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Visual Field Recognition Memory for Right-Handed Females as a Function of Familial Handedness
VISUAL FIELD RECOGNITION MEMORY FOR RIGHT-HANDED FEMALES AS A FUNCTION OF FAMILIAL HANDEDNESS I
H. Julia Hannay and Daniel R. Malone (Department of Psychology, Auburn University)
Several studies support the concept of less complete lateralization of linguistic abilities in the left hemisphere and spatial abilities in the right hemisphere of females. For instances, with neurological patients, Lansdell (1961) found that left temporal lobe surgery disrupted only the performance of males on the Gorham's Proverbs Test. Analogously, Lansdell (1962) reported that right hemisphere lesions led to a drop in scores for males but not for females on the Graves Design Judgement Test. McGlone and Kertesz (1974) also found that right hemisphere damage resulted in negligibly lower scores for females on the Block Design subtest of the Wechsler Adult Intelligence Scale but significantly lower scores for males. Research findings with normal subjects are somewhat in accord. On a dot enumeration task, an equal number of females showed left and right visual field superiorities whereas a clear majority of males showed a left visual field superiority (McGlone and Davidson, 1973). Kimura (1969) reported a significant left visual field superiority for localization of a dot in a square or circular array by males. Females also obtained a significant left visual field superiority for dot localization with a circular array but a slight right visual field superiority with a square array. Hannay and Malone (1975) attempted to determine the relative contribution of reception and memory processes to the right visual field superiority for linguistic material generally obtained with normal right-handed males and females. Three letter nonsense words were presented unilaterally and vertically in the left and right visual fields for very short durations. Following memory intervals of 0, 5 or 10 sec., a duplicate of the test stimulus or a highly similar stimulus (differing by the middle letter) was presented in central vision and the subject stated whether this stimulus was the same as the test stimulus. Males showed a slight though non-significant left visual I This investigation was supported by Research Grant-In-Aid 74-79 awarded to the senior author by Auburn University.
Cortex (1976) 12, 41-48.
42
H.
J.
Hannay and D. R. Malone
field superIorIty with the 0 sec. memory interval indicating hemispheric equality in reception of linguistic material. Clear right visual field superiorities with the 5 and 10 sec. memory intervals supported greater left hemisphere involvement in retention of verbal material. Furthermore, an optimal interval for retention of verbal material was suggested since the right visual field superiority was greatest with the 5-sec. interval, decreasing as the interval was increased to 10 sec. Females obtained non-significant right visual field superiorities with the 0 and 10 sec. memory intervals and a non-significant left visual field superiority with the 5 sec. interval. A possible interpretation of these findings is that in females the left and right hemispheres are not particularly specialized for reception or memory of linguistic material. But, on the basis of the memory function obtained with males, right visual field superiorities, though smaller, would be predicted for females with all intervals, the 5 sec. memory interval producing the greatest field difference. Satz, Achenbach and Fennell (1967) have found that 33% of righthanders obtaining a right ear superiority on a dichotic listening task reported left-handed family members while 56% of right-handers obtaining a left ear superiority reported left-handed family members. Similarly, Zurif and Bryden (1969) and Hecaen and Sauguet (1971) have demonstrated that familial handedness is a determinant of hemispheric asymmetry of function in lefthanders. Information concerning the handedness of parents and siblings participating in the study by Hannay and Malone (1975) was available since subjects had filled out the Neurosensory Center Handedness Questionnaire (Benton, Meyers and Polder, 1962). Examination of these records revealed that all of the male subjects were familial right-handers; that is, their parents and siblings were also right-handed. However, one third of the female subjects were nonfamilial right-handers having at least one left-handed parent or sibling. It seems reasonable, then, to suggest that left-handedness in the immediate family of some of the females might have contributed to the rather unusual field effects for that group. Consideration of the studies in which sex or familial handedness were variables leads to specific predictions concerning the performance of righthanded females on laterality tasks involving linguistic material: (1) Familial right-handed females should exhibit right visual field superiorities similar to those reported for males. The laterality effects should, however, be smaller. (2) Non-familial right-handed females should exhibit visual field superiorities of similar magnitude to those obtained by familial right-handed females, in the left rather than the right visual field. The present study was designed to investigate these predictions with the stimuli previously employed by Hannay and Malone (1975).
