentional control were not significant.
Discussion and Conclusion The aim of the present study was to investigate spatial WM in individuals with WS. In particular, we focused on two dimensions: (a) the need for attentional control involved in the task and (b) the presentation format of the information to be recalled. Our analysis followed the model proposed by Cornoldi and Vecchi (2003), which distinguishes between two continuous dimensions, one related to the need for attentional control (i.e., passive tasks simply requiring the recall of the information presented, and active tasks requiring further processing before its recall), and the other to the presentation format of the tasks (e.g., verbal, visual, spatial, etc.). With this model in mind, we focused on spatial WM, adapting spatial tasks drawn from the literature (e.g., Lanfranchi, Carretti, et al., 2009; Lanfranchi, Baddeley, Gathercole, & Vianello, 2012) to investi-
Figure 1. Mean scores for the two groups in the working memory tasks. TD = Typically developing; WS = Williams syndrome. 198
gate how both the presentation format (spatialsimultaneous or spatial-sequential) and the attentional control demands (low or high) affected the performance of individuals with WS. These tasks were administered to a group of individuals with WS matched for nonverbal mental age with a group of TD children. The issue of how to match individuals with WS with TD children is complicated because the cognitive profile of the former is characterized by stronger verbal than visuospatial abilities (e.g., Dykens, Hodapp, & Finucane, 2000). Because the focus of our study was on the performance of individuals with WS in visuospatial WM tasks that involved virtually no verbal abilities, we matched the two groups on nonverbal reasoning. This enabled us to rule out the possibility of any differences in the spatial working memory tasks being related to a general weakness in nonverbal cognitive abilities. Judging from our results, individuals with WS perform less well than TD children in passive spatial-simultaneous tasks, but not in passive spatialsequential tasks. This finding suggests that in performing passive tasks, only the spatial-simultaneous component is impaired in WS, whereas the spatialsequential component is relatively well preserved. In agreement with previous studies (Bihrle et al., 1989; Farran, 2005; Hoffman et al., 2003), this confirms that individuals with WS are unable to combine information into a global representation, even when performing passive tasks. Earlier visuospatial research on individuals with WS, in which participants were asked to copy hierarchical stimuli and combine global and local features, had shown that they have difficulty in processing the global aspects of visuospatial stimuli (Bihrle et al., 1989). Farran (2005) also found that, although individuals with WS were able to process visual stimuli on both local and global levels, their performance was impaired when they were asked to group stimuli by shape, orientation, or spatial features (proximity). Hoffman et al. (2003) suggested that the global processing Spatial Memory in Williams Syndrome
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deficit of individuals with WS (see Farran, 2005) might reflect difficulties in planning and/or executing motor responses, rather than in their visuospatial perception. Our finding that individuals with WS performed less well in a passive spatial-simultaneous WM task confirmed that they are unable to create a global configuration of the information they receive, even when only a passive recall is required. Similar findings were reported by Lanfranchi, Carretti, et al. (2009), Carretti and Lanfranchi (2010), and Carretti et al. (2013) in individuals with Down syndrome, who revealed a specific impairment in spatial-simultaneous tasks, but not in spatial-sequential tasks. To explain these results, Lanfranchi, Carretti, et al. (2009) suggested that the spatial-simultaneous WM deficit seen in individuals with Down syndrome might be due to the need to process more than one item at a time. However, subsequent studies demonstrated that this weakness in spatial-simultaneous tasks persisted even when spatial locations were grouped to form a pattern (see Carretti et al., 2013), suggesting a role for encoding strategies. In the light of these findings, it would be interesting to explore whether the spatial-simultaneous deficit in individuals with WS persists when they are presented with locations grouped into meaningful patterns to induce them to use encoding strategies, as in Carretti et al. (2013). Another crucial issue in research on ID regards the influence of the degree of attentional control demanded by a task, because a greater attentional control is commonly associated with a worse performance. In the present study, individuals with WS performed worse than TD children in active tasks (both spatial-simultaneous and spatial-sequential), confirming previous findings in individuals with other intellectual disabilities (e.g,. Carretti et al., 2010; Carretti et al., 2013; Lanfranchi et al., 2004; Lanfranchi, Carretti, et al., 2009; Lanfranchi et al., 2010). When WM tasks involved both storing and processing information, individuals with WS performed less well than TD children regardless of the task presentation format. This result confirms the welldocumented importance of attentional control as a defining factor common to various types of ID (see, for example, Menghini et al., 2010). Further research should expand on our findings, analyzing verbal and visual WM presentation formats too. The findings of the present study have some theoretical and clinical implications. First, as suggested by the Cornoldi and Vecchi (2003) S. Lanfranchi et al.
