Perceptual a n d Motor Skills, 1976,42, 543-553. @ Perceptual and Motor Skills 1976
ORIENTING RESPONSES AS A FUNCTION OF AGE AND TASK COMPLEXITY1 ROGER L. GREENE Texrrs Tech Universify Summary.-Age-related differences i n the elicitation and habituation of orienting responses to the onset and offset of stimuli have been suggested by several authors. Eleccrodermal and cardiac orienting responses to the onset and offset of a visual stimulus were measured i n three age groups ( 4 yr., 7 yr., and undergraduate). Each S made one of three judgments: non-signal (observe stimulus), content (co!or of stimulus), and duration (length of time stimulus presented). Few age differences were found in elicitation or habituation of orienting responses to stimulus onset o r offset. There was a trend for elicitation of orienting responses to stimulus offset to be age-related, but the failure to find any other age-related changes made this difference somewhat questionable. Instructions as to the judgment to be made by S were the primary determinants of orienting responses to stimulus onset and offset across all age groups.
Stern (1968) hypothesized that habituation of the "terminal OR [the orienting response to the offset of a stimulus] is intimately tied up with the organism's ability to bind or conceptualize time, while the onset OR is more concerned with the content of the material encompassed by time" (p. 408). In a test of this hypothesis Beideman and Stern (1971) asked college students to judge either the duration or content (pitch) of a tone. They reported that Ss who judged stimulus content produced more orienting responses t o stimulus onset than offset. Those Ss who judged stimulus duration produced as many orienting responses to stimulus onset as offset. The number of orienting responses to stimulus onset did not differ between the t w o groups but the group judging duration showed more orienting responses to stimulus offset than those judging content. They concluded that the orienting response to stimulus onset and offset may be related to "memory storage of the content and duration of a stimulus respectively" (Beideman & Stern, 1971, p. 380). However, Greene, Dengerink, and Staples (1974) in a replication and extension of this study found no direct relationship between orienting responses to stimulus onset and stimulus content, or between orienting responses to stimulus offset and stimulus duration as Stern had postulated. Rather it appeared that the orienting response could be elicited at any point during a stimulus merely by altering the type of instructions which Ss were given. Stern (1968) also reported a pilot study in which orienting responses to the offset of a 6-sec. non-signal tone, a tone to which S attends without making 'This research is based upon a dissertation submitted in partial fulfillment of the requitements for the Ph.D. at Washington State University. The author would like to thank the members of his committee. Garv G. Galbraith and Ronald H. H o ~ k i n s .and ~articularlv for reprints should-be sent to-the author his chairman, Harold A. ~ e n ~ e i i n kRequests . at the Department of Psychology, Texas Tech University, Lubbock, Texas 79409.
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any response, occurred with much greater frequency and regularity in 6- and 12-yr.-old children than in college students. Six-yr.-olds also gave more orienting responses to the offset of the tone and habituated more slowly than 12-yr.-olds. Scern hypothesized that the orienting response to scimulus offset may be a reflection of the organism's ability to conceptualize time and as such should be highly correlated with measures of attention; these increase as a function of age and experience. In other words, the better the organism is able to conceptualize time, the faster the orienting response to stimulus offset should habituate. He also mentioned (personal communication, 1973) that with a non-signal stimulus Ss may self-instruct themselves and these self-instructions may differ as a function of age. The exact nature of these self-instructions was not made explicit nor was why they should vary as a function of age. The question that remains unanswered at this point is how to explain the age-related differences in orienting responses to stimulus offset which Stern reported. Within a Sokolovian framework the rapidity with which a matchmismatch model of the stimulus is constructed should increase with the age and experience of the organism. Also, as the complexity of the stimulus decreases there should be an increase in the rapidity with which the model is constructed. Thus, habituation of orienting responses should reflect both the age and experience of the organism as well as the complexity of the stimulus. A somewhat similar notion to this latter point has been suggested by Walley and Weiden (1973) who stated that the degree of phasic increase in arousal varies directly with task complexity. The first step in understanding these age-related changes in orienting responses to stimulus onset and offset is a parametric investigation of the variables of age and task complexity. Three ages of Ss ( 4 yr., 7 yr., and undergraduate) and three levels of task complexity (non-signal, content, and duration) were combined factorially. All Ss were presented with a constant visual stimulus which varied in color and duration between trials. The three levels of task complexity involved judging the color or duration of the stimulus or merely watching the stimulus. Electrodermal and cardiac measures of orienting responses were used so that their relationship can be examined. Finally, a dishabituation trial was included to examine the specific aspects of the stimulus to which Ss had habituated. Although the judgments of stimulus content and duration are similar to those used by Beideman and Scern (1973), this experiment was not intended to be a test of Stern's hypothesis that orienting responses to stimulus onset and offset are related to stimulus content and stimulus duration. Greene, et al. ( 1974) found that there were more parsimonious interpretations of the patterns of orienting responses produced by task demands. Instead, these judgments were used as points along a dimension of task complexity, which also allowed for comparisops with these studies.
