Perceptual and Motor Skills, 1975, 40, 387-391. @ Perceprual and Motor Skills 1975
HUMAN SEX DIFFERENCES IN EXTREME ISOLATION1 G A R Y MC CLURE Long Island University
AND
DONALD G. FORGAYS Univerrity of Vermont
Summary.-This report compares the responses of male and female adult subjects i n the water-immersion sensory-isolation environment. Endurance, subjective time estimates, and heart rate were dependent variables. Duration under water, with voluntary termination possible, was an average of about 4 hr. for both males and females. Subjective estimate of total time in isolation averaged about 3Y2 hr. for females and almost 4 hr. for males. Subjective time estimate of consecutive 30-min. time intervals was a bit more than 30 min. for males and about 33 min. for females. Mean heart rate (beats/minute) averaged i n the 80s for both groups. None of these differences is statistically significant. This study clarifies the mixed findings reported in the literarure as to sex differences in isolated environments.
The effects of sensory deprivation or isolation on males and females have been referenced for a number of years, but the findings have been quite mixed as to the reliability of sex differences. In nine of these studies the quiet room is employed to produce perceptual or sensory deprivation, while in three studies the under-water immersion technique is used. In an early room study, Smith and Lewty (1959) investigated the duration of stay, with voluntary rerrnination, of 9 males and 11 females and found the females stayed an average of 49 hr. while the males only stayed an average of 29 hr. Since these male subjects appeared to be more neurotic than the females on the Maudsley Medical Questionnaire Neuroticism scores, Myers (1969) covaried duration in isolation with the Maudsley scores and the sex difference in duracion disappeared. In contrast to the Smith and Lewty (1959) uncorrected duration finding, Pollard, Uhr, and Jackson (1963) r e p r c that in a two run perceptual deprivation design, twelve male undergraduate subjects stayed in isolation for an average of about 7 and 8 hours while twelve female undergraduate subjeccs remained for about 5Y2 hours on each run. There were no emotionality differences between these two groups as measured by interview and MMPI scores. Perhaps some support for the position of male endurance is provided by Davis, McCourt, Courtney, and Solomon (1961) who found that fewer pairs of male strangers quit perceptual deprivation earlier than pairs of married couples, although there are many reasons why this result might have obtained. With respect to sex differences in response t o isolation on variables ocher than duration, male subjeccs may be more prone to hallucinations than females 'This study was carried our at the Isolation and Biorhythms Laboratory, Deparment of Psychology, John Dewey Hall, University of Vermont. It was supported in whole by AFOSR Contract F44620-69-C. The authors wish to thank Patrice C. Haring - for her statistical and clerical assistance.
388
G.MC CLURE & D. G. FORGAYS
(Zubek, Pushkar, Sansom, & Gowing, 1961) and may show a greater decrease in GSR and report more visual sensations of a structured type than females, while females show significantly higher stress on a post-isolation interview than males (Biase & Zuckerman, 1967). Additional affective sex differences are reported by Zuckerman, Persky, Link, and Basu (1968). On the other hand, no sex differences as a function of isolacion were found in reports of imagery, GSR, or heart rate by Leiderman (1962), or on time estimation, disturbance of imagery, or reported general disturbances on a postquestionnaire, as reported by Arnhoff and Leon (1963), or on reported body movement or disturbance of body orientation or body image (Reed & Kenna, 1964), or on spontaneous reports during isolation, on behavioral tests and selfratings after isolation, or on reporred visual or auditory sensations (Pollard, Uhr, & Jackson, 1963). In the under-water immersion studies, Francis (1964) reports no sex differences on duracion of stay on the basis of 12 female and 12 male subjects and a maximum of a 3-hr. stay under water. Walters, Shurley, and Parsons (1962) and Walters, Parsons, and Shurley (1964) reporr thac in a 3-hr. under-water design, male subjects are more stimulus bound than female subjects in that they are more concerned with water temperature, body comfort, and the like, while female subjects daydream and report hallucinatory phenomena more, in contrast with the Zubek, et al. (1961) finding on male's proneness to hallucinatory activity. Several of these auchors suggest that females more willingly than males indicate discomfort in the isolacion situation and that males more than females see the situation as one in which they must prove themselves as adequate. It is clear from the above thac the sex differences in isolation research are by no means consistent across studies, especially with respect to durational effects. It is equally clear that further study of the issue must be undertaken for clarification of effect, since there has been an ever increasing need for the efficient functioning of personnel of both sexes in extremely reduced sensory environments such as those encountered in space and ocean exploration. Additionally, as Zuckerman has pointed out ( 1969), physiological measures should definitely be added to such experimental designs. The present study compares the responses of males and females in an extreme isolation environment. Endurance, subjective time estimations and heart rate are the dependent variables. This is the first study to report physiological data relative to sex differences in wacer-immersed isolacion.
