BRAIN
AND
LANGUAGE
Bilateral
8,
81-91 (1979)
Tachistoscopic Perception, and Lateral i ty
Handedness,
JOSEPHSCHMULLERANDROBERTAGOODMAN Clark University
Right-handed, familial left-handed, and nonfamilial left-handed males and females reported high- or low-imagery words which were located to the left and right of fixation in bilateral tachistoscopic displays. On each trial, an arrowhead appeared in the center of the display. The arrowhead pointed to either the left or the right half-field, indicating the order of report. Right-handers reported more accurately from the right half-field, and familial left-handers reported more accurately from the left half-field. The order of report results showed that right-handers were similar to nonfamilial left-handers; for left half-field presentation, both groups were more accurate when the arrowhead pointed to the left than when it pointed to the right (i.e., first report was more accurate than second report). There was a main effect of word imagery, but this factor did not interact with visual half-field. Thus, there was no evidence that representations of high-imagery words are lateralized differently than representations of low-imagery words. The results are discussed with respect to lateralization of memory for verbal material.
This study applied a new experimental paradigm to the study of cerebral asymmetry for the recognition of tachistoscopically presented words. Many studies in this area have employed a procedure formulated by McKeever and Huling (1971), in which a digit is presented at the fixation point in the stimulus field of a tachistoscope, and the subject is required to report the digit before reporting information from each visual half-field of a bilateral display presented at the same time as the digit. This is done to ensure that the observer maintains fixation in the center of the visual field. A problem with this procedure is that information from the briefly presented display is rapidly decaying from sensory storage while the subject reports the fixation digit. Furthermore, while a word is being reported from one visual half-field, information may be lost from the trace in the other half-field. Because of reading habits, report tends to begin with the This paper was aided immeasurably by the insights of Valerie F. Reyna. Errors and inconsistencies which remain are the fault of the authors. Reprint requests should be addressed to Joseph Schmuller, Department of Psychology, Clark University, Worcester, MA 01610. 81 0093-934X/79/040081-11$02.00/O Copyright @ 1979 by Academic Press, Inc. All rights of reproduction in any form reserved.
82
SCHMULLER
AND GOODMAN
left half-field (Mackavey, Curcio, & Rosen, 1973, and information may be lost from the right visual half-field before it can be reported. While it is true that a right half-field advantage is often found with the fixation-digit procedure (indicating that the left hemisphere is dominant), the difficulties cited may obscure the true magnitude of this advantage. Also, since there is no control for order of report, this procedure cannot reveal how much, if any, of a visual half-field advantage is due to loss from storage. Typical findings from work in tachistoscopic perception substantiate the need to consider loss from storage. When subjects are asked to report all the letters of a briefly presented multiletter display, they usually say that they see more letters than they can report (e.g., Pillsbury, 1897). Some of the perceived letters seem to be “lost” while others are being reported. Sperling (1960) asked subjects to report portions of displays; on each trial, the offset of a briefly presented three-row display was followed by a tone whose pitch indicated the row to be reported. Estimates of the number of characters perceived were based on the number of characters correctly reported per row times the number of rows. These estimates were consistently greater than the number of characters that subjects could report when they were asked to report the entire display. Also, performance sharply declined with tone delay, indicating the brief duration of the stored representation of the display. The paradigm used in the present experiment controlled the order of report. Subjects were required to fixate on a point in the center of the preexposure field of a two-field tachistoscope. At the center of the stimulus field, an arrowhead appeared concurrent with the onset and offset of a bilateral display. The arrowhead pointed either to the left or to the right; its direction indicated which of the two half-fields was to be reported first. This differs from previous work in that only the information from the visual half-fields was reported, rather than this information and a fixation digit. Subjects had to maintain fixation in order to report in the correct sequence. There are two advantages to this paradigm. First, report in the order specified by the arrowhead indicated maintenance of fixation without requiring the subject to report an extra stimulus element. Second, since the order of report from the visual half-fields is specified, data can be gathered concerning loss of stored information in each of the hemispheres. As a first investigation with this paradigm, we studied tachistoscopic perception in right-handers, and in familial and nonfamilial left-handers, of high- and low-imagery words. Previous work on cerebral dominance and the cognitive processes of left-handers has been equivocal. Bryden (1965) found that left-handers identified digits presented to the left ear slightly better than digits presented to the right ear, while right-handers exhibited a significant right ear advantage. In a tachistoscopic letter recognition task, left-handers showed no visual half-field differences,
BILATERAL
TACHISTOSCOPIC
PERCEPTION
83