Visual field recognition memory
43
MATERIALS AND METHOD
Subjects
Thirty right-handed female undergraduates, aged 18-29 years and enrolled in psychology courses at Auburn University, volunteered for the study. A modification of the handedness questionnaire used by Benton, Meyers and Polder (1962) was used to determine handedness of the subject and familial handedness. Twenty-seven of the subjects classified themselves as strongly right-handed and three as moderately right-handed though all reported use .of the right hand for at least 8 of 10 hand activities. Fifteen females with only right-handed parents and siblings formed the familial right-handed group. Fifteen females with a lefthanded parent or sibling formed the non-familial right-handed group. A Bausch and Lomb Modified Orthorater was used to determine visual characteristics. All subjects demonstrated 20/25 or better acuity in each eye and both eyes together, normal vertical phoria and normal lateral phoria, all at both near and far distances. Stimuli
Twenty-four three letter nonsense words were selected from the CVC list of Noble (1961). The four pretest stimuli and their respective incorrect foils had a mean association value of 2.10 (S.D. = .054). The eight test stimuli and their respective incorrect foils had a mean rated association value of 2.06 (S.D. = .049). Test stimuli and their incorrect foils differed by the middle letter. Prestype dry transfer lettering (Helvetica 1320 - 24 CLN) was used to print black letters vertically on white stimulus cards. The words subtended a visual angle of about 1° 40' vertically. Pretest stimuli were centered on the cards. Test stimuli appeared 2° either to the left or right of a central fixation point. Apparatus
A Gerbrands 4-field tachistoscope model T-4A with an automatic card changer and three semiautomatic card backs was employed. The stimuli were illuminated in one field. The second field contained a small black circle and the third field, a small black dot, both centrally located. The fourth field contained a blank white card. The fields were aligned and maintained at a luminance of approximately 20 cd/m2 • Procedure
The experiment consisted of two parts: a pretest task to obtain the stimulus exposure duration for each subject and a test task to determine the visual field effects for the nonsense words. At the beginning of every trial, the subject fixated on a small black circle in the center of a lighted screen. The black circle was replaced by a small black dot which served as a warning signal. Two seconds later the dot disappeared and a stimulus was presented. During the pretest task, the nonsense words appeared in central vision. The subject immediately looked away from the viewer and stated whether the nonsense word on a card displayed by the experimenter was the same as (or differed from) the previously presented word. In a trial block, each of the four stimuli was presented twice, followed once by a correct foil (the stimulus) and followed once by an incorrect foil. The pretest task consisted of 5 blocks of 8 trials. The stimulus duration was
44
H. ]. Hannay and D. R. Malone
varied over trial blocks according to the rules of Block Up and Down, TwoInterval Forced-Choice procedure (Campbell, 1963) as modified by Hannay (1972). The first trial block constituted practice judgments and the responses were discarded. A straight line relating the proportion of correct responses for trial blocks to the stimulus duration was fitted to the data of the last four trial blocks by visual inspection and the duration expected to produce .75 proportion of correct responses was determined. For the test task nonsense words were presented in the left or right visual field at the previously computed duration and a memory interval intervened between stimulus and response. Following a sec. memory interval the subject immediately looked away from the viewer to a foil displayed by the experimenter, stating whether the nonsense word was the same as the previously presented stimulus. With 5 and 10 sec. memory intervals, the subject continued to look at a blank, white, lighted screen after stimulus presentation until the fixation circle reappeared at the end of the interval. Then the subject made the samedifferent response to a foil. The test task consisted of three blocks of 32 trials differing by the duration of the memory interval (0, 5 or 10 sec.). Within a trial block, each of the eight nonsense words was presented twice in the left and twice in the right visual field, followed by the correct and incorrect foils once. A different random order was prepared for each .block but the same random orders were used throughout the experiment. Three orders of presentation of the memory intervals were used (0, 10, 5; 5, 0, 10; 10, 5, 0). Each order was administered to 5 familial and 5 non-familial right-handed females .