METHOD Subjects
Subjects, 14 males and 10 females, between 20 and 31 yr. of age, were enrolled in educational programs at the University of Vermont. Participation
SEX DIFFERENCES IN EXTREME ISOLATION
389
in the experiment was contingent only upon passing a routine physical examination and demonstrating a clear alpha rhythm and alpha blocking during an EEG pre-screening. Each subject was paid a $50.00 honorarium for participation.
Apparatus The isolation environment was a wooden tank 9 ft. in diameter and 7 ft. high filled with wacer at approximately skin temperature ( 9 4 ' ) . A parachute harness positioned the subject and suspended him vertically upright in the center of the tank. A shallow-water diving helmet provided the subject continuously with compressor-supplied air. Visual stimulation was eliminated and auditory stimulation minimized by blacking out the helmet and installing a head-set in it. The apparatus was adjusted until the subject felt comfortable and relatively weightless. Electrodes were attached to the subject and connected to a polygraph in an adjoining room to provide a continuous record of heart rate (EKG) throughout the run. A signal switch was taped to the subject's preferred hand to be used to signal subjective 30-rnin. time estimations.
Procedzlre The subject was told that total isolation would not exceed 24 hr. The experimenters, however, were prepared to terminate the subject after 12 hr. if he/she had not already terminated himself/herself. The subject could terminate the run at any time by voice communication or by holding open the time estimation switch continuously. The experimenters were in voice communication with subject until he/she was situated comfortably in the tank. When the run was started no further voice contact was permitted until termination of the session. At thac time, the subject was asked to estimate the total amount of time spent under water. Additionally, as described above, the subject estimated the passage of each successive 30 rnin. of time under wacer by closing the time switch briefly, thereby ringing a bell in the experimenter's room. The polygraph record of heart rate was analyzed by taking a random minute of record within each 5-min. period of the run and counting the heart beats for thac minute. These counts were then averaged for the entire run for each subject.
RESULTS Duration under wacer, subjective estimate of total time under water, subjective time estimates of 30-min. passages, and heart rate over the entire run for the two groups are given in Table 1. Both means and standard deviations are provided there. As can be seen, duration under water was an average of slightly over 4 hr. for the male subjects and slightly under 4 hr. for the females. Subjective estimate of time under water averaged about 3Y2 hr. for females and al-
G. MC CLURE & D. G. FORGAYS TABLE 1 MEANSAND STANDARD DEVIATIONS FOR VARIOUS MEASURES TAKENON TWO GROUPS OF SUBJECTS 14 Male Subjects M SD
Objective time in tank (min.) Subjective time in tank (min.)
244.64 232.64 Subjective rime estimates of 30 min. 30.46 Heart rate (beats/minute) 81.07
104.20 89.12 13.18 8.36
10 Female Subjects
M
SD
236.50 215.00 33.27 86.37
83.79 70.43 12.08 5.71
most 4 hr. for males. Subjective time estimates of 30 min. passing were 30.46 for the males and 33.27 for the females. Mean heart rate averaged in the 80s for the two groups. None of these differences is statistically significant.
