EFFECT OF AUDITORY DEPRIVATION ON VISUAL RESOLVING POWER* MICHAEL BROSSt AND JOHN P. ZUBEK University of Manitoba ABSTRACT
Two experiments were conducted in which changes in the CFF were determined during and after auditory deprivation (silence). In Experiment i, subjects were exposed to one week of auditory deprivation, measurements of the CFF being taken at daily intervals and at Days 1, 2, 3, and 7 after the termination of the experimental condition. The results revealed that the experimental group exhibited a significant progressive improvement in visual resolving power as a function of auditory deprivation and, following its termination, a gradual decline towards the pre-experimental baseline. On the other hand, two control conditions, a group of confined subjects and a non-confined group showed no systematic changes in the CFF. In Experiment n the period of auditory deprivation was extended to 14 days. The results again revealed a progressive improvement on the CFF during the first week of silence followed by an asymptotic performance during the second week. The results are related to Schultz's (1965) sensoristatic theory which predicts intersensory enhancement effects as a function of sensory deprivation. DURING THE LAST DECADE, a series of studies conducted at this laboratory has demonstrated that a one-week period of visual deprivation (darkness) can produce significant intersensory enhancement effects on various measures of cutaneous, auditory, olfactory, and gustatory sensitivity, effects which persist for several days after the termination of visual deprivation (see Zubek, 1969 for review, pp. 236-40). As the measures in these experiments were restricted exclusively to the pre- and post-deprivation period, two further experiments were conducted in an attempt to ascertain the temporal course of development of these facilitatory cross modal effects. Milstein and Zubek (1971) reported that sensitivity on a tactual fusion task, a measure of temporal resolving power analogous to the critical flicker fusion ( C F F ) , showed a progressive improvement in performance as a function of duration of visual deprivation. Similar results were reported by Pangman and Zubek (1972) on an auditory flutter fusion task
•The research reported in this paper was supported by the National Research Council, Canada (Grant 311-1665-02) and the Defence Research Board (Grant 334-166502). The authors wish to express their appreciation to Messrs L. Bayer, D. Harper, R. Lundin, and W. Reid for their assistance in the running of the experiments. This article is based on a dissertation submitted by M. Bross in partial fulfilment of the requirement for the PHD degree. t Present address: Department of Psychology. Sir George Williams Faculty of Arts, Concordia University, Montreal, Quebec H3G 1M8. 340 CANAD. J. PSYCHOI../REV. CANAD. PSYCHOL. 1975, 29 (4)
1975]
AUDITORY DEPRIVATION
341
where again a progressive improvement in sensitivity was obtained as a function of duration of visual deprivation. It is of some interest to note, that the temporal course of development of these intersensory enhancement effects in both experiments was of a negatively accelerated nature and present in all subjects. The results of these studies are of theoretical importance since they provide experimental support for Schultz's (1965) sensoristatic model, a model that predicts the progressive lowering of sensory thresholds as a function of restriction in sensory stimulation. Although these studies have demonstrated that prolonged periods of visual deprivation can improve performance on a variety of non-visual tasks, no attention has been paid to the problem of whether similar facilitatory effects can result from auditory deprivation, a prediction that would follow from Schultz's sensoristatic theory. In order to test further the generality of the sensoristatic model, two experiments were conducted to determine whether auditory deprivation (silence) of up to 14 days duration can produce a significant improvement in visual performance as measured by the CFF. There are two main reasons for employing the CFF. First, it is a reliable measure of temporal visual acuity which is only minimally affected by practice and learning, Secondly, the measure is analogous to the previously employed tactual fusion and auditory flutter fusion task which have shown a progressive improvement in performance as a function of visual deprivation. The use of such an analogous task, therefore, makes it easier to ascertain whether a similar temporal pattern of CFF changes will occur during prolonged auditory deprivation. EXPERIMENT I
Method Apparatus: Acoustical Chamber. A double-unit soundproofed chamber consisting of a test room (2.64 m X 3.25 m X 2.44 m high) and an experimental room (3.05 m X 2.84 m X 1.98 m high) was employed (Model 1405-ACT, Industrial Acoustics corporation). Two such chambers were available. The test room used to measure the CFF was of single-wall construction, while the adjoining experimental room (the subject's living quarters) consisted of a room within a room separated by a 10 cm air space, the floor of the inner room being floated on rubber-in-shear vibration isolator rails to assure the maximum elimination of structurally borne sounds. Additional characteristics of the experimental room are two, 10 cm thick soundproofed doors, a silent ventilation system, and a sound reduction level of 81 db for frequencies > 600 c.p.s. Finally, the double wall separating the two rooms contains a large glazed window, a two-way intercom system, and a small food compartment closed at both ends by a soundproofed door. Subjects. The volunteers were 36 male university students who were randomly subdivided into an experimental, a confined control, and a non-confined control group, each containing 12 subjects. All subjects were paid for their participation in the study.