while right-handers had a significant right half-field advantage. Other laterality effects were uncovered when the left-handers were divided into familial (members of families with at least one other left-handed member) and nonfamilial subgroups. Familial left-handers showed better recognition for right ear presentation and right visual half-field presentation, while nonfamilials showed no differences. Zurif and Bryden (1969), however, found that nonfamilial left-handers showed significant right ear and right visual half-field advantages. Although these findings appear contradictory, division of left-handed subjects into familial and nonfamilial subgroups has produced different patterns of responding. Therefore, we included this distinction in the present study. With respect to word imagery, recent studies (Ellis & Shepherd, 1974; Hines, 1976) have shown that for right-handed observers, abstractnessconcreteness interacts with visual half-field. Ellis and Shepherd found an advantage for concrete words over abstract words in the left visual halffield, but no such differences for right visual half-field presentation; they took this result as a possible indication that high-imagery nouns are bilaterally represented. Hines found that with high-frequency words, abstract (low-imagery) nouns show an advantage over concrete nouns for right half-field presentation, but concrete (high-imagery) nouns show a slight advantage over abstract nouns for left half-field presentation. Both studies used bilateral displays (although Hines also used several other types of displays), but neither study controlled the order of report. METHOD The subjects were 24 undergraduate volunteers at Clark University, of which one-third were right-handed, one-third were familial left-handers, and one-third were nonfamilial left-handers. A familial left-handed subject was defined as a left-hander whose immediate family has at least one other left-handed member. (Note: With this as our criterion of familiality, no nonfamilial right-handers-i.e., right-handers from completely left-handed families-were available to us.) None of the right-handed subjects had any left-handers in their immediate families. Half of the subjects were male. All subjects had 20120vision, normal or corrected. Stimuli. The stimuli were 40 four- and five-letter nouns taken from the list of Paivio, Yuille, and Madigan (1968). Twenty of these nouns were high-imagery words and twenty were low-imagery words (above 6.37 and below 4.13, respectively, on the scale of Paivio et al.). All were high-frequency words according to the Thorndike and Lorge (1944) frequency count. Each high-imagery word was paired with a low-imagery word, and each of the resulting 20 pairs was printed on a white 5 x 8 card in uppercase 128530C Prestype. The center of each word was 2.54 cm from the center of the card; the viewing distance was 78.74 cm, so that the distance from the center of the card to the center of a word subtended 1.8” of visual angle. (This angle was used because of the size of the tachistoscope viewing screen.) Another set of 20 cards was prepared such that none of the paired words from the first set was re-paired in the second set. Also, a word appearing on one side of the center of the first set was put on the opposite side in the second set. In the entire set of 40 cards, half the cards had high-imagery words on the left and low-imagery words on the right, while the reverse was true for the other half. On each card, an arrowhead-indicator was centered between the Subjects.
84
SCHMULLER
FIRE
AND GOODMAN
AND
LANGUAGE
Bilateral
8,
81-91 (1979)
Tachistoscopic Perception, and Lateral i ty
Handedness,
JOSEPHSCHMULLERANDROBERTAGOODMAN Clark University
Right-handed, familial left-handed, and nonfamilial left-handed males and females reported high- or low-imagery words which were located to the left and right of fixation in bilateral tachistoscopic displays. On each trial, an arrowhead appeared in the center of the display. The arrowhead pointed to either the left or the right half-field, indicating the order of report. Right-handers reported more accurately from the right half-field, and familial left-handers reported more accurately from the left half-field. The order of report results showed that right-handers were similar to nonfamilial left-handers; for left half-field presentation, both groups were more accurate when the arrowhead pointed to the left than when it pointed to the right (i.e., first report was more accurate than second report). There was a main effect of word imagery, but this factor did not interact with visual half-field. Thus, there was no evidence that representations of high-imagery words are lateralized differently than representations of low-imagery words. The results are discussed with respect to lateralization of memory for verbal material.
This study applied a new experimental paradigm to the study of cerebral asymmetry for the recognition of tachistoscopically presented words. Many studies in this area have employed a procedure formulated by McKeever and Huling (1971), in which a digit is presented at the fixation point in the stimulus field of a tachistoscope, and the subject is required to report the digit before reporting information from each visual half-field of a bilateral display presented at the same time as the digit. This is done to ensure that the observer maintains fixation in the center of the visual field. A problem with this procedure is that information from the briefly presented display is rapidly decaying from sensory storage while the subject reports the fixation digit. Furthermore, while a word is being reported from one visual half-field, information may be lost from the trace in the other half-field. Because of reading habits, report tends to begin with the This paper was aided immeasurably by the insights of Valerie F. Reyna. Errors and inconsistencies which remain are the fault of the authors. Reprint requests should be addressed to Joseph Schmuller, Department of Psychology, Clark University, Worcester, MA 01610. 81 0093-934X/79/040081-11$02.00/O Copyright @ 1979 by Academic Press, Inc. All rights of reproduction in any form reserved.