ORIENTING RESPONSE, AGE, COMPLEXIW
METHOD Sabjectr Forty-five males and 45 females in 3 age groups served as Ss. The first group included 15 male and 15 female college undergraduates enrolled in introductory psychology at Washington State University. Students in these classes volunteer for experiments to earn course credit. The second group of Ss were 15 boys and 15 girls, 7 and 8 yr. old. These children were recruited through friends and acquaintances of the experimenter. The third group of Ss were 15 boys and 15 girls, 4 yr. old. Nineteen of the 4-yr.-olds were obtained through the Washington State University Nursery School. The remainder were recruited through friends and acquaintances of the experimenter. Only 2 parents of the 69 who were contacted refused to allow their children to participate. Three 4-yr.-olds and one 7-yr.-old were replaced because they did not understand the instructions. Nine college students had to be replaced because their cardiac data were not scoreable due to equipment failure during the initial phases of the experiment. During the remainder of the experiment, one college student, one 7-yr.-old, and two 4-yr.-olds had to be replaced because of E's inability to obtain a scoreable cardiac response. All Ss, except che 19 4-yr.-olds tested at the University Nursery School, were tested in an Industrial Acoustics Company soundproof room. The 19 4yr.-olds were tested in an observation room at the Nursery School. During the experiment S sat 0.3 m in front of a 0.63- X 0.63-m wooden box which contained a 0.21- X 0.23-m rear projection screen. A response panel with two response buttons was mounted across the bottom of the wooden box. A light located directly below the rear projection screen indicated when S was to respond. S's responses on the buttons illuminated a panel in the adjoining room, where all the programming and recording apparatus were located. The stimuli were presented by a Kodak Carousel projector. The projector lamp (GE ELH) had a rise time of 270 msec. The slides were constructed from red, blue, and green theatrical gels, which appeared subjectively to be of equal intensity. A Tally tape reader programmed the stimuli and their duration, the response light, and the polygraph signal marker. Silver-silver chloride electrodes (Edelberg, 1967) and a Grass Model 79 polygraph with a 7P1 preamplifier were used to record electrodermal responses. A 7P4 preamplifier was used to record cardiac responses. Pro cedgre Upon arriving at the laboratory each S within his respective age group was randomly assigned to one of 3 conditions. Random assignment of Ss to conditions was constrained so that there was an equal number of male and female Ss within each condition. After S was seated within the soundproof room,
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the electrodermal electrodes were attached to the palm and back of the left hand. T h e cardiac electrodes were attached using standard lead configuration I1 ( Brener, 1967 ) . T h e stimulus series was identical for all 3 groups. T w o hues (red and green) of slides of 2 durations (8 or 16 sec.) were randomly assigned across the 16 trials. During Trial 1 7 a blue slide was presented for 4 sec. For all three groups a variable intertrial interval of 10, 15, or 20 sec. was used. T h e intertrial interval was measured from the onset of the light signaling S to respond to the onset of the next slide. O n the first 16 trials the light signaling S to report his judgment appeared 5 to 1 0 sec. following stimulus offset and remained on until S made a response. S was not required to make any judgment for Trial 17. E recorded S's judgrnencs from the panel onto the polygraph record. There were three experimental condicions within each age: non-signal, content, and duration. In the non-signal condition S was asked to sic quietly and watch the slides. T h e light signaling S co make his judgment was disconnected for this condition. In [he content condition S was asked co judge whether the slides were red or green. T h e light signaling S to make his judgment also illuminated small red and green slides directly above the two response buttons. In the duration condition S was asked to judge whether the slides were of short or long duration. T o enable the children to make this judgment, all Ss in the condition were instructed to count throughout the stimulus duration. Using this procedure S found an approximate number which corresponded to short and long. T h e college Ss were told that Trial 1 would be short and Trial 2 would be long. T h e children were assisced in counting for Trials 1 and 2 and also shown when to push the response button. N o further assistance in counting was given to any S. Some of the children had to be reminded to wait to push or to push the response button. N o assistance in which button to push was given after Trial 2. T h e response buctons were marked by cards.with symbols for short and long, which were taped over the slides on the response panel. For the two younger age groups a second E remained with S throughout the experiment. T h e children selected a small toy as a reward for their participation.
RESULTS Electrodermal Responses
T w o criteria were used to score electrodermal responses as orienting responses. Skin resistance respmses greater than 200 ohms from the prestimulus baseline which occurred between 0.5 and 3.0 sec. after stimulus onset or offset were considered responses. Skin resistance responses were converted to skin conductance responses by the Psychophysiological Data Preparation Program (Greene & Bertilson, 1 9 7 3 ) . This program also computed the frequency and
ORIENTING RESPONSE, AGE, COMPLEXITY
547
amplitude of skin conductance responses as well as the amplitude of skin conductance responses corrected for individual differences in range (Lykken, e t al., 1966). Each of these response measures was averaged into four blocks of four trials/block. Any trial on which S made an incorrect judgment was excluded from the data analysis. Using this criterion 2.8% of the total trials were excluded. T h e analysis of the frequency of skin conductance responses and the amplitude of skin conductance responses corrected for individual differences in range were virtually identical which seemed to preclude the necessity of reporting both measures. The fact that the frequency data were discontinuous, which violates the assumptions of analysis of v~riance,was recognized. However, a separate analysis of the amplitude of skin conductance responses corrected for individual differences in range, which involved continuous data, yielded identical results. Frequency of skin conductance responses will be reported to enhance comparability wich two earlier articles on orienting responses to stimulus offset (Beideman & Stern, 1973; Greene, e t al., 1 9 7 4 ) , which employed frequency measures. A more complete description of the results is presented in Greene (1974). T h e frequency of orienting responses co stimulus onset and offset across the 16 trials in four blocks were used in the data analysis. These data were subjected to an age by sex by condition by response by block analysis of variance. T h e mean frequency of orienting responses by block for each condition are presented in Table 1. The main effects for condition ( F z V s 1 = 18.96), response (1;1,81 = 18.29), and block = 17.08) were significant. The maln effect for age ( F 2 , s l = 2.65) was not reliable. T h e interaction of condition by response by block (Flj,234= 3.34) was significant. This interaction reflected the observation that orienting responses ro stimulus offset habituated in the content and duration conditions and either did not habituate in the non-signal condition or habituated extremely rapidly. In the latter condition orienting responses to stimulus offset were infrequent throughout all blocks. There was no difference in habituation of orienting responses to stimulus onset between the three conditions. All post hoc tests were made wich the Newman-Keuls test for comparison of cell means. Only one comparison of orienting responses to stimulus onset was significant. Orienting responses were more frequent in the content and duration conditions than in the non-signal condition during Block 3. Comparisons of orienting responses to scin~ulusoffset yielded the following significant differences. More responses were observed in the duration condition during Blocks 1 to 4 and in the content condition during Blocks 1 to 3 than in the non-signal condition. More responses were observed in the duration condition during Blocks 2 and 4 than in the content condition. Comparing responses across blocks within conditions, a number of significant differences were found. More orienting responses to stimulus onset were observed in the non-signal condition during Blocks 1 to 3 than to
548
R. L. GREENE TABLE 1 MEANFREQUENCY OF ORIENTING AND TERMINAL ORIENTING RESPONSES BY
Age
AGE,CONDITION, AND BLOCK
Block Non-signal
OR* 4 yr.