342
BROSS & ZUBEK
[Vol. 29, No. 4
The experimental subjects were required to live, individually, for a period of one week in the double-walled acoustical chamber which was furnished similar to a bedsitting room. It contained thick wall-to-wall carpeting, two comfortable cloth chairs, a desk covered with felt, a bed, a chemical toilet, and some brightly coloured pictures on the walls. The level of illumination in the room, produced by recessed lights in the ceiling, was 14 ft candles (150.7 I X ) , the measure being taken at desk height. The lights were extinguished between 11:30 P.M. and 8:00 A.M. by means of an automatic time clock located in the adjoining test room. The subjects were permitted to move about the room quietly (in slippers) and to engage in reading and writing activities. Furthermore, to reduce the level of any sounds produced by these and other activities, a pair of air-cushioned ear plugs (Willson "sound silencer," Model EP-100) were worn during their waking hours. Any necessary communication between the subject and experimenter was carried out via written message placed against the glass window or by placing them on a meal tray in the food compartment. A balanced diet on a fixed schedule was provided, and to minimize noise, plastic cutlery and paper cups and plates were used. Smoking was allowed at meal-times. No vocal activities such as singing or humming were permitted. (This was monitored by using an open-line intercom system terminating in a central control room.) At least one experimenter was on duty at all times to take care of any needs of the subject and to provide spot checks on his general behaviour. The purpose of die confined group was to control for the possible effect, on the CFF, of a prolonged period of solitary confinement in a relatively small chamber. These subjects were required to live for one week in a similarly furnished ordinary room of approximately the same dimensions as the acoustical chamber. Furthermore, they were exposed to essentially the same conditions as the experimental group. However, they wore no ear plugs, had access to both a radio and reading material, and were able to interact verbally with the experimenters on duty. The non-confined control group merely came to the laboratory at specified intervals during the one-week period, i.e., at the times corresponding to the test sessions of the other two groups. However, they were free to leave and engage in their normal daily activities in the intervening periods. Test Procedure. The CFF was taken at daily intervals during the one-week period, and subsequently, at intervals of 1, 2, 3, and 7 days after the termination of the experimental or control conditions. Each test session was preceded by 15 minutes of binocular dark adaptation and all measures were taken in the acoustical test room between 9:00 A.M. and 10:15 A.M., with each subject's testing time not varying by more than 5 minutes over successive days. The subjects were awake for at least one hour prior to the initiation of dark adaptation. The stimulus consisted of a white light, at an initial nicker frequency well above fusion (60 ± 5 c.p.s.), which was presented monocularly by a cold cathode modulating lamp (Sylvania, type R1131c), mounted at the rear of a standard viewing chamber (Lafayette, Model 1202C). The angle subtended by the centrally fixated stimulus was 2° 10', a value assuring full foveal stimulation. The flicker-generating apparatus (GrasonStadler, Model E622) was set at a light-dark ratio of 0.50 and a lamp current reading of 22.6 mA. The descending methods of limits was used, the flicker frequency being reduced in steps of one c.p.s. by means of a continuous variable control. Eight trials were presented to the dominant eye of one-half of the subjects and the non-dominant eye of the other half. (Eye dominance refers here to sighting dominance as determined by the widely used finger-pointing test.) The subjects' task was to report verbally the
1975]
AUDITORY DEPRIVATION
44.0 -
343
EXPERIMENTAL GROUP CONFINED CONTROLS NON-CONFINED CONTROLS
FIGURE 1. Changes in the CFF during and after a week of auditory deprivation and of two control conditions. first indication of flicker, the arithmetic mean of these eight trials being taken as the descending monocular CFF threshold. RESULTS
The results of Experiment i are summarized in Figure 1. It can be seen that the experimental subjects show a progressive improvement in CFF performance as a function of increasing duration of auditory deprivation and, following its termination, a graduate decline towards the pre-experimental baseline. On the other hand, both control groups show no systematic changes in the CFF during the entire 14-day test period. An analysis of variance (mixed design for repeated measures, Myers, 1966) performed on the overall data indicated a significant change over days, F( 11,363) = 9.62, p < .001, and a significant interaction effect, F( 22,363) = 12.76, p < .001. An examination of the individual performance of the 12 experimental subjects revealed that the effect of auditory deprivation was quite uniform. All 12 subjects showed an increased CFF at the end of the 7-day period, the individual gains ranging from .62 to 2.75 c.p.s. (mean gain = 1.78 cp.s.). Furthermore, this superior performance was already evident by the end of the first day of auditory deprivation - 9 of the 12 subjects showed an increased CFF, and ihe remainder, no change relative to Day 0. Finally, an examination of the post-deprivation results revealed that 9 of the 12 subjects still had not reached their individual baseline level 7 days
344
BROSS & ZUBEK
[Vol. 29, No. 4
FIGURE 2. Changes in the CFF during 14 days of auditory deprivation.