°
RESULTS
The stimulus exposure duration ranged from 5-28 msec. for the familial right-handers (mean = 11 msec.) and from 7-15 msec. for the non-familial right-hander (mean = 11 msec.). The familial right-handers were correct on 76.9 % of the test trials. The non-familial right-handers were correct on 74.9% of the test trials. The procedure for obtaining the stimulus duration for each subject thus produced comparable performance for both groups. The dependent measure was the number of correct responses for each subject as a function of visual field and memory interval. An analysis of variance was completed in which visual field and memory interval were within subject factors. Familial handedness and order of presentation of memory intervals were between subject factors. More nonsense words were correctly recognized in the RVF than in the LVF (Table I) but the RVF superiority was non-significant (F = 1.36, df 1, 24). Interactions between the variables visual field, memory interval and familial handedness were all statistically non-significant. Determination of the statistical significance of visual field differences at each memory interval for both groups was the major concern of this study. Where the overall F test is non-significant, orthogonal planned comparisons are still justified (Lindmann, 1974). These planned comparisons were made using the appropriate errorterm (MS within fields) from the overall analysis
Visual field recognition memory TABLE
45
I
Mean Number of Correct Nonsense Word Recognitions in the Left and Right Visual Fields for Familial and Non-Familial Female Right-Handers as a Function of the Memory Interval
Memory interval (sec.)
LVF
RVF
(RVF-LVF)
LVF
RVF
0
12040
12.60
0.20
11.93
11.53
-0040
5
11.47
12.80
1.33*
11040
11.20
-0.20
10
12.20
12.33
0.13
11.67
12.67
1.00
XML
12.02
12.58
0.56
11.47
12.00
0.53
* p
Non-familial
Familial
(RVF-LVF)
< .05
in a one-tailed test of significance. The familial right-handers demonstrated a significant right visual field superiority with the 5 sec. memory interval (t = 1.901 df = 24, P < .05). A slight and non-significant right visual superiority was obtained with the 0 sec. memory interval (t = .297, df = 24) and the 10 sec. memory interval (t = .198, df = 24). The non-familial right-handers demonstrated a slight non-significant left visual superiority with the 0 sec. memory interval (t = .594, df = 24) and the 5 sec. memory interval (t = .297, df = 24). A non-significant right visual field superiority followed the 10 sec. memory interval (t = 1.486, df = 24). Figure 1 shows the visual field superiorities for both groups as a function of memory interval. Accuracy of recognition did not vary significantly with the duration of the memory interval (F = 1.04, df = 2, 48). The order of presentation of
1.5
- - Familial
+---+ Nonfamilial 1.0 u..
> -'
IX I
0.5
u..
>
""
IX
0
5
---------
-0.5
--+/
/
·----Memory Interval (sec.)
Fig. 1 - Differences in visual field recognition scores for females as a functions of memory interval and familial handedness.
46
H.
J. Hannay
and D. R. Malone
the memory intervals did not affect the visual field differences (F = 0.12, df = 2, 48). Ten of the familial right-handers and seven of the nonfamilial righthanders showed an overall right visual field superiority. Four of both the familial and non-familial right-handers demonstrated a greater accuracy of recognition in the left visual field. One of the familial right-handers and four of the non-familial right-handers showed no overall field differences.