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model, passive tasks can be very useful in distinguishing between different cognitive profiles of ID (In our setting, individuals with WS failed in the passive spatial-simultaneous task, but not in the passive spatial-sequential task.). On the other hand, when a greater attentional control is needed, individuals with different etiologies of ID including WS, Down syndrome (Lanfranchi et al., 2004), Fragile X syndrome (Lanfranchi, Cornoldi, et al., 2009), and other unspecified ID (Carretti et al., 2010), perform less well than TD children of the same mental age. Future research should therefore further analyze this aspect exploring other etiologies of ID. This would help clinicians and educators to plan specific intervention programs for different types of disorder, focusing on their patients’ strengths and weaknesses. For instance, they need to bear in mind that individuals with WS have problems with spatial WM when information is presented simultaneously, whereas their performance is consistent with their mental age when it is presented sequentially. That is why it would be appropriate to use separate and distinct information presentation formats in activities involving spatial WM. In summary, the present findings support the importance of distinguishing between different components of spatial WM, as explained by Pazzaglia and Cornoldi (1999), and demonstrated in typically developing individuals of various ages (e.g. Mammarella, Pazzaglia, & Cornoldi, 2008; Mammarella, et al., 2013), and with different ID profiles (e.g., in Down syndrome, as shown by Carretti et al., 2013). We found that individuals with WS performed just as well as TD children of the same mental age in passive spatial-sequential tasks, but not in passive spatial-simultaneous tasks, giving the impression that they process spatial-sequential and spatial-simultaneous stimuli differently. When we distinguished between active and passive tasks, on the other hand, individuals with WS revealed more problems in completing tasks that demand a high attentional control.
References Baddeley, A. D., & Hitch, G. J. (1974). Working memory. In G. H. Bower (Ed.), The psychology of learning and motivation (pp. 47–89). New York, NY: Academic Press. 199
AMERICAN JOURNAL ON INTELLECTUAL AND DEVELOPMENTAL DISABILITIES 2015, Vol. 120, No. 3, 193–202
Baddeley, A. D., & Logie, R. H. (1999). Working memory: The multiple component model. I. In A. Miyake & P. Shah (Eds.), Models of working memory: Mechanisms of active maintenance and executive control (pp. 28–61). New York, NY: Cambridge University Press. Bihrle, A. M., Bellugi, U., Delis, D. C., & Marks, S. (1989). Seeing either the forest or the trees: Dissociation in visuospatial processing. Brain and Cognition, 11, 37–49. Burgemeister, B. B., Blum, L. H., & Lorge, I. (1972). Columbia Mental Maturity Scale: Guide for administering and interpreting. New York, NY: Harcourt Brace Jovanovich. Carney, D. P. J., Brown, J. H., & Henry, L. A. (2013). Executive function in Williams and Down syndromes. Research in Developmental Disabilities, 34, 46–55. doi: 10.1016/j.ridd. 2012.07.013 Carretti, B., Belacchi, C., & Cornoldi, C. (2010). Difficulties in working memory updating in individuals with intellectual disability. Journal of Intellectual Disability Research, 54(4), 337– 345. doi: 10.1111/j.1365-2788.2010.01267.x Carretti, B., & Lanfranchi, S. (2010). The effect of configuration on VSWM performance of Down syndrome individuals. Journal of Intellectual Disability Research, 54(12), 1058–1066. doi: 10.1111/j.1365-2788.2010.01334.x Carretti, B., Lanfranchi, S., & Mammarella, I. C. (2013). Spatial-simultaneous and spatial-sequential working memory in individuals with Down syndrome: The effect of configuration. Research in Developmental Disabilities, 34, 669– 675. doi: 10.1016/j.ridd.2012.09.011 Cornoldi, C., & Vecchi, T. (2003). Visuo-spatial working memory and individual differences. Hove, UK: Psychological Press. Dykens, E. M., Hodapp, R. M., & Finucane, B. (2000). Genetics and mental retardation syndromes: A new look at behavior and intervention. Baltimore, MD: Paul H. Brookes. Engle, R. M., Tuholski, S. W., Laughlin, J. E., & Conway, A. R. A. (1999). Working memory, short-term memory and general fluid intelligence: A latent variable approach. Journal of Experimental Psychology: General, 128, 309–331. Farran, E. K. (2005). Perceptual grouping ability in Williams syndrome: Evidence for deviant patterns of performance. Neuropsychologia, 43, 815–822. doi: 10.1016/j.neuropsychologia. 2004.09.001 200