after the termination of the experimental condition, a finding which indicates that this visual phenomenon is of a long-lasting nature and may persist for a period equal to the auditory deprivation duration. EXPERIMENT n
The purpose of Experiment n, in which the duration of auditory deprivations extended to 14 days, was to determine whether the CFF performance would continue to improve during the second week or whether it would begin to decline towards the baseline level, an effect which might occur as a result of the subject's adaptation to the novelty of the experimental condition. Furthermore, since the same conditions were employed, this experiment also served as a replication of the first. Method Because of the consistency of the results which were obtained in Experiment i and the lengthy duration of the deprivation condition, only 6 experimental subjects were employed. Furthermore, no control groups were felt to be essential as neither of the two control conditions in the previous experiment had shown any systematic changes in the CFF over a 14-day period. Male university students were again used as subjects. The deprivation and testing procedures were identical with that of Experiment I, except that the subjects were exposed to a two-week rather than a one-week period of auditory deprivation and no follow-up measures were taken. RESULTS
Figure 2 summarizes the results of Experiment n. It can be seen that the experimental subjects show a progressive increase, of a negatively acceler-
1975]
AUDITORY DEPRIVATION
345
ated nature in the CFF during the first 8 days of auditory deprivation, thus replicating the results of Experiment i, followed by an essentially asymptotic level of performance from Day 8 to Day 14. Furthermore, a consistent pattern of improvement was observed, with all 6 subjects showing an increased CFF on Day 1 and individual gains ranging from 1.37 to 2.50 c.p.s. on Day 14 (mean again = 2.10 c.p.s.). DISCUSSION
This study represents the first attempt to determine whether intersensory facilitatory effects, similar to those resulting from visual deprivation, can be produced by a prolonged period of auditory deprivation or silence. This hypothesis was tested in two experiments and confirmed. The results of Experiment i demonstrated a progressive increase in the CFF as a function of increasing duration of auditory deprivation, a facilitatory effect that was shown by all of the experimental subjects. Further, since both the confined and the non-confined control subjects showed no systematic changes in CFF performance at any test period, it would appear that solitary confinement per se is not a variable in producing the superior visual performance in the experimental group. The results of this first study also revealed that this enhancement phenomenon is of a long-lasting nature, persisting for many days after the termination of the experimental condition. This temporal pattern of results, it is important to note, is similar in nature to that which has been reported in several visual deprivation studies employing sensory measures analogous to the CFF. Milstein and Zubek (1971) and Pangman and Zubek (1972) reported a progressive increase in tactual fusion frequency and auditory flutter fusion frequency during a week of visual deprivation. Furthermore, this superior performance was present in all subjects of both studies. In addition these visuallyproduced cutaneous and auditory enhancement effects were also found to be of a long-lasting nature (Duda & Zubek, 1965; Zubek, Flye, & Aftanas, 1964). It would appear, therefore, that when sensory measures of a temporal discriminatory nature are administered periodically during a week of either visual deprivation or auditory deprivation, a progressive improvement in performance will occur. The results of Experiment n, in which the duration of silence was extended to 14 days, again revealed a progressive improvement in visual performance during the first week, thus confirming the results of Experiment I. This was followed by an asymptotic or plateau-like performance during the remainder of the experimental period, a finding which suggests that an eventual dissipation or decrement in the magnitude of the phenomenon, through adaptation to the novelty of the environment, may not