DISCUSSION
The procedure was identical to that of Hannay and Malone (1975) with one exception. The pretest task consisted of five trial blocks rather than eight. The exposure duration determined with this task was expected to produce 75% correct responses when the stimuli were presented in the left and right visual fields. In the previous study performance levels were 715% and 73% correct responses for males and females respectively. Performance of the females in the present study was remarkably close to these values and suggests that the pretest procedure can be shortened with no loss of precision. In general, predictions concerning the performance of familial right-handed females were supported. Linguistic material was recognized more accurately in the right visual field. Reception of linguistic material appears to be accomplished equally well by both hemispheres as indicated by the nonsignificant field effect with the immediate response. The marginally significant right visual field superiority with the 5 sec. memory interval is indicative of more accurate retention of linguistic material by the left hemisphere, at lea.st over relatively short intervals. For familial right-handed males Hannay and Malone (1975) reported a highly significant right visual field superiority with the 5 sec. interval (p < .005) and a slightly significant right visual field superiority with the 10 sec. interval (p < .05). If linguistic functions are less completely lateralized in females, then familial right-handed females should exhibit similar but smaller right visual field superiorities, the largest field difference occurring with the 5 sec. interval. These are precisely the findings. Predictions concerning the performance of non-familial right-handed females were not upheld. Performance similar to that of the familial righthand~rs, with the superiorities in the left visual field, was expected. Instead, no significant visual field effects were obtained. Recently, Varney and Benton (1975) examined tactile perception of direction, a spatial function presumably subserved by the right hemisphere. The usual left hand superiority for right-handers was demonstrated by 74% of the familial right-handers, 67% of right-handers with a left-handed sibling,
Visual field recognition memory
47
and 40% of right-handers with a left-handed parent. It seems that hand preference of parents is a stronger determinant of performance on a tactile laterality task than handedness of siblings. This factor was not controlled in the present study. Clearly, familial handedness is an important variable. The unusual field effects reported for females in the previous study (Hannay and Malone, 1975) probably can be attributed to a lack of control over this variable in subject selection. Both sex and familial handedness must be considered in research on cerebral asymmetry of function. These factors and factors which are not yet identified probably influence performance on tachistoscopic tasks, dichotic listening tasks and tactile tasks in very complex ways. SUMMARY
Recognition memory for nonsense words presented vertically and unilaterally in the left and right visual fields was investigated in right-handed females as a function of the memory interval and familial handedness. The subject decided whether another nonsense word presented in central vision after memory intervals of 0, 5 or 10 sec. was the same as the stimulus word. The exposure duration producing a recognition accuracy of about 75% for each subject was employed and ranged from 5 to 28 msec. Right-handed females with only right-handed family members demonstrated right visual field superiorities indicative of a slight left hemisphere specialization for memory but not for reception of verbal material. Field superiorities obtained for right-handed females with a left-handed parent or sibling were not significant. In general, less complete lateralization of linguistic function in females was indicated and the importance of familial handedness in cerebral asymmetry of function was confirmed. Acknowledgements. The authors wish to thank Judith Rogers and Maria Puente-Duany for their invaluable assistance in assessing subjects and obtaining the data reported in this study. REFERENCES BENTON, A. L., MEYERS, R., and POLDER, G. (1962) Some aspects of handedness, "Psychiat. Neurol.," 144, 321-337. CAMPBELL, R. A. (1963) Detection of a noise signal of varying duration, "J. Acoust. Soc. Amer.," 35, 1732-1736. HANNAY, H. J. (1972) Age and the time-intensity reciprocity relation for two temporally separated flashes of light, Ph. D. Dissertation, University of Iowa. - , and MALONE, D. R. (1976) Visual field effects and short-term memory for verbal material, "Neuropsychologia," (in press). HECAEN, H., and SAUGUET, J. (1971) Cerebral dominance in left-handed sub;ects, "Cortex," 7, 19-48. KIMURA, D. (1969) Spatial localization in the left and right visual field, "Can. J. Psychol.," 23, 445-458. LANSDELL, H. (1961) The effect of neurosurgery on a test of proverbs, "Amer. Psychol.," 16, 448. (1962) A sex differenc(! in effect of temporal-lobe neurosurgery on design preference, "Nature," 194, 852-854.
48
H. f. Hannay and D. R. Malone
LINDMAN, H. R. (1974) Analysis of Variance in Complex Experimental Designs, Freeman, San Francisco. MCGLONE, ]., and DAVIDSON, W. (1973) The relation between cerebral speech laterality and spatial ability with special reference to sex and hand preference, "Neuropsychologia," 11, 105-113. and KERTESZ, A. (1974) Sex differences in cerebral processing of visuospatial tasks, "Cortex," 10, 313-320. NOBLE, C. E. (1961) Measurement of association value (a) rated associations (a'), and scaled meaningfulness (m') for 2100 CVC combinations of the English alphabet, "Psycho!. Rep.," 8, 487-521. SATZ, P., ACHENBAH, K., and FENNELL, E. (1967) Correlations between manual laterality and predicted speech laterality in a normal population, "Neuropsychologia," 5, 295-310. VARNEY, N., and BENTON, A. L. (1975) Tactile perception of direction in relation to handedness and familial hendedness, "Neuropsychologia," 13 (in press). ZURIF, E. G., and BRYDEN, M. P. (1969) Familial handedness and left-right differences in auditory and visual perception, "Neuropsychologia," 7, 179-188.