TOR
Condition Content
OR
TOR
2.70 1.10 3.20 2.70 2.60 1.40 2.40 2.70 1.40 1.80 3.10 2.20 1.80 1.30 1.70 1.90 1.40 2.38 2.13 2.60 7 yr. 2.80 1.20 3.20 2.50 2.30 1.80 0.90 2.80 2.70 0.90 3.10 3 1.50 4 1.40 1.30 2.30 1.80 Total 1.88 1.08 2.33 2.85 College 1 2.60 2.50 0.70 3.30 2 0.50 1.80 1.20 1.60 0.60 1.50 1.00 3 1.50 1.00 1.40 1.10 4 1.90 Total 1.90 0.70 2.30 1.45 'OR, Orienting response; TOR, Terminal orienting response. 1 2 3 4 Total 1 2
Duration OR TOR 2.50 1.60 2.10 2.40 2.15 3.10 2.50 2.20 2.60 2.60 3.10 2.30 2.60 1.60 2.40
2.80 2.90 2.50 2.30 2.63 2.90 3.20 2.80 2.90 2.95 3.40 2.70 2.20 2.20 2.63
stimulus offset. More orienting responses to stimulus onset were observed in the content condition during Blocks 1 and 3 than to scimulus offset. In the duration condition, however, more oriencing responses to stimulus offset were observed during Block 2. The data for the dishabicuacion trial were analyzed by comparing the frequency of skin conductance responses to Trials 16 and 17. These data were subjected to an age by sex by condition by response by trial analysis of variance. The main effects for condition ( F z , 8 1 = 6.62 ), response ( F l , s l = 11.77), and trial ( F l , s l =. 12.36) were significant. Again, the main effect for age ( F Z , ~ ~ = 0.71) was not significant. The interaction of condition by response (FI?,81= 5.67) and the interaction of condition by trial ( F l q s l = 3.20) were both significant, but the interaction of condition by response by trial ( F 2 , 8 1 = 1.95) was not. Mean frequencies of oriencing responses by age and condition for Trials 16 and 17 are presented in Table 2. More responses co stimulus onset than offset were observed in che content condition, while more responses to stimulus offset than onset were observed in che duration condition. Significancly more responses to stimulus offset were observed in the duration condition than in the non-signal condition. The interaction of condition by trial reflected that more responses were observed in the content and duration conditions on Trial 17 than on Trial 16. Significantly more responses were observed in the duration condition than
ORIENTING RESPONSE, AGE, COMPLEXITY TABLE 2 MEANFREQUENCY OF ORIENTING AND T M I N A LORlENTlNG RESPONSES BY AGE AND CONDITION FOR TR~ALS 16 AND 17 Age
4 yr. 7 yr.
College
Trial
16 17 16 17 16 17
Non-signal ORr TOR
Condition Content OR TOR
0.30 0.40 0.30 0.70 0.50 0.90
0.40 0.90 0.50 1.00 0.70 0.90
0.30 0.30 0.40 0.10 0.30 0.00
0.50 0.60 0.30 0.50 0.20 0.50
Duration OR TOR 0.50 0.70 0.70 0.70 0.30 0.50
0.60 0.50 0.80 0.80 0.40 0.70
'OR, Orienting response; TOR, Terminal orienting response. in the non-signal condition on Trial 16. Comparing trials within conditions, significantly more responses were observed in the content condition on Trial 17 than on Trial 16. Cmrdiac R esponser
Heart rate was recorded at 1-sec. intervals for a period of 5 sec. beginning at stimulus onset and offset. Heart-rate level at stimulus onset and offset was not significantly different between conditions or condition within ages. There were substantial differences, however, in mean tonic level heart rate in beats per minute between the three age groups: college (75.3), 7-yr.-old (83.2), and 4-yr.-old (100.6). The heart-rate data were analyzed as a change score expressed as a difference score from the pre-onset or pre-offset baseline. A separate analysis of the heart-rate change scores corrected for individual differences in range as well as an analysis of covariance yielded similar results and will not be described. The mean heart-rate change scores were subjected to an age by sex by condition by response by block by time analysis of variance. Only the main = 13.77) was significant. Neither the main effect for effect for time (F4,324 age nor condition was reliable. The interaction of age by condition by response by time ( F l f i , ~ = 4 2.46) was significant. To facilitate interpretation of this interaction, separate analyses were conducted within each condition, and significant effects were subjected to trend analysis (Wilson, 1974). In the non-signal condition there were no significant main effects or interaction terms. The small change in mean heart rate was similar to stimulus onset and offset in all three age groups. If cardiac orienting responses are defined as heart-rate deceleration (Graham & Clifton, 1966 ) , orienting responses were displayed by 7-yr.-olds and college students to stimulus onset and by 4-yr.-olds and college students to stimulus offset. These figures are not displayed since there were no significant effects.
5 50
C
W
=
R. L. GREENE
-2.00
-
COLLEGE FOUR SEVEN
SECONDS
FIG. 1.