346
BROSS & ZUBEK
[Vol. 29, No. 4
occur. This, however, is only a hypothesis; its confirmation must await future research. In the introduction reference was made to Schultz's (1965) theory of sensoristasis which predicts these intersensory, facilitatory effects. According to Schultz, sensoristasis is a drive condition, analogous to homeostasis in which the organism strives to maintain an optimal range of sensory stimulation, thus restriction of sensory input in one modality should lead to an increase in sensitivity in other modalities. The demonstration in this study that auditory deprivation can produce an improvement in visual performance, together with the earlier reports that visual deprivation can produce enhancement effects on a variety of non-visual sensory measures, provides substantial experimental support for the sensoristaric model. In addition, the sensoristatic theory also generates various testable hypotheses for future research. For example, it would predict that auditory deprivation should also increase cutaneous, olfactory, and gustatory sensitivity. Furthermore, since the theory states that the critical variable in producing cross modal sensory improvement is a reduction in stimulus variation, it would predict that not only silence but also constant white noise should produce these effects. Such findings would be consistent with the visual deprivation literature which has shown that both darkness (Zubek, Flye, & Aftanas, 1964) and diffuse homogeneous illumination (Zubek, Flye, & Willows, 1964) produce a significant increase in cutaneous sensitivity. RESUME Deux experiences sur les changements de la frequence critique de fusion ( CFF ) pendant et apres une privation auditive (silence). Dans la premiere, les sujets subissent une privation auditive d'une semaine, la CFF etant mesuree a chaque jour pendant la privation et aux jours 1, 2, 3 et 7 suivant la privation. Les resultats revelent, chez le groupe experimental, une amelioration progressive (significative) de la capacite de resolution visuelle a mesure que dure la privation et, apres la privation, un retour graduel vers le niveau de base. Par ailleurs, on n'observe aucun changement significatif chez deux groupes de contr61e (un groupe confine et un groupe non confine). Dans la seconde experience, la duree de la privation auditive atteint 14 jours. Les resultats relevent encore une amelioration progressive de la CFF pendant la premiere semaine de silence, la courbe devenant asymptotique pendant la seconde semaine. Ces resultats sont interpretes dans le contexte de la theorie sensoristatique de Schultz (1965) qui predit des effets mtersensoriels de renforcernent en fonction de la privation sensorielle. REFERENCES DODA, P., & ZUBEK, J.P. Auditory sensitivity after prolonged visual deprivation. Psychonom. Set., 1965, 3, 359-360.
1975]
AUDITORY DEPRIVATION
347
r, S.L., & ZUBEK, J.P. Temporal changes in cutaneous sensitivity during prolonged visual deprivation. Canad. J. Psychol, 1971, 25, 336-348. MYERS, J.L. Fundamentals of experimental design. Boston: Allyn & Bacon, 1966. PANGMAN, C.H., & ZUBEK, J.P. Changes in auditory flutter fusion frequency during prolonged visual deprivation. Percept. Psychophys., 1972, 11, 172-174. SCHULTZ, D.P. Sensory restriction: effects on behavior. New York: Academic Press, 1965. ZUBEK, J.P. (ed.) Sensory deprivation: fifteen years of research. New York: AppletonCentury-Crofts, 1969. ZUBEK, J.P., FLYE, J., & AFTANAS, M. Cutaneous sensitivity after prolonged visual deprivation. Science, 1964, 144,1591-1593. ZUBEK, J.P., FLYE, J., & WILLOWS, D.