Dr. H. J. Hannay and Mr. D. R. Malone, Department of Psychology, Auburn University, Auburn, AL 36830 U.S.A.
H. Julia Hannay and Daniel R. Malone (Department of Psychology, Auburn University)
Several studies support the concept of less complete lateralization of linguistic abilities in the left hemisphere and spatial abilities in the right hemisphere of females. For instances, with neurological patients, Lansdell (1961) found that left temporal lobe surgery disrupted only the performance of males on the Gorham's Proverbs Test. Analogously, Lansdell (1962) reported that right hemisphere lesions led to a drop in scores for males but not for females on the Graves Design Judgement Test. McGlone and Kertesz (1974) also found that right hemisphere damage resulted in negligibly lower scores for females on the Block Design subtest of the Wechsler Adult Intelligence Scale but significantly lower scores for males. Research findings with normal subjects are somewhat in accord. On a dot enumeration task, an equal number of females showed left and right visual field superiorities whereas a clear majority of males showed a left visual field superiority (McGlone and Davidson, 1973). Kimura (1969) reported a significant left visual field superiority for localization of a dot in a square or circular array by males. Females also obtained a significant left visual field superiority for dot localization with a circular array but a slight right visual field superiority with a square array. Hannay and Malone (1975) attempted to determine the relative contribution of reception and memory processes to the right visual field superiority for linguistic material generally obtained with normal right-handed males and females. Three letter nonsense words were presented unilaterally and vertically in the left and right visual fields for very short durations. Following memory intervals of 0, 5 or 10 sec., a duplicate of the test stimulus or a highly similar stimulus (differing by the middle letter) was presented in central vision and the subject stated whether this stimulus was the same as the test stimulus. Males showed a slight though non-significant left visual I This investigation was supported by Research Grant-In-Aid 74-79 awarded to the senior author by Auburn University.
Cortex (1976) 12, 41-48.
42
H.
J.
Hannay and D. R. Malone
field superIorIty with the 0 sec. memory interval indicating hemispheric equality in reception of linguistic material. Clear right visual field superiorities with the 5 and 10 sec. memory intervals supported greater left hemisphere involvement in retention of verbal material. Furthermore, an optimal interval for retention of verbal material was suggested since the right visual field superiority was greatest with the 5-sec. interval, decreasing as the interval was increased to 10 sec. Females obtained non-significant right visual field superiorities with the 0 and 10 sec. memory intervals and a non-significant left visual field superiority with the 5 sec. interval. A possible interpretation of these findings is that in females the left and right hemispheres are not particularly specialized for reception or memory of linguistic material. But, on the basis of the memory function obtained with males, right visual field superiorities, though smaller, would be predicted for females with all intervals, the 5 sec. memory interval producing the greatest field difference. Satz, Achenbach and Fennell (1967) have found that 33% of righthanders obtaining a right ear superiority on a dichotic listening task reported left-handed family members while 56% of right-handers obtaining a left ear superiority reported left-handed family members. Similarly, Zurif and Bryden (1969) and Hecaen and Sauguet (1971) have demonstrated that familial handedness is a determinant of hemispheric asymmetry of function in lefthanders. Information concerning the handedness of parents and siblings participating in the study by Hannay and Malone (1975) was available since subjects had filled out the Neurosensory Center Handedness Questionnaire (Benton, Meyers and Polder, 1962). Examination of these records revealed that all of the male subjects were familial right-handers; that is, their parents and siblings were also right-handed. However, one third of the female subjects were nonfamilial right-handers having at least one left-handed parent or sibling. It seems reasonable, then, to suggest that left-handedness in the immediate family of some of the females might have contributed to the rather unusual field effects for that group. Consideration of the studies in which sex or familial handedness were variables leads to specific predictions concerning the performance of righthanded females on laterality tasks involving linguistic material: (1) Familial right-handed females should exhibit right visual field superiorities similar to those reported for males. The laterality effects should, however, be smaller. (2) Non-familial right-handed females should exhibit visual field superiorities of similar magnitude to those obtained by familial right-handed females, in the left rather than the right visual field. The present study was designed to investigate these predictions with the stimuli previously employed by Hannay and Malone (1975).