DISCUSSION It should be emphasized that the data shown in Table 1 not only do not achieve statistical significance between the two groups of subjects, but are very similar for the male and female subjects. This is so for both the behavioral measures of duration under water and subjective time estimates as well as the physiological index of heart rate. The duration finding here of no sex differences is in agreement with that of Francis (1964) in a similar water environment but not with those of Pollard, Uhr, and Jackson (1963) in a quiet room environment. Five of the present 14 male subjects and five of the present 10 female subjects also spent time in a quiet room in our laboratory and there was no difference in endurance between the two groups. Perhaps the differences between our results and those of Pollard, et al. are due to instructional differences, differences in subjects' expectancies, and the like. Certainly many of the sex differences reported in sensory-deprivation studies, especially those based on verbal indicants of stress or discomfort, appear to be related to sex differences in expectancy sets, as Zuckerman (1969) has already pointed out. When physiological indices are obtained in sensory-deprivation studies, sex differences are not found. Using a quiet room Biase and Zuckerman (1967) report no sex differences in GSR; Leiderman (1962) reports no sex differences in GSR or heart rate. The present study extends findings of no sex differences in heart rate to the water-immersion isolation environment. There are indications that water-immersion stimulates a more stressful response in the typical subject than the quiet room. If this is so, it is possible that the greater stress under water mitigates the influence of sets or expectancies which may have an important effect in a less stressful environment, such as the quiet room. Additional studies would have to be undertaken to rest this possibility.
SEX DIFFERENCES I N EXTREME ISOLATION REFERENCES
ARNHOFF,F. N., & LEON, H. V. Sex differences in res nse to short-term sensory , 81-82. deprivation and isolation. Perceptual and Moros ~ k i l g 1 9 6 3 17, BIASE, D. V., & ZUCKERMAN, M. Sex differences in stress responses to total and partial sensory deprivation. P~ychosomaticMedicine, 1967, 29, 380-390. DAVIS, J. M., MCCOURT,W. F., COURTNEY,J., & SOLOMON,P. Sensory deprivation, the role of social isolation. Archives of General Psychiatry, 1961, 5 , 84-90. FRANCIS,R. D. The effect of prior instructions and time knowledge on the toleration of sensory isolation. Journal o f Nervous aad Mental Disease, 1964, 139, 182-185. LEIDERMAN,P. H. Imagery and sensory deprivation, an experimental study. Technical Report MRL-TDR62-28, Wright-Patterson Air Force Base, Ohio, May, 1962. MYERS, T. I. Tolerance for sensory and perceptual deprivation. In J. P. Zubek (Ed.), Sensory deprivation: fifteen years of research. New York: Appleton-CenruryCrofts, 1969. Pp. 289-331. POLLARD, J. C., UHR, L., & JACKSON,C. W., JR. Studies in sensory deprivation. A~chiver of General Psychiatry, 1963, 8 , 435-454. REED, G. F., & KENNA, J . C. Sex differences in body imagery and orientation under sensory deprivation of brief duration. Perceptual and Motor Shills, 1964, 18, 117-118. SMITH, S., & LEWN, W. Perceptual isolation using a silent room. Lancet, 1959, 2, 342-345. WALTERS,C., PARSONS,0. A,, & SHURLEY, J. T. Male-female differences in underwater sensory isolation. British Journal of Psychiatry, 1964, 110, 290-295. WALTERS,C., SHURLEY,J. T., & PARSONS,0.A. Differences in male and female responses to underwater sensory deprivation: an exploratory study. lousml o f Nervous and Mental Disease, 1962, 135, 302-310. ZUBEK,J. P., PUSHKAR,D., SANSOM,W., & GOWING,J. Perceptual changes after longed sensory isolation (darkness and silence). Canddian Journd o f ~ s y c b o ~ ~ ; 1961, 15, 83-100. ZUCKERMAN,M. Variables affecting deprivation results. In J. P. Zubeck (Ed.), Sensory deprivation: fifteen years of research. New York: Appleton-Century-Crofts, 1969. Pp. 47-84. ZUCKERMAN,M., PERSKY,H., LINK, K. E., & BASU, G. K. Experimental and subject factors determining responses to sensory deprivation, social isolation, and confinemenc. Journal of Abnormal Psychology, 1968, 73, 183-194. Accepted Decembw 9, 1974.