Mean onset of heart-rate change
by age for content
-
-
COLLEGE FOUR SEVEN
SECONDS
FIG. 2. Mean offset of heart-rate change by age for content
In the content condition the age by response by time interaction ( F B . l o a= 2.45) was significant. The mean heart-rate change scores for this interaction = 4.32) and cubic trends are illustrated in Figs. 1 and 2. Both the linear (F:..'7 = 13.65) within the interaction of age by time were significant to stimulus onset. T h e same two trends were also reliable within the main effect of ; 14.35) and cubic trends ( F l q s 7 = 10.33) within cime. Only the linear ( F I n 2 = the main effect of time were significant to stimul~lsoffset. None of the trends within the age by block by time interaction was reliable either to stimulus onset or offset. Inspection of Fig. 1 and a separate contrast of college students with 7- and 4-yr.-olds showed that the cubic trend was more pronounced to stimulus onset in the college students. T w o other findings should be noted: first, habituation either did not occur or occurred very rapidly within the first few trials; and second, 4-yr.-olds did not display orienting responses to stimulus onset or offset, while 7-yr.-olds and college students displayed orienting responses to both. In the duration condition the interaction of age by response by time ( F s . l o s = 2.26) was also significant. Mean heart-rate change scores for this interaction are illustrated in Figs. 3 and 4. Trend analysis revealed that only the linear = 4.56) and cubic trends ( F 1 , 2 i = 6.11) within the main effect of time were significant to stimulus onset. Both the linear ( F , , 2 i = 6.07) and cubic trends ( F 2 , 2 i = 4.57) within the interaction of age by time were significant to stimulus offset. The cubic trend within the main effect of time was also significant to stimulus offset. Again, none of the trends within the age by block by cime interaction was reliable either to stimulus onset or offset. Four-yr.-olds again did not display orienting responses to stimulus onset or offset, while both
ORIENTING RESPONSE, AGE, COMPLEXITY
551
-COLLEGE c--r FOUR -SEVEN
SECONDS
SECONDS
FIG. 3. Mean onset of heart-rare change by age for duration
FIG. 4. Mean offset of heart-rate change by age for duration
7-yr.-olds and college students displayed orienting responses to stimulus onset, s and 7-yr.-olds displayed oriencing responses to s c i m u l ~ ~offset. T h e data for the dishabituation trial were analyzed by comparing mean heart-rate change scores to Trials 16 and 17. Since the stimulus for Trial 17 lasted only 4 sec., heart rate was only recorded for a period of 4 sec. following stimulus onset and offset. These data were subjected ro an age by sex by condition by response t y trial by time analysis of variance. None of the interactions of a p r i o ~ iinterest was significant. Only the interaction of trial by time (P3,24:1 = 2.74) and the interaction of condition by response by time (FD,2.1R = 2.48) were significant. There was no systematic pattern to the cardiac orienting responses elicited during Trials 16 and 17. orienting responses did occur less frequently in the 4-yr.-olds than in the two older age groups.
DISCUSSION Stern ( 1968) reported that electrodermal orienting responses to the offset of a non-signal tone were more frequent in 6- and 12-yr.-old children than in college students. H e also reported that habituation of orienting responses to stimulus offset was slower in children than in college students. The non-signal condition in the present experiment, however, did not replicate these age differences. In fact there were no significant age differences in elicitation of orienting responses to stimulus onset or offset with the electrodermal measure. Habituation of the electrodermal orienting response to stimulus offset either did nor occur or occurred very rapidly in all three groups. There were significant age differences in elicitation of orienting responses to stimulus onset and offset with the cardiac measure. T h e general pattern was one in which orienting responses
.
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were elicited to any stimulus change in the two older age groups, while 4-yr.-olds displayed defensive responses rather than orienting responses to stimulus change. That is, college students and 7-yr.-olds displayed cardiac orienting responses to stimulus onset and offset in all three conditions, while 4-yr.-olds displayed only defensive responses. Orienting response to stimulus offset, rather than being more frequent in younger children as Stern found with an electrodermal measure, did not occur in the 4-yr.-olds with a cardiac measure. Habituation of the cardiac orienting response either did not occur or occurred very rapidly in all three age groups in all conditions. The trend of the age differences within the non-signal condition with the electrodermal measure, however, was identical to that reported by Stern. Frequency of orienting responses to stimulus offset was ordered from 4-~r.-oldsto college students with more responses being observed in 4-yr.-olds (see Table 1). A similar trend was observed to stimulus offset in the content condition which could also be characterized as a non-signal event. The consistency of these two trends may suggest that a slight age difference does exist in electrodermal elicitation of orienting responses to stimulus offset. The pattern of cardiac responses to stimulus offset, as noted above, was exactly opposite this trend. This latter finding at least questions the existence of an underlying difference in these autonomic systems which is related to age. Habituation of the orienting response to stimulus offset was not different between the three age groups with either a cardiac or electrodermal measure. That is, even directional differences did not support the hypothesis of slower habituation of the orienting response to stimulus offset among children. The pattern of electrodermal responses elicited in the content and duration conditions replicated those found by Beideman and Stern ( 1971) and Greene, et al. (1974). Task demands were the primary determinants of responses in these two conditions with no reliable age differences. The cardiac measures of elicitation of orienting responses did show some interesting age differences, which have already been described. It was somewhat surprising that faced with a binary decision in the duration condition of 8 sec. or longer than 8 sec. that Ss did not exhibit orienting responses accordingly. Inspection of the data showed only one college S who exhibited orienting responses at this decision point. The process of having all duration Ss count may have interfered with this simplier solution. In any respect task demands were sufficient to control the pattern of orienting response elicitation. The lack of concordance between electrodermal and cardiac measures in psychophysiological research, which also occurred in the present study, has been frequently encountered. In older Ss the cardiac measure was sensitive to any stimulus change while the electrodermal measure was affected by task demand manipulations. It would be interesting to determine whether a cardiac measure
ORIENTING RESPONSES AS A FUNCTION OF AGE AND TASK COMPLEXITY1 ROGER L. GREENE Texrrs Tech Universify Summary.-Age-related differences i n the elicitation and habituation of orienting responses to the onset and offset of stimuli have been suggested by several authors. Eleccrodermal and cardiac orienting responses to the onset and offset of a visual stimulus were measured i n three age groups ( 4 yr., 7 yr., and undergraduate). Each S made one of three judgments: non-signal (observe stimulus), content (co!or of stimulus), and duration (length of time stimulus presented). Few age differences were found in elicitation or habituation of orienting responses to stimulus onset o r offset. There was a trend for elicitation of orienting responses to stimulus offset to be age-related, but the failure to find any other age-related changes made this difference somewhat questionable. Instructions as to the judgment to be made by S were the primary determinants of orienting responses to stimulus onset and offset across all age groups.