EAAIDD DOI: 10.1352/1944-7558-120.3.193
Henry, L. (2012). The development of working memory in children. London, UK: Sage. Hoffman, J. E., Landau, B., & Pagani, B. (2003). Spatial breakdown in spatial construction: Evidence from eye fixations in children with Williams syndrome. Cognitive Psychology, 46, 260–301. doi: 10.1016/S0010-0285(02) 00518-2 Howlin, P., Davies, M., & Udwin, O. (1998). Cognitive functioning in adults with Williams syndrome. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 39, 183–189. Jarrold, C., Baddeley, A. D., & Hewes, A. K. (1999). Genetically dissociated components of working memory: Evidence from Down’s and Williams syndrome. Neuropsychologia, 37, 637– 651. doi: 10.1016/S0028–3932(98)00128–6 Jarrold, C., Phillips, C., & Baddeley, A. D. (2007). Binding of visual and spatial short-term memory in Williams syndrome and moderate learning disability. Developmental Medicine and Child Neurology, 49, 270–273. doi: 10.1111/ j.1469-8749.2007.00270.x Klein, B. P., & Mervis, C. B. (1999). Contrasting patterns of cognitive abilities of 9- and 10year-olds with Williams syndrome or Down syndrome. Developmental Neuropsychology, 16, 177–196. Kover, S. T., & Atwood, A. K. (2013). Establishing equivalence: Methodological progress in group-matching design and analysis. American Journal on Intellectual and Developmental Disabilities, 118, 3–15. doi: 10.1352/1944-7558118.1.3 Lanfranchi, S., Baddeley, A., Gathercole, S., & Vianello, R. (2012). Working memory in Down syndrome: Is there a dual task deficit? Journal of Intellectual Disability Research, 56, 157–166. doi: 10.1111/j.1365-2788.2011.01444.x Lanfranchi, S., Carretti, B., Spano`, G., & Cornoldi, C. (2009). A specific deficit in visuospatialsimultaneous working memory in Down syndrome. Journal of Intellectual Disability Research, 53, 474–483. doi: 10.1111/j.1365-2788. 2009.01165.x Lanfranchi, S., Cornoldi, C., Drigo, S., & Vianello, R. (2009). Working memory in individuals with fragile X syndrome. Child Neuropsychology: A Journal on Normal and Abnormal Development in Childhood and Adolescence, 15, 105–119. doi: 10.1080/09297040802112564 Spatial Memory in Williams Syndrome
AMERICAN JOURNAL ON INTELLECTUAL AND DEVELOPMENTAL DISABILITIES 2015, Vol. 120, No. 3, 193–202
Lanfranchi, S., Cornoldi, C., & Vianello, R. (2002). Working memory deficits in individuals with and without mental retardation. Journal of Cognitive Education and Psychology, 2, 301–312. Lanfranchi, S., Cornoldi, C., & Vianello, R. (2004). Verbal and visuospatial working memory deficits in children with Down syndrome. American Journal of Mental Retardation, 109, 456–466. doi:10.1352/0895-8017(2004)109 ,456:VAVWMD. 2.0.CO;2 Lanfranchi, S., Jerman, O., Dal Pont, E., Alberti, A., & Vianello, R. (2010). Executive function in adolescents with Down syndrome. Journal of Intellectual Disability Research, 54(4), 308– 319. doi: 10.1111/j.1365-2788.2010.01262.x Lanfranchi S., Jerman, O., & Vianello, R. (2009). Working memory, verbal abilities, visuospatial abilities and logical thinking in individuals with Down syndrome. Child Neuropsychology, 15, 397–416. doi: 10.1080/ 09297040902740652 Lecerf, T., & de Ribaupierre, A. (2005). Recognition in a visuospatial memory task: The effect of presentation. European Journal of Cognitive Psychology, 17, 47–75. doi: 10.1080/095414 40340000420 Logie, R. H. (1995). Visuo spatial working memory. Hove, UK: Lawrence Erlbaum. Mammarella, I. C., Borella, E., Pastore, M., & Pazzaglia, F. (2013). The structure of visuospatial memory in adulthood. Learning and Individual Differences, 25, 99–110. doi: 10. 1016/j.lindif.2013.01.014 Mammarella, I. C., Cornoldi, C., Pazzaglia, F., Toso, C., Grimoldi, M., & Vio, C. (2006). Evidence for a double dissociation between spatial-simultaneous and spatial-sequential working memory in visuospatial (nonverbal) learning disabled children. Brain and Cognition, 62, 58–67. doi: 10.1016/j.bandc.2006. 03.007 Mammarella, I. C., Pazzaglia, F. & Cornoldi, C. (2008). Evidence for different components in children’s visuospatial working memory. British Journal of Developmental Psychology, 26(3), 337–355. doi: 10.1348/026151007X236061 Martens, M. A., Wilson, S. J., & Reutens, D. C. (2008). Research review. Williams syndrome: A critical review of the cognitive, behavioral, and neuroanatomical phenotype. Journal of Child Psychology and Psychiatry, and Allied S. Lanfranchi et al.