HUMAN SEX DIFFERENCES IN EXTREME ISOLATION1 G A R Y MC CLURE Long Island University
AND
DONALD G. FORGAYS Univerrity of Vermont
Summary.-This report compares the responses of male and female adult subjects i n the water-immersion sensory-isolation environment. Endurance, subjective time estimates, and heart rate were dependent variables. Duration under water, with voluntary termination possible, was an average of about 4 hr. for both males and females. Subjective estimate of total time in isolation averaged about 3Y2 hr. for females and almost 4 hr. for males. Subjective time estimate of consecutive 30-min. time intervals was a bit more than 30 min. for males and about 33 min. for females. Mean heart rate (beats/minute) averaged i n the 80s for both groups. None of these differences is statistically significant. This study clarifies the mixed findings reported in the literarure as to sex differences in isolated environments.
The effects of sensory deprivation or isolation on males and females have been referenced for a number of years, but the findings have been quite mixed as to the reliability of sex differences. In nine of these studies the quiet room is employed to produce perceptual or sensory deprivation, while in three studies the under-water immersion technique is used. In an early room study, Smith and Lewty (1959) investigated the duration of stay, with voluntary rerrnination, of 9 males and 11 females and found the females stayed an average of 49 hr. while the males only stayed an average of 29 hr. Since these male subjects appeared to be more neurotic than the females on the Maudsley Medical Questionnaire Neuroticism scores, Myers (1969) covaried duration in isolation with the Maudsley scores and the sex difference in duracion disappeared. In contrast to the Smith and Lewty (1959) uncorrected duration finding, Pollard, Uhr, and Jackson (1963) r e p r c that in a two run perceptual deprivation design, twelve male undergraduate subjects stayed in isolation for an average of about 7 and 8 hours while twelve female undergraduate subjeccs remained for about 5Y2 hours on each run. There were no emotionality differences between these two groups as measured by interview and MMPI scores. Perhaps some support for the position of male endurance is provided by Davis, McCourt, Courtney, and Solomon (1961) who found that fewer pairs of male strangers quit perceptual deprivation earlier than pairs of married couples, although there are many reasons why this result might have obtained. With respect to sex differences in response t o isolation on variables ocher than duration, male subjeccs may be more prone to hallucinations than females 'This study was carried our at the Isolation and Biorhythms Laboratory, Deparment of Psychology, John Dewey Hall, University of Vermont. It was supported in whole by AFOSR Contract F44620-69-C. The authors wish to thank Patrice C. Haring - for her statistical and clerical assistance.
388
G.MC CLURE & D. G. FORGAYS
(Zubek, Pushkar, Sansom, & Gowing, 1961) and may show a greater decrease in GSR and report more visual sensations of a structured type than females, while females show significantly higher stress on a post-isolation interview than males (Biase & Zuckerman, 1967). Additional affective sex differences are reported by Zuckerman, Persky, Link, and Basu (1968). On the other hand, no sex differences as a function of isolacion were found in reports of imagery, GSR, or heart rate by Leiderman (1962), or on time estimation, disturbance of imagery, or reported general disturbances on a postquestionnaire, as reported by Arnhoff and Leon (1963), or on reported body movement or disturbance of body orientation or body image (Reed & Kenna, 1964), or on spontaneous reports during isolation, on behavioral tests and selfratings after isolation, or on reporred visual or auditory sensations (Pollard, Uhr, & Jackson, 1963). In the under-water immersion studies, Francis (1964) reports no sex differences on duracion of stay on the basis of 12 female and 12 male subjects and a maximum of a 3-hr. stay under water. Walters, Shurley, and Parsons (1962) and Walters, Parsons, and Shurley (1964) reporr thac in a 3-hr. under-water design, male subjects are more stimulus bound than female subjects in that they are more concerned with water temperature, body comfort, and the like, while female subjects daydream and report hallucinatory phenomena more, in contrast with the Zubek, et al. (1961) finding on male's proneness to hallucinatory activity. Several of these auchors suggest that females more willingly than males indicate discomfort in the isolacion situation and that males more than females see the situation as one in which they must prove themselves as adequate. It is clear from the above thac the sex differences in isolation research are by no means consistent across studies, especially with respect to durational effects. It is equally clear that further study of the issue must be undertaken for clarification of effect, since there has been an ever increasing need for the efficient functioning of personnel of both sexes in extremely reduced sensory environments such as those encountered in space and ocean exploration. Additionally, as Zuckerman has pointed out ( 1969), physiological measures should definitely be added to such experimental designs. The present study compares the responses of males and females in an extreme isolation environment. Endurance, subjective time estimations and heart rate are the dependent variables. This is the first study to report physiological data relative to sex differences in wacer-immersed isolacion.