Stern (1968) hypothesized that habituation of the "terminal OR [the orienting response to the offset of a stimulus] is intimately tied up with the organism's ability to bind or conceptualize time, while the onset OR is more concerned with the content of the material encompassed by time" (p. 408). In a test of this hypothesis Beideman and Stern (1971) asked college students to judge either the duration or content (pitch) of a tone. They reported that Ss who judged stimulus content produced more orienting responses t o stimulus onset than offset. Those Ss who judged stimulus duration produced as many orienting responses to stimulus onset as offset. The number of orienting responses to stimulus onset did not differ between the t w o groups but the group judging duration showed more orienting responses to stimulus offset than those judging content. They concluded that the orienting response to stimulus onset and offset may be related to "memory storage of the content and duration of a stimulus respectively" (Beideman & Stern, 1971, p. 380). However, Greene, Dengerink, and Staples (1974) in a replication and extension of this study found no direct relationship between orienting responses to stimulus onset and stimulus content, or between orienting responses to stimulus offset and stimulus duration as Stern had postulated. Rather it appeared that the orienting response could be elicited at any point during a stimulus merely by altering the type of instructions which Ss were given. Stern (1968) also reported a pilot study in which orienting responses to the offset of a 6-sec. non-signal tone, a tone to which S attends without making 'This research is based upon a dissertation submitted in partial fulfillment of the requitements for the Ph.D. at Washington State University. The author would like to thank the members of his committee. Garv G. Galbraith and Ronald H. H o ~ k i n s .and ~articularlv for reprints should-be sent to-the author his chairman, Harold A. ~ e n ~ e i i n kRequests . at the Department of Psychology, Texas Tech University, Lubbock, Texas 79409.
544
R. L. GREENE
any response, occurred with much greater frequency and regularity in 6- and 12-yr.-old children than in college students. Six-yr.-olds also gave more orienting responses to the offset of the tone and habituated more slowly than 12-yr.-olds. Scern hypothesized that the orienting response to scimulus offset may be a reflection of the organism's ability to conceptualize time and as such should be highly correlated with measures of attention; these increase as a function of age and experience. In other words, the better the organism is able to conceptualize time, the faster the orienting response to stimulus offset should habituate. He also mentioned (personal communication, 1973) that with a non-signal stimulus Ss may self-instruct themselves and these self-instructions may differ as a function of age. The exact nature of these self-instructions was not made explicit nor was why they should vary as a function of age. The question that remains unanswered at this point is how to explain the age-related differences in orienting responses to stimulus offset which Stern reported. Within a Sokolovian framework the rapidity with which a matchmismatch model of the stimulus is constructed should increase with the age and experience of the organism. Also, as the complexity of the stimulus decreases there should be an increase in the rapidity with which the model is constructed. Thus, habituation of orienting responses should reflect both the age and experience of the organism as well as the complexity of the stimulus. A somewhat similar notion to this latter point has been suggested by Walley and Weiden (1973) who stated that the degree of phasic increase in arousal varies directly with task complexity. The first step in understanding these age-related changes in orienting responses to stimulus onset and offset is a parametric investigation of the variables of age and task complexity. Three ages of Ss ( 4 yr., 7 yr., and undergraduate) and three levels of task complexity (non-signal, content, and duration) were combined factorially. All Ss were presented with a constant visual stimulus which varied in color and duration between trials. The three levels of task complexity involved judging the color or duration of the stimulus or merely watching the stimulus. Electrodermal and cardiac measures of orienting responses were used so that their relationship can be examined. Finally, a dishabituation trial was included to examine the specific aspects of the stimulus to which Ss had habituated. Although the judgments of stimulus content and duration are similar to those used by Beideman and Scern (1973), this experiment was not intended to be a test of Stern's hypothesis that orienting responses to stimulus onset and offset are related to stimulus content and stimulus duration. Greene, et al. ( 1974) found that there were more parsimonious interpretations of the patterns of orienting responses produced by task demands. Instead, these judgments were used as points along a dimension of task complexity, which also allowed for comparisops with these studies.