Visual field recognition memory
43
MATERIALS AND METHOD
Subjects
Thirty right-handed female undergraduates, aged 18-29 years and enrolled in psychology courses at Auburn University, volunteered for the study. A modification of the handedness questionnaire used by Benton, Meyers and Polder (1962) was used to determine handedness of the subject and familial handedness. Twenty-seven of the subjects classified themselves as strongly right-handed and three as moderately right-handed though all reported use .of the right hand for at least 8 of 10 hand activities. Fifteen females with only right-handed parents and siblings formed the familial right-handed group. Fifteen females with a lefthanded parent or sibling formed the non-familial right-handed group. A Bausch and Lomb Modified Orthorater was used to determine visual characteristics. All subjects demonstrated 20/25 or better acuity in each eye and both eyes together, normal vertical phoria and normal lateral phoria, all at both near and far distances. Stimuli
Twenty-four three letter nonsense words were selected from the CVC list of Noble (1961). The four pretest stimuli and their respective incorrect foils had a mean association value of 2.10 (S.D. = .054). The eight test stimuli and their respective incorrect foils had a mean rated association value of 2.06 (S.D. = .049). Test stimuli and their incorrect foils differed by the middle letter. Prestype dry transfer lettering (Helvetica 1320 - 24 CLN) was used to print black letters vertically on white stimulus cards. The words subtended a visual angle of about 1° 40' vertically. Pretest stimuli were centered on the cards. Test stimuli appeared 2° either to the left or right of a central fixation point. Apparatus
A Gerbrands 4-field tachistoscope model T-4A with an automatic card changer and three semiautomatic card backs was employed. The stimuli were illuminated in one field. The second field contained a small black circle and the third field, a small black dot, both centrally located. The fourth field contained a blank white card. The fields were aligned and maintained at a luminance of approximately 20 cd/m2 • Procedure
The experiment consisted of two parts: a pretest task to obtain the stimulus exposure duration for each subject and a test task to determine the visual field effects for the nonsense words. At the beginning of every trial, the subject fixated on a small black circle in the center of a lighted screen. The black circle was replaced by a small black dot which served as a warning signal. Two seconds later the dot disappeared and a stimulus was presented. During the pretest task, the nonsense words appeared in central vision. The subject immediately looked away from the viewer and stated whether the nonsense word on a card displayed by the experimenter was the same as (or differed from) the previously presented word. In a trial block, each of the four stimuli was presented twice, followed once by a correct foil (the stimulus) and followed once by an incorrect foil. The pretest task consisted of 5 blocks of 8 trials. The stimulus duration was
44
H. ]. Hannay and D. R. Malone
varied over trial blocks according to the rules of Block Up and Down, TwoInterval Forced-Choice procedure (Campbell, 1963) as modified by Hannay (1972). The first trial block constituted practice judgments and the responses were discarded. A straight line relating the proportion of correct responses for trial blocks to the stimulus duration was fitted to the data of the last four trial blocks by visual inspection and the duration expected to produce .75 proportion of correct responses was determined. For the test task nonsense words were presented in the left or right visual field at the previously computed duration and a memory interval intervened between stimulus and response. Following a sec. memory interval the subject immediately looked away from the viewer to a foil displayed by the experimenter, stating whether the nonsense word was the same as the previously presented stimulus. With 5 and 10 sec. memory intervals, the subject continued to look at a blank, white, lighted screen after stimulus presentation until the fixation circle reappeared at the end of the interval. Then the subject made the samedifferent response to a foil. The test task consisted of three blocks of 32 trials differing by the duration of the memory interval (0, 5 or 10 sec.). Within a trial block, each of the eight nonsense words was presented twice in the left and twice in the right visual field, followed by the correct and incorrect foils once. A different random order was prepared for each .block but the same random orders were used throughout the experiment. Three orders of presentation of the memory intervals were used (0, 10, 5; 5, 0, 10; 10, 5, 0). Each order was administered to 5 familial and 5 non-familial right-handed females .