Changes in cutaneous sensitivity after pro-
longed exposure to unpatterned light. Psychonom. Sci., 1964, 1, 283-284. (First received 6 March 1975) (Date accepted 15 August 1975)
Two experiments were conducted in which changes in the CFF were determined during and after auditory deprivation (silence). In Experiment i, subjects were exposed to one week of auditory deprivation, measurements of the CFF being taken at daily intervals and at Days 1, 2, 3, and 7 after the termination of the experimental condition. The results revealed that the experimental group exhibited a significant progressive improvement in visual resolving power as a function of auditory deprivation and, following its termination, a gradual decline towards the pre-experimental baseline. On the other hand, two control conditions, a group of confined subjects and a non-confined group showed no systematic changes in the CFF. In Experiment n the period of auditory deprivation was extended to 14 days. The results again revealed a progressive improvement on the CFF during the first week of silence followed by an asymptotic performance during the second week. The results are related to Schultz's (1965) sensoristatic theory which predicts intersensory enhancement effects as a function of sensory deprivation. DURING THE LAST DECADE, a series of studies conducted at this laboratory has demonstrated that a one-week period of visual deprivation (darkness) can produce significant intersensory enhancement effects on various measures of cutaneous, auditory, olfactory, and gustatory sensitivity, effects which persist for several days after the termination of visual deprivation (see Zubek, 1969 for review, pp. 236-40). As the measures in these experiments were restricted exclusively to the pre- and post-deprivation period, two further experiments were conducted in an attempt to ascertain the temporal course of development of these facilitatory cross modal effects. Milstein and Zubek (1971) reported that sensitivity on a tactual fusion task, a measure of temporal resolving power analogous to the critical flicker fusion ( C F F ) , showed a progressive improvement in performance as a function of duration of visual deprivation. Similar results were reported by Pangman and Zubek (1972) on an auditory flutter fusion task
•The research reported in this paper was supported by the National Research Council, Canada (Grant 311-1665-02) and the Defence Research Board (Grant 334-166502). The authors wish to express their appreciation to Messrs L. Bayer, D. Harper, R. Lundin, and W. Reid for their assistance in the running of the experiments. This article is based on a dissertation submitted by M. Bross in partial fulfilment of the requirement for the PHD degree. t Present address: Department of Psychology. Sir George Williams Faculty of Arts, Concordia University, Montreal, Quebec H3G 1M8. 340 CANAD. J. PSYCHOI../REV. CANAD. PSYCHOL. 1975, 29 (4)
1975]
AUDITORY DEPRIVATION
341
where again a progressive improvement in sensitivity was obtained as a function of duration of visual deprivation. It is of some interest to note, that the temporal course of development of these intersensory enhancement effects in both experiments was of a negatively accelerated nature and present in all subjects. The results of these studies are of theoretical importance since they provide experimental support for Schultz's (1965) sensoristatic model, a model that predicts the progressive lowering of sensory thresholds as a function of restriction in sensory stimulation. Although these studies have demonstrated that prolonged periods of visual deprivation can improve performance on a variety of non-visual tasks, no attention has been paid to the problem of whether similar facilitatory effects can result from auditory deprivation, a prediction that would follow from Schultz's sensoristatic theory. In order to test further the generality of the sensoristatic model, two experiments were conducted to determine whether auditory deprivation (silence) of up to 14 days duration can produce a significant improvement in visual performance as measured by the CFF. There are two main reasons for employing the CFF. First, it is a reliable measure of temporal visual acuity which is only minimally affected by practice and learning, Secondly, the measure is analogous to the previously employed tactual fusion and auditory flutter fusion task which have shown a progressive improvement in performance as a function of visual deprivation. The use of such an analogous task, therefore, makes it easier to ascertain whether a similar temporal pattern of CFF changes will occur during prolonged auditory deprivation. EXPERIMENT I
Method Apparatus: Acoustical Chamber. A double-unit soundproofed chamber consisting of a test room (2.64 m X 3.25 m X 2.44 m high) and an experimental room (3.05 m X 2.84 m X 1.98 m high) was employed (Model 1405-ACT, Industrial Acoustics corporation). Two such chambers were available. The test room used to measure the CFF was of single-wall construction, while the adjoining experimental room (the subject's living quarters) consisted of a room within a room separated by a 10 cm air space, the floor of the inner room being floated on rubber-in-shear vibration isolator rails to assure the maximum elimination of structurally borne sounds. Additional characteristics of the experimental room are two, 10 cm thick soundproofed doors, a silent ventilation system, and a sound reduction level of 81 db for frequencies > 600 c.p.s. Finally, the double wall separating the two rooms contains a large glazed window, a two-way intercom system, and a small food compartment closed at both ends by a soundproofed door. Subjects. The volunteers were 36 male university students who were randomly subdivided into an experimental, a confined control, and a non-confined control group, each containing 12 subjects. All subjects were paid for their participation in the study.