ORIENTING RESPONSE, AGE, COMPLEXIW
METHOD Sabjectr Forty-five males and 45 females in 3 age groups served as Ss. The first group included 15 male and 15 female college undergraduates enrolled in introductory psychology at Washington State University. Students in these classes volunteer for experiments to earn course credit. The second group of Ss were 15 boys and 15 girls, 7 and 8 yr. old. These children were recruited through friends and acquaintances of the experimenter. The third group of Ss were 15 boys and 15 girls, 4 yr. old. Nineteen of the 4-yr.-olds were obtained through the Washington State University Nursery School. The remainder were recruited through friends and acquaintances of the experimenter. Only 2 parents of the 69 who were contacted refused to allow their children to participate. Three 4-yr.-olds and one 7-yr.-old were replaced because they did not understand the instructions. Nine college students had to be replaced because their cardiac data were not scoreable due to equipment failure during the initial phases of the experiment. During the remainder of the experiment, one college student, one 7-yr.-old, and two 4-yr.-olds had to be replaced because of E's inability to obtain a scoreable cardiac response. All Ss, except che 19 4-yr.-olds tested at the University Nursery School, were tested in an Industrial Acoustics Company soundproof room. The 19 4yr.-olds were tested in an observation room at the Nursery School. During the experiment S sat 0.3 m in front of a 0.63- X 0.63-m wooden box which contained a 0.21- X 0.23-m rear projection screen. A response panel with two response buttons was mounted across the bottom of the wooden box. A light located directly below the rear projection screen indicated when S was to respond. S's responses on the buttons illuminated a panel in the adjoining room, where all the programming and recording apparatus were located. The stimuli were presented by a Kodak Carousel projector. The projector lamp (GE ELH) had a rise time of 270 msec. The slides were constructed from red, blue, and green theatrical gels, which appeared subjectively to be of equal intensity. A Tally tape reader programmed the stimuli and their duration, the response light, and the polygraph signal marker. Silver-silver chloride electrodes (Edelberg, 1967) and a Grass Model 79 polygraph with a 7P1 preamplifier were used to record electrodermal responses. A 7P4 preamplifier was used to record cardiac responses. Pro cedgre Upon arriving at the laboratory each S within his respective age group was randomly assigned to one of 3 conditions. Random assignment of Ss to conditions was constrained so that there was an equal number of male and female Ss within each condition. After S was seated within the soundproof room,
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the electrodermal electrodes were attached to the palm and back of the left hand. T h e cardiac electrodes were attached using standard lead configuration I1 ( Brener, 1967 ) . T h e stimulus series was identical for all 3 groups. T w o hues (red and green) of slides of 2 durations (8 or 16 sec.) were randomly assigned across the 16 trials. During Trial 1 7 a blue slide was presented for 4 sec. For all three groups a variable intertrial interval of 10, 15, or 20 sec. was used. T h e intertrial interval was measured from the onset of the light signaling S to respond to the onset of the next slide. O n the first 16 trials the light signaling S to report his judgment appeared 5 to 1 0 sec. following stimulus offset and remained on until S made a response. S was not required to make any judgment for Trial 17. E recorded S's judgrnencs from the panel onto the polygraph record. There were three experimental condicions within each age: non-signal, content, and duration. In the non-signal condition S was asked to sic quietly and watch the slides. T h e light signaling S co make his judgment was disconnected for this condition. In [he content condition S was asked co judge whether the slides were red or green. T h e light signaling S to make his judgment also illuminated small red and green slides directly above the two response buttons. In the duration condition S was asked to judge whether the slides were of short or long duration. T o enable the children to make this judgment, all Ss in the condition were instructed to count throughout the stimulus duration. Using this procedure S found an approximate number which corresponded to short and long. T h e college Ss were told that Trial 1 would be short and Trial 2 would be long. T h e children were assisced in counting for Trials 1 and 2 and also shown when to push the response button. N o further assistance in counting was given to any S. Some of the children had to be reminded to wait to push or to push the response button. N o assistance in which button to push was given after Trial 2. T h e response buctons were marked by cards.with symbols for short and long, which were taped over the slides on the response panel. For the two younger age groups a second E remained with S throughout the experiment. T h e children selected a small toy as a reward for their participation.
RESULTS Electrodermal Responses
T w o criteria were used to score electrodermal responses as orienting responses. Skin resistance respmses greater than 200 ohms from the prestimulus baseline which occurred between 0.5 and 3.0 sec. after stimulus onset or offset were considered responses. Skin resistance responses were converted to skin conductance responses by the Psychophysiological Data Preparation Program (Greene & Bertilson, 1 9 7 3 ) . This program also computed the frequency and
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amplitude of skin conductance responses as well as the amplitude of skin conductance responses corrected for individual differences in range (Lykken, e t al., 1966). Each of these response measures was averaged into four blocks of four trials/block. Any trial on which S made an incorrect judgment was excluded from the data analysis. Using this criterion 2.8% of the total trials were excluded. T h e analysis of the frequency of skin conductance responses and the amplitude of skin conductance responses corrected for individual differences in range were virtually identical which seemed to preclude the necessity of reporting both measures. The fact that the frequency data were discontinuous, which violates the assumptions of analysis of v~riance,was recognized. However, a separate analysis of the amplitude of skin conductance responses corrected for individual differences in range, which involved continuous data, yielded identical results. Frequency of skin conductance responses will be reported to enhance comparability wich two earlier articles on orienting responses to stimulus offset (Beideman & Stern, 1973; Greene, e t al., 1 9 7 4 ) , which employed frequency measures. A more complete description of the results is presented in Greene (1974). T h e frequency of orienting responses co stimulus onset and offset across the 16 trials in four blocks were used in the data analysis. These data were subjected to an age by sex by condition by response by block analysis of variance. T h e mean frequency of orienting responses by block for each condition are presented in Table 1. The main effects for condition ( F z V s 1 = 18.96), response (1;1,81 = 18.29), and block = 17.08) were significant. The maln effect for age ( F 2 , s l = 2.65) was not reliable. T h e interaction of condition by response by block (Flj,234= 3.34) was significant. This interaction reflected the observation that orienting responses ro stimulus offset habituated in the content and duration conditions and either did not habituate in the non-signal condition or habituated extremely rapidly. In the latter condition orienting responses to stimulus offset were infrequent throughout all blocks. There was no difference in habituation of orienting responses to stimulus onset between the three conditions. All post hoc tests were made wich the Newman-Keuls test for comparison of cell means. Only one comparison of orienting responses to stimulus onset was significant. Orienting responses were more frequent in the content and duration conditions than in the non-signal condition during Block 3. Comparisons of orienting responses to scin~ulusoffset yielded the following significant differences. More responses were observed in the duration condition during Blocks 1 to 4 and in the content condition during Blocks 1 to 3 than in the non-signal condition. More responses were observed in the duration condition during Blocks 2 and 4 than in the content condition. Comparing responses across blocks within conditions, a number of significant differences were found. More orienting responses to stimulus onset were observed in the non-signal condition during Blocks 1 to 3 than to
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R. L. GREENE TABLE 1 MEANFREQUENCY OF ORIENTING AND TERMINAL ORIENTING RESPONSES BY
Age
AGE,CONDITION, AND BLOCK
Block Non-signal
OR* 4 yr.