82
SCHMULLER
AND GOODMAN
left half-field (Mackavey, Curcio, & Rosen, 1973, and information may be lost from the right visual half-field before it can be reported. While it is true that a right half-field advantage is often found with the fixation-digit procedure (indicating that the left hemisphere is dominant), the difficulties cited may obscure the true magnitude of this advantage. Also, since there is no control for order of report, this procedure cannot reveal how much, if any, of a visual half-field advantage is due to loss from storage. Typical findings from work in tachistoscopic perception substantiate the need to consider loss from storage. When subjects are asked to report all the letters of a briefly presented multiletter display, they usually say that they see more letters than they can report (e.g., Pillsbury, 1897). Some of the perceived letters seem to be “lost” while others are being reported. Sperling (1960) asked subjects to report portions of displays; on each trial, the offset of a briefly presented three-row display was followed by a tone whose pitch indicated the row to be reported. Estimates of the number of characters perceived were based on the number of characters correctly reported per row times the number of rows. These estimates were consistently greater than the number of characters that subjects could report when they were asked to report the entire display. Also, performance sharply declined with tone delay, indicating the brief duration of the stored representation of the display. The paradigm used in the present experiment controlled the order of report. Subjects were required to fixate on a point in the center of the preexposure field of a two-field tachistoscope. At the center of the stimulus field, an arrowhead appeared concurrent with the onset and offset of a bilateral display. The arrowhead pointed either to the left or to the right; its direction indicated which of the two half-fields was to be reported first. This differs from previous work in that only the information from the visual half-fields was reported, rather than this information and a fixation digit. Subjects had to maintain fixation in order to report in the correct sequence. There are two advantages to this paradigm. First, report in the order specified by the arrowhead indicated maintenance of fixation without requiring the subject to report an extra stimulus element. Second, since the order of report from the visual half-fields is specified, data can be gathered concerning loss of stored information in each of the hemispheres. As a first investigation with this paradigm, we studied tachistoscopic perception in right-handers, and in familial and nonfamilial left-handers, of high- and low-imagery words. Previous work on cerebral dominance and the cognitive processes of left-handers has been equivocal. Bryden (1965) found that left-handers identified digits presented to the left ear slightly better than digits presented to the right ear, while right-handers exhibited a significant right ear advantage. In a tachistoscopic letter recognition task, left-handers showed no visual half-field differences,
BILATERAL
TACHISTOSCOPIC
PERCEPTION
83
while right-handers had a significant right half-field advantage. Other laterality effects were uncovered when the left-handers were divided into familial (members of families with at least one other left-handed member) and nonfamilial subgroups. Familial left-handers showed better recognition for right ear presentation and right visual half-field presentation, while nonfamilials showed no differences. Zurif and Bryden (1969), however, found that nonfamilial left-handers showed significant right ear and right visual half-field advantages. Although these findings appear contradictory, division of left-handed subjects into familial and nonfamilial subgroups has produced different patterns of responding. Therefore, we included this distinction in the present study. With respect to word imagery, recent studies (Ellis & Shepherd, 1974; Hines, 1976) have shown that for right-handed observers, abstractnessconcreteness interacts with visual half-field. Ellis and Shepherd found an advantage for concrete words over abstract words in the left visual halffield, but no such differences for right visual half-field presentation; they took this result as a possible indication that high-imagery nouns are bilaterally represented. Hines found that with high-frequency words, abstract (low-imagery) nouns show an advantage over concrete nouns for right half-field presentation, but concrete (high-imagery) nouns show a slight advantage over abstract nouns for left half-field presentation. Both studies used bilateral displays (although Hines also used several other types of displays), but neither study controlled the order of report. METHOD The subjects were 24 undergraduate volunteers at Clark University, of which one-third were right-handed, one-third were familial left-handers, and one-third were nonfamilial left-handers. A familial left-handed subject was defined as a left-hander whose immediate family has at least one other left-handed member. (Note: With this as our criterion of familiality, no nonfamilial right-handers-i.e., right-handers from completely left-handed families-were available to us.) None of the right-handed subjects had any left-handers in their immediate families. Half of the subjects were male. All subjects had 20120vision, normal or corrected. Stimuli. The stimuli were 40 four- and five-letter nouns taken from the list of Paivio, Yuille, and Madigan (1968). Twenty of these nouns were high-imagery words and twenty were low-imagery words (above 6.37 and below 4.13, respectively, on the scale of Paivio et al.). All were high-frequency words according to the Thorndike and Lorge (1944) frequency count. Each high-imagery word was paired with a low-imagery word, and each of the resulting 20 pairs was printed on a white 5 x 8 card in uppercase 128530C Prestype. The center of each word was 2.54 cm from the center of the card; the viewing distance was 78.74 cm, so that the distance from the center of the card to the center of a word subtended 1.8” of visual angle. (This angle was used because of the size of the tachistoscope viewing screen.) Another set of 20 cards was prepared such that none of the paired words from the first set was re-paired in the second set. Also, a word appearing on one side of the center of the first set was put on the opposite side in the second set. In the entire set of 40 cards, half the cards had high-imagery words on the left and low-imagery words on the right, while the reverse was true for the other half. On each card, an arrowhead-indicator was centered between the Subjects.
84
SCHMULLER
FIRE
AND GOODMAN