EAAIDD DOI: 10.1352/1944-7558-120.3.193
Disciplines, 49, 576–608. doi: 10.1111/j.14697610.2008.01887.x Menghini, D., Addona, F., Costanzo, F., & Vicari, S. (2010). Executive functions in individuals with Williams syndrome. Journal of Intellectual Disability Research, 54, 418–432. doi: 10.1111/ j.1365-2788.2010.01287.x Mervis, C. B., & Klein-Tasman, B. P. (2004). Methodological issues in group-matching designs: a levels for control variable comparisons and measurement characteristics of control and target variables. Journal of Autism and Developmental Disorders, 34, 7–17. doi: 0162-3257/04/0200-0007/0 Miyake, A., Friedman, N. P., Rettinger, D. A., Shah P. & Hegarty M. (2001). How are visuospatial working memory, executive functioning, and spatial abilities related? A latent variable analysis. Journal of Experimental Psychology: General 130, 621–640. doi: 00004785200112000-00003 Morris, C. A. (2013). Williams syndrome. In R. A. Pagon, M. P. Adam, T. D. Bird, C. R. Dolan, C. T. Fong, & K. Stephens (Eds.), GeneReviews [Internet]. Seattle, WA: University of Washington, Seattle. Nunnally, J. C., & Bernstein, I. H. (1994). Psychometric theory (3rd ed.). New York, NY: McGraw-Hill. Orsini, A., Grossi, D., Capitani, E., Laiacona, M., Papagno, C., & Vallar, G. (1987). Verbal and spatial immediate memory span: normative data from 1355 adults and 1112 children. Italian Journal of Neurological Science, 539–548. Pazzaglia, F., & Cornoldi, C. (1999). The role of distinct components of visuo-spatial working memory in the processing of texts. Memory (Hove, England), 7, 19–41. doi: 10.1080/ 741943715 Peoples, R., Franke, Y., Wang, Y. K., Perez-Jurado, L., Paperna, T., Cisco, M., & Francke, U. (2000). A physical map, including a BAC/ PAC clone contig, of the Williams-Beuren syndrome–deletion region at 7q11.23. American Journal of Human Genetics, 66, 47–68. doi: 10.1086/302722 Raven, J., Raven, J. C., & Court, J. H. (1998). Coloured progressive matrices. Oxford, UK: Oxford Psychologists Press. Rhodes, S. M., Riby, D. M., Park, J., Fraser, E., & Campbell, L. E. (2010). Executive neuropsychological functioning in individuals with Williams syndrome. Neuropsychologia, 48, 1216– 201
AMERICAN JOURNAL ON INTELLECTUAL AND DEVELOPMENTAL DISABILITIES 2015, Vol. 120, No. 3, 193–202
1226. doi: 10.1016/j.neuropsychologia.2009. 12.021 Sampaio, A., Sousa, N., Fernandez, M., Henriques, M., & Goncalves, O. F. (2008). Memory abilities in Williams syndrome: Dissociation or developmental delay hypothesis? Brain and Cognition, 66, 290–297. doi: 10.1016/j.bandc. 2007.09.005 Stromme, P., Bjornstad, P. G., & Ramstad, K. (2002). Prevalence estimation of Williams syndrome. Journal of Child Neurology, 17, 269–271. doi: 10.1177/088307380201700406 Udwin, O., Yule, W., & Martin, N. (1987). Cognitive abilities and behavioural characteristics of children with idiopathic infantile hypercalcaemia. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 28, 297–309. Vianello, R., & Marin, M. L. (1997). OLC: Operazioni logiche e conservazione [LOC: Logical Operation and Conservation]. Bergamo, Italy: Junior. Vicari, S., Bellucci, S., & Carlesimo, G. A. (2006). Evidence from two genetic syndromes for the independence of spatial and visual working memory. Developmental Medicine and Child Neurology, 48, 126–131. doi: 10.1017/S00 12162206000272 Wang, P. P., & Bellugi, U. (1994). Evidence from two genetic syndromes for a dissociation between verbal and visual-spatial short-term
202
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memory. Journal of Clinical and Experimental Neuropsychology, 16, 317–322. doi: 10.1080/ 01688639408402641 Wechsler, D. (1974). Manual for the Wechsler Intelligence Scale for Children—Revised. New York, NY: Psychological Corporation. Received 4/30/2013, accepted 8/1/2014. We thank all children who took part in the study and their families.
Authors: Silvia Lanfranchi, Letizia De Mori, and Irene C. Mammarella, Department of Developmental Psychology and Socialization, University of Padova, Italy; Barbara Carretti, Department of General Psychology, University of Padova, Italy; and Renzo Vianello, Department of Developmental Psychology and Socialization, University of Padova, Italy. Correspondence concerning this article should be addressed to Silvia Lanfranchi, University of Padova, Dipartimento di Psicologia dello Sviluppo e della Socializzazione, Via Venezia 8, 35128 Padova, Italy (e-mail: [email protected]).
Spatial Memory in Williams Syndrome