TOR
Condition Content
OR
TOR
2.70 1.10 3.20 2.70 2.60 1.40 2.40 2.70 1.40 1.80 3.10 2.20 1.80 1.30 1.70 1.90 1.40 2.38 2.13 2.60 7 yr. 2.80 1.20 3.20 2.50 2.30 1.80 0.90 2.80 2.70 0.90 3.10 3 1.50 4 1.40 1.30 2.30 1.80 Total 1.88 1.08 2.33 2.85 College 1 2.60 2.50 0.70 3.30 2 0.50 1.80 1.20 1.60 0.60 1.50 1.00 3 1.50 1.00 1.40 1.10 4 1.90 Total 1.90 0.70 2.30 1.45 'OR, Orienting response; TOR, Terminal orienting response. 1 2 3 4 Total 1 2
Duration OR TOR 2.50 1.60 2.10 2.40 2.15 3.10 2.50 2.20 2.60 2.60 3.10 2.30 2.60 1.60 2.40
2.80 2.90 2.50 2.30 2.63 2.90 3.20 2.80 2.90 2.95 3.40 2.70 2.20 2.20 2.63
stimulus offset. More orienting responses to stimulus onset were observed in the content condition during Blocks 1 and 3 than to scimulus offset. In the duration condition, however, more oriencing responses to stimulus offset were observed during Block 2. The data for the dishabicuacion trial were analyzed by comparing the frequency of skin conductance responses to Trials 16 and 17. These data were subjected to an age by sex by condition by response by trial analysis of variance. The main effects for condition ( F z , 8 1 = 6.62 ), response ( F l , s l = 11.77), and trial ( F l , s l =. 12.36) were significant. Again, the main effect for age ( F Z , ~ ~ = 0.71) was not significant. The interaction of condition by response (FI?,81= 5.67) and the interaction of condition by trial ( F l q s l = 3.20) were both significant, but the interaction of condition by response by trial ( F 2 , 8 1 = 1.95) was not. Mean frequencies of oriencing responses by age and condition for Trials 16 and 17 are presented in Table 2. More responses co stimulus onset than offset were observed in che content condition, while more responses to stimulus offset than onset were observed in che duration condition. Significancly more responses to stimulus offset were observed in the duration condition than in the non-signal condition. The interaction of condition by trial reflected that more responses were observed in the content and duration conditions on Trial 17 than on Trial 16. Significantly more responses were observed in the duration condition than
ORIENTING RESPONSE, AGE, COMPLEXITY TABLE 2 MEANFREQUENCY OF ORIENTING AND T M I N A LORlENTlNG RESPONSES BY AGE AND CONDITION FOR TR~ALS 16 AND 17 Age
4 yr. 7 yr.
College
Trial
16 17 16 17 16 17
Non-signal ORr TOR
Condition Content OR TOR
0.30 0.40 0.30 0.70 0.50 0.90
0.40 0.90 0.50 1.00 0.70 0.90
0.30 0.30 0.40 0.10 0.30 0.00
0.50 0.60 0.30 0.50 0.20 0.50
Duration OR TOR 0.50 0.70 0.70 0.70 0.30 0.50
0.60 0.50 0.80 0.80 0.40 0.70
'OR, Orienting response; TOR, Terminal orienting response. in the non-signal condition on Trial 16. Comparing trials within conditions, significantly more responses were observed in the content condition on Trial 17 than on Trial 16. Cmrdiac R esponser
Heart rate was recorded at 1-sec. intervals for a period of 5 sec. beginning at stimulus onset and offset. Heart-rate level at stimulus onset and offset was not significantly different between conditions or condition within ages. There were substantial differences, however, in mean tonic level heart rate in beats per minute between the three age groups: college (75.3), 7-yr.-old (83.2), and 4-yr.-old (100.6). The heart-rate data were analyzed as a change score expressed as a difference score from the pre-onset or pre-offset baseline. A separate analysis of the heart-rate change scores corrected for individual differences in range as well as an analysis of covariance yielded similar results and will not be described. The mean heart-rate change scores were subjected to an age by sex by condition by response by block by time analysis of variance. Only the main = 13.77) was significant. Neither the main effect for effect for time (F4,324 age nor condition was reliable. The interaction of age by condition by response by time ( F l f i , ~ = 4 2.46) was significant. To facilitate interpretation of this interaction, separate analyses were conducted within each condition, and significant effects were subjected to trend analysis (Wilson, 1974). In the non-signal condition there were no significant main effects or interaction terms. The small change in mean heart rate was similar to stimulus onset and offset in all three age groups. If cardiac orienting responses are defined as heart-rate deceleration (Graham & Clifton, 1966 ) , orienting responses were displayed by 7-yr.-olds and college students to stimulus onset and by 4-yr.-olds and college students to stimulus offset. These figures are not displayed since there were no significant effects.
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-2.00
-
COLLEGE FOUR SEVEN
SECONDS
FIG. 1.