°
RESULTS
The stimulus exposure duration ranged from 5-28 msec. for the familial right-handers (mean = 11 msec.) and from 7-15 msec. for the non-familial right-hander (mean = 11 msec.). The familial right-handers were correct on 76.9 % of the test trials. The non-familial right-handers were correct on 74.9% of the test trials. The procedure for obtaining the stimulus duration for each subject thus produced comparable performance for both groups. The dependent measure was the number of correct responses for each subject as a function of visual field and memory interval. An analysis of variance was completed in which visual field and memory interval were within subject factors. Familial handedness and order of presentation of memory intervals were between subject factors. More nonsense words were correctly recognized in the RVF than in the LVF (Table I) but the RVF superiority was non-significant (F = 1.36, df 1, 24). Interactions between the variables visual field, memory interval and familial handedness were all statistically non-significant. Determination of the statistical significance of visual field differences at each memory interval for both groups was the major concern of this study. Where the overall F test is non-significant, orthogonal planned comparisons are still justified (Lindmann, 1974). These planned comparisons were made using the appropriate errorterm (MS within fields) from the overall analysis
Visual field recognition memory TABLE
45
I
Mean Number of Correct Nonsense Word Recognitions in the Left and Right Visual Fields for Familial and Non-Familial Female Right-Handers as a Function of the Memory Interval
Memory interval (sec.)
LVF
RVF
(RVF-LVF)
LVF
RVF
0
12040
12.60
0.20
11.93
11.53
-0040
5
11.47
12.80
1.33*
11040
11.20
-0.20
10
12.20
12.33
0.13
11.67
12.67
1.00
XML
12.02
12.58
0.56
11.47
12.00
0.53
* p
Non-familial
Familial
(RVF-LVF)
< .05
in a one-tailed test of significance. The familial right-handers demonstrated a significant right visual field superiority with the 5 sec. memory interval (t = 1.901 df = 24, P < .05). A slight and non-significant right visual superiority was obtained with the 0 sec. memory interval (t = .297, df = 24) and the 10 sec. memory interval (t = .198, df = 24). The non-familial right-handers demonstrated a slight non-significant left visual superiority with the 0 sec. memory interval (t = .594, df = 24) and the 5 sec. memory interval (t = .297, df = 24). A non-significant right visual field superiority followed the 10 sec. memory interval (t = 1.486, df = 24). Figure 1 shows the visual field superiorities for both groups as a function of memory interval. Accuracy of recognition did not vary significantly with the duration of the memory interval (F = 1.04, df = 2, 48). The order of presentation of
1.5
- - Familial
+---+ Nonfamilial 1.0 u..
> -'
IX I
0.5
u..
>
""
IX
0
5
---------
-0.5
--+/
/
·----Memory Interval (sec.)
Fig. 1 - Differences in visual field recognition scores for females as a functions of memory interval and familial handedness.
46
H.
J. Hannay
and D. R. Malone
the memory intervals did not affect the visual field differences (F = 0.12, df = 2, 48). Ten of the familial right-handers and seven of the nonfamilial righthanders showed an overall right visual field superiority. Four of both the familial and non-familial right-handers demonstrated a greater accuracy of recognition in the left visual field. One of the familial right-handers and four of the non-familial right-handers showed no overall field differences.
DISCUSSION
The procedure was identical to that of Hannay and Malone (1975) with one exception. The pretest task consisted of five trial blocks rather than eight. The exposure duration determined with this task was expected to produce 75% correct responses when the stimuli were presented in the left and right visual fields. In the previous study performance levels were 715% and 73% correct responses for males and females respectively. Performance of the females in the present study was remarkably close to these values and suggests that the pretest procedure can be shortened with no loss of precision. In general, predictions concerning the performance of familial right-handed females were supported. Linguistic material was recognized more accurately in the right visual field. Reception of linguistic material appears to be accomplished equally well by both hemispheres as indicated by the nonsignificant field effect with the immediate response. The marginally significant right visual field superiority with the 5 sec. memory interval is indicative of more accurate retention of linguistic material by the left hemisphere, at lea.st over relatively short intervals. For familial right-handed males Hannay and Malone (1975) reported a highly significant right visual field superiority with the 5 sec. interval (p < .005) and a slightly significant right visual field superiority with the 10 sec. interval (p < .05). If linguistic functions are