METHOD Subjects
Subjects, 14 males and 10 females, between 20 and 31 yr. of age, were enrolled in educational programs at the University of Vermont. Participation
SEX DIFFERENCES IN EXTREME ISOLATION
389
in the experiment was contingent only upon passing a routine physical examination and demonstrating a clear alpha rhythm and alpha blocking during an EEG pre-screening. Each subject was paid a $50.00 honorarium for participation.
Apparatus The isolation environment was a wooden tank 9 ft. in diameter and 7 ft. high filled with wacer at approximately skin temperature ( 9 4 ' ) . A parachute harness positioned the subject and suspended him vertically upright in the center of the tank. A shallow-water diving helmet provided the subject continuously with compressor-supplied air. Visual stimulation was eliminated and auditory stimulation minimized by blacking out the helmet and installing a head-set in it. The apparatus was adjusted until the subject felt comfortable and relatively weightless. Electrodes were attached to the subject and connected to a polygraph in an adjoining room to provide a continuous record of heart rate (EKG) throughout the run. A signal switch was taped to the subject's preferred hand to be used to signal subjective 30-rnin. time estimations.
Procedzlre The subject was told that total isolation would not exceed 24 hr. The experimenters, however, were prepared to terminate the subject after 12 hr. if he/she had not already terminated himself/herself. The subject could terminate the run at any time by voice communication or by holding open the time estimation switch continuously. The experimenters were in voice communication with subject until he/she was situated comfortably in the tank. When the run was started no further voice contact was permitted until termination of the session. At thac time, the subject was asked to estimate the total amount of time spent under water. Additionally, as described above, the subject estimated the passage of each successive 30 rnin. of time under wacer by closing the time switch briefly, thereby ringing a bell in the experimenter's room. The polygraph record of heart rate was analyzed by taking a random minute of record within each 5-min. period of the run and counting the heart beats for thac minute. These counts were then averaged for the entire run for each subject.
RESULTS Duration under wacer, subjective estimate of total time under water, subjective time estimates of 30-min. passages, and heart rate over the entire run for the two groups are given in Table 1. Both means and standard deviations are provided there. As can be seen, duration under water was an average of slightly over 4 hr. for the male subjects and slightly under 4 hr. for the females. Subjective estimate of time under water averaged about 3Y2 hr. for females and al-
G. MC CLURE & D. G. FORGAYS TABLE 1 MEANSAND STANDARD DEVIATIONS FOR VARIOUS MEASURES TAKENON TWO GROUPS OF SUBJECTS 14 Male Subjects M SD
Objective time in tank (min.) Subjective time in tank (min.)
244.64 232.64 Subjective rime estimates of 30 min. 30.46 Heart rate (beats/minute) 81.07
104.20 89.12 13.18 8.36
10 Female Subjects
M
SD
236.50 215.00 33.27 86.37
83.79 70.43 12.08 5.71
most 4 hr. for males. Subjective time estimates of 30 min. passing were 30.46 for the males and 33.27 for the females. Mean heart rate averaged in the 80s for the two groups. None of these differences is statistically significant.