Mean onset of heart-rate change
by age for content
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COLLEGE FOUR SEVEN
SECONDS
FIG. 2. Mean offset of heart-rate change by age for content
In the content condition the age by response by time interaction ( F B . l o a= 2.45) was significant. The mean heart-rate change scores for this interaction = 4.32) and cubic trends are illustrated in Figs. 1 and 2. Both the linear (F:..'7 = 13.65) within the interaction of age by time were significant to stimulus onset. T h e same two trends were also reliable within the main effect of ; 14.35) and cubic trends ( F l q s 7 = 10.33) within cime. Only the linear ( F I n 2 = the main effect of time were significant to stimul~lsoffset. None of the trends within the age by block by time interaction was reliable either to stimulus onset or offset. Inspection of Fig. 1 and a separate contrast of college students with 7- and 4-yr.-olds showed that the cubic trend was more pronounced to stimulus onset in the college students. T w o other findings should be noted: first, habituation either did not occur or occurred very rapidly within the first few trials; and second, 4-yr.-olds did not display orienting responses to stimulus onset or offset, while 7-yr.-olds and college students displayed orienting responses to both. In the duration condition the interaction of age by response by time ( F s . l o s = 2.26) was also significant. Mean heart-rate change scores for this interaction are illustrated in Figs. 3 and 4. Trend analysis revealed that only the linear = 4.56) and cubic trends ( F 1 , 2 i = 6.11) within the main effect of time were significant to stimulus onset. Both the linear ( F , , 2 i = 6.07) and cubic trends ( F 2 , 2 i = 4.57) within the interaction of age by time were significant to stimulus offset. The cubic trend within the main effect of time was also significant to stimulus offset. Again, none of the trends within the age by block by cime interaction was reliable either to stimulus onset or offset. Four-yr.-olds again did not display orienting responses to stimulus onset or offset, while both
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-COLLEGE c--r FOUR -SEVEN
SECONDS
SECONDS
FIG. 3. Mean onset of heart-rare change by age for duration
FIG. 4. Mean offset of heart-rate change by age for duration
7-yr.-olds and college students displayed orienting responses to stimulus onset, s and 7-yr.-olds displayed oriencing responses to s c i m u l ~ ~offset. T h e data for the dishabituation trial were analyzed by comparing mean heart-rate change scores to Trials 16 and 17. Since the stimulus for Trial 17 lasted only 4 sec., heart rate was only recorded for a period of 4 sec. following stimulus onset and offset. These data were subjected ro an age by sex by condition by response t y trial by time analysis of variance. None of the interactions of a p r i o ~ iinterest was significant. Only the interaction of trial by time (P3,24:1 = 2.74) and the interaction of condition by response by time (FD,2.1R = 2.48) were significant. There was no systematic pattern to the cardiac orienting responses elicited during Trials 16 and 17. orienting responses did occur less frequently in the 4-yr.-olds than in the two older age groups.
DISCUSSION Stern ( 1968) reported that electrodermal orienting responses to the offset of a non-signal tone were more frequent in 6- and 12-yr.-old children than in college students. H e also reported that habituation of orienting responses to stimulus offset was slower in children than in college students. The non-signal condition in the present experiment, however, did not replicate these age differences. In fact there were no significant age differences in elicitation of orienting responses to stimulus onset or offset with the electrodermal measure. Habituation of the electrodermal orienting response to stimulus offset either did nor occur or occurred very rapidly in all three groups. There were significant age differences in elicitation of orienting responses to stimulus onset and offset with the cardiac measure. T h e general pattern was one in which orienting responses
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were elicited to any stimulus change in the two older age groups, while 4-yr.-olds displayed defensive responses rather than orienting responses to stimulus change. That is, college students and 7-yr.-olds displayed cardiac orienting responses to stimulus onset and offset in all three conditions, while 4-yr.-olds displayed only defensive responses. Orienting response to stimulus offset, rather than being more frequent in younger children as Stern found with an electrodermal measure, did not occur in the 4-yr.-olds with a cardiac measure. Habituation of the cardiac orienting response either did not occur or occurred very rapidly in all three age groups in all conditions. The trend of the age differences within the non-signal condition with the electrodermal measure, however, was identical to that reported by Stern. Frequency of orienting responses to stimulus offset was ordered from 4-~r.-oldsto college students with more responses being observed in 4-yr.-olds (see Table 1). A similar trend was observed to stimulus offset in the content condition which could also be characterized as a non-signal event. The consistency of these two trends may suggest that a slight age difference does exist in electrodermal elicitation of orienting responses to stimulus offset. The pattern of cardiac responses to stimulus offset, as noted above, was exactly opposite this trend. This latter finding at least questions the existence of an underlying difference in these autonomic systems which is related to age. Habituation of the orienting response to stimulus offset was not different between the three age groups with either a cardiac or electrodermal measure. That is, even directional differences did not support the hypothesis of slower habituation of the orienting response to stimulus offset among children. The pattern of electrodermal responses elicited in the content and duration conditions replicated those found by Beideman and Stern ( 1971) and Greene, et al. (1974). Task demands were the primary determinants of responses in these two conditions with no reliable age differences. The cardiac measures of elicitation of orienting responses did show some interesting age differences, which have already been described. It was somewhat surprising that faced with a binary decision in the duration condition of 8 sec. or longer than 8 sec. that Ss did not exhibit orienting responses accordingly. Inspection of the data showed only one college S who exhibited orienting responses at this decision point. The process of having all duration Ss count may have interfered with this simplier solution. In any respect task demands were sufficient to control the pattern of orienting response elicitation. The lack of concordance between electrodermal and cardiac measures in psychophysiological research, which also occurred in the present study, has been frequently encountered. In older Ss the cardiac measure was sensitive to any stimulus change while the electrodermal measure was affected by task demand manipulations. It would be interesting to determine whether a cardiac measure