less completely lateralized in females, then familial right-handed females should exhibit similar but smaller right visual field superiorities, the largest field difference occurring with the 5 sec. interval. These are precisely the findings. Predictions concerning the performance of non-familial right-handed females were not upheld. Performance similar to that of the familial righthand~rs, with the superiorities in the left visual field, was expected. Instead, no significant visual field effects were obtained. Recently, Varney and Benton (1975) examined tactile perception of direction, a spatial function presumably subserved by the right hemisphere. The usual left hand superiority for right-handers was demonstrated by 74% of the familial right-handers, 67% of right-handers with a left-handed sibling,
Visual field recognition memory
47
and 40% of right-handers with a left-handed parent. It seems that hand preference of parents is a stronger determinant of performance on a tactile laterality task than handedness of siblings. This factor was not controlled in the present study. Clearly, familial handedness is an important variable. The unusual field effects reported for females in the previous study (Hannay and Malone, 1975) probably can be attributed to a lack of control over this variable in subject selection. Both sex and familial handedness must be considered in research on cerebral asymmetry of function. These factors and factors which are not yet identified probably influence performance on tachistoscopic tasks, dichotic listening tasks and tactile tasks in very complex ways. SUMMARY
Recognition memory for nonsense words presented vertically and unilaterally in the left and right visual fields was investigated in right-handed females as a function of the memory interval and familial handedness. The subject decided whether another nonsense word presented in central vision after memory intervals of 0, 5 or 10 sec. was the same as the stimulus word. The exposure duration producing a recognition accuracy of about 75% for each subject was employed and ranged from 5 to 28 msec. Right-handed females with only right-handed family members demonstrated right visual field superiorities indicative of a slight left hemisphere specialization for memory but not for reception of verbal material. Field superiorities obtained for right-handed females with a left-handed parent or sibling were not significant. In general, less complete lateralization of linguistic function in females was indicated and the importance of familial handedness in cerebral asymmetry of function was confirmed. Acknowledgements. The authors wish to thank Judith Rogers and Maria Puente-Duany for their invaluable assistance in assessing subjects and obtaining the data reported in this study. REFERENCES BENTON, A. L., MEYERS, R., and POLDER, G. (1962) Some aspects of handedness, "Psychiat. Neurol.," 144, 321-337. CAMPBELL, R. A. (1963) Detection of a noise signal of varying duration, "J. Acoust. Soc. Amer.," 35, 1732-1736. HANNAY, H. J. (1972) Age and the time-intensity reciprocity relation for two temporally separated flashes of light, Ph. D. Dissertation, University of Iowa. - , and MALONE, D. R. (1976) Visual field effects and short-term memory for verbal material, "Neuropsychologia," (in press). HECAEN, H., and SAUGUET, J. (1971) Cerebral dominance in left-handed sub;ects, "Cortex," 7, 19-48. KIMURA, D. (1969) Spatial localization in the left and right visual field, "Can. J. Psychol.," 23, 445-458. LANSDELL, H. (1961) The effect of neurosurgery on a test of proverbs, "Amer. Psychol.," 16, 448. (1962) A sex differenc(! in effect of temporal-lobe neurosurgery on design preference, "Nature," 194, 852-854.
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H. f. Hannay and D. R. Malone
LINDMAN, H. R. (1974) Analysis of Variance in Complex Experimental Designs, Freeman, San Francisco. MCGLONE, ]., and DAVIDSON, W. (1973) The relation between cerebral speech laterality and spatial ability with special reference to sex and hand preference, "Neuropsychologia," 11, 105-113. and KERTESZ, A. (1974) Sex differences in cerebral processing of visuospatial tasks, "Cortex," 10, 313-320. NOBLE, C. E. (1961) Measurement of association value (a) rated associations (a'), and scaled meaningfulness (m') for 2100 CVC combinations of the English alphabet, "Psycho!. Rep.," 8, 487-521. SATZ, P., ACHENBAH, K., and FENNELL, E. (1967) Correlations between manual laterality and predicted speech laterality in a normal population, "Neuropsychologia," 5, 295-310. VARNEY, N., and BENTON, A. L. (1975) Tactile perception of direction in relation to handedness and familial hendedness, "Neuropsychologia," 13 (in press). ZURIF, E. G., and BRYDEN, M. P. (1969) Familial handedness and left-right differences in auditory and visual perception, "Neuropsychologia," 7, 179-188.
Dr. H. J. Hannay and Mr. D. R. Malone, Department of Psychology, Auburn University, Auburn, AL 36830 U.S.A.