DISCUSSION It should be emphasized that the data shown in Table 1 not only do not achieve statistical significance between the two groups of subjects, but are very similar for the male and female subjects. This is so for both the behavioral measures of duration under water and subjective time estimates as well as the physiological index of heart rate. The duration finding here of no sex differences is in agreement with that of Francis (1964) in a similar water environment but not with those of Pollard, Uhr, and Jackson (1963) in a quiet room environment. Five of the present 14 male subjects and five of the present 10 female subjects also spent time in a quiet room in our laboratory and there was no difference in endurance between the two groups. Perhaps the differences between our results and those of Pollard, et al. are due to instructional differences, differences in subjects' expectancies, and the like. Certainly many of the sex differences reported in sensory-deprivation studies, especially those based on verbal indicants of stress or discomfort, appear to be related to sex differences in expectancy sets, as Zuckerman (1969) has already pointed out. When physiological indices are obtained in sensory-deprivation studies, sex differences are not found. Using a quiet room Biase and Zuckerman (1967) report no sex differences in GSR; Leiderman (1962) reports no sex differences in GSR or heart rate. The present study extends findings of no sex differences in heart rate to the water-immersion isolation environment. There are indications that water-immersion stimulates a more stressful response in the typical subject than the quiet room. If this is so, it is possible that the greater stress under water mitigates the influence of sets or expectancies which may have an important effect in a less stressful environment, such as the quiet room. Additional studies would have to be undertaken to rest this possibility.
SEX DIFFERENCES I N EXTREME ISOLATION REFERENCES
ARNHOFF,F. N., & LEON, H. V. Sex differences in res nse to short-term sensory , 81-82. deprivation and isolation. Perceptual and Moros ~ k i l g 1 9 6 3 17, BIASE, D. V., & ZUCKERMAN, M. Sex differences in stress responses to total and partial sensory deprivation. P~ychosomaticMedicine, 1967, 29, 380-390. DAVIS, J. M., MCCOURT,W. F., COURTNEY,J., & SOLOMON,P. Sensory deprivation, the role of social isolation. Archives of General Psychiatry, 1961, 5 , 84-90. FRANCIS,R. D. The effect of prior instructions and time knowledge on the toleration of sensory isolation. Journal o f Nervous aad Mental Disease, 1964, 139, 182-185. LEIDERMAN,P. H. Imagery and sensory deprivation, an experimental study. Technical Report MRL-TDR62-28, Wright-Patterson Air Force Base, Ohio, May, 1962. MYERS, T. I. Tolerance for sensory and perceptual deprivation. In J. P. Zubek (Ed.), Sensory deprivation: fifteen years of research. New York: Appleton-CenruryCrofts, 1969. Pp. 289-331. POLLARD, J. C., UHR, L., & JACKSON,C. W., JR. Studies in sensory deprivation. A~chiver of General Psychiatry, 1963, 8 , 435-454. REED, G. F., & KENNA, J . C. Sex differences in body imagery and orientation under sensory deprivation of brief duration. Perceptual and Motor Shills, 1964, 18, 117-118. SMITH, S., & LEWN, W. Perceptual isolation using a silent room. Lancet, 1959, 2, 342-345. WALTERS,C., PARSONS,0. A,, & SHURLEY, J. T. Male-female differences in underwater sensory isolation. British Journal of Psychiatry, 1964, 110, 290-295. WALTERS,C., SHURLEY,J. T., & PARSONS,0.A. Differences in male and female responses to underwater sensory deprivation: an exploratory study. lousml o f Nervous and Mental Disease, 1962, 135, 302-310. ZUBEK,J. P., PUSHKAR,D., SANSOM,W., & GOWING,J. Perceptual changes after longed sensory isolation (darkness and silence). Canddian Journd o f ~ s y c b o ~ ~ ; 1961, 15, 83-100. ZUCKERMAN,M. Variables affecting deprivation results. In J. P. Zubeck (Ed.), Sensory deprivation: fifteen years of research. New York: Appleton-Century-Crofts, 1969. Pp. 47-84. ZUCKERMAN,M., PERSKY,H., LINK, K. E., & BASU, G. K. Experimental and subject factors determining responses to sensory deprivation, social isolation, and confinemenc. Journal of Abnormal Psychology, 1968, 73, 183-194. Accepted Decembw 9, 1974.