342
BROSS & ZUBEK
[Vol. 29, No. 4
The experimental subjects were required to live, individually, for a period of one week in the double-walled acoustical chamber which was furnished similar to a bedsitting room. It contained thick wall-to-wall carpeting, two comfortable cloth chairs, a desk covered with felt, a bed, a chemical toilet, and some brightly coloured pictures on the walls. The level of illumination in the room, produced by recessed lights in the ceiling, was 14 ft candles (150.7 I X ) , the measure being taken at desk height. The lights were extinguished between 11:30 P.M. and 8:00 A.M. by means of an automatic time clock located in the adjoining test room. The subjects were permitted to move about the room quietly (in slippers) and to engage in reading and writing activities. Furthermore, to reduce the level of any sounds produced by these and other activities, a pair of air-cushioned ear plugs (Willson "sound silencer," Model EP-100) were worn during their waking hours. Any necessary communication between the subject and experimenter was carried out via written message placed against the glass window or by placing them on a meal tray in the food compartment. A balanced diet on a fixed schedule was provided, and to minimize noise, plastic cutlery and paper cups and plates were used. Smoking was allowed at meal-times. No vocal activities such as singing or humming were permitted. (This was monitored by using an open-line intercom system terminating in a central control room.) At least one experimenter was on duty at all times to take care of any needs of the subject and to provide spot checks on his general behaviour. The purpose of die confined group was to control for the possible effect, on the CFF, of a prolonged period of solitary confinement in a relatively small chamber. These subjects were required to live for one week in a similarly furnished ordinary room of approximately the same dimensions as the acoustical chamber. Furthermore, they were exposed to essentially the same conditions as the experimental group. However, they wore no ear plugs, had access to both a radio and reading material, and were able to interact verbally with the experimenters on duty. The non-confined control group merely came to the laboratory at specified intervals during the one-week period, i.e., at the times corresponding to the test sessions of the other two groups. However, they were free to leave and engage in their normal daily activities in the intervening periods. Test Procedure. The CFF was taken at daily intervals during the one-week period, and subsequently, at intervals of 1, 2, 3, and 7 days after the termination of the experimental or control conditions. Each test session was preceded by 15 minutes of binocular dark adaptation and all measures were taken in the acoustical test room between 9:00 A.M. and 10:15 A.M., with each subject's testing time not varying by more than 5 minutes over successive days. The subjects were awake for at least one hour prior to the initiation of dark adaptation. The stimulus consisted of a white light, at an initial nicker frequency well above fusion (60 ± 5 c.p.s.), which was presented monocularly by a cold cathode modulating lamp (Sylvania, type R1131c), mounted at the rear of a standard viewing chamber (Lafayette, Model 1202C). The angle subtended by the centrally fixated stimulus was 2° 10', a value assuring full foveal stimulation. The flicker-generating apparatus (GrasonStadler, Model E622) was set at a light-dark ratio of 0.50 and a lamp current reading of 22.6 mA. The descending methods of limits was used, the flicker frequency being reduced in steps of one c.p.s. by means of a continuous variable control. Eight trials were presented to the dominant eye of one-half of the subjects and the non-dominant eye of the other half. (Eye dominance refers here to sighting dominance as determined by the widely used finger-pointing test.) The subjects' task was to report verbally the
1975]
AUDITORY DEPRIVATION
44.0 -
343
EXPERIMENTAL GROUP CONFINED CONTROLS NON-CONFINED CONTROLS
FIGURE 1. Changes in the CFF during and after a week of auditory deprivation and of two control conditions. first indication of flicker, the arithmetic mean of these eight trials being taken as the descending monocular CFF threshold. RESULTS
The results of Experiment i are summarized in Figure 1. It can be seen that the experimental subjects show a progressive improvement in CFF performance as a function of increasing duration of auditory deprivation and, following its termination, a graduate decline towards the pre-experimental baseline. On the other hand, both control groups show no systematic changes in the CFF during the entire 14-day test period. An analysis of variance (mixed design for repeated measures, Myers, 1966) performed on the overall data indicated a significant change over days, F( 11,363) = 9.62, p < .001, and a significant interaction effect, F( 22,363) = 12.76, p < .001. An examination of the individual performance of the 12 experimental subjects revealed that the effect of auditory deprivation was quite uniform. All 12 subjects showed an increased CFF at the end of the 7-day period, the individual gains ranging from .62 to 2.75 c.p.s. (mean gain = 1.78 cp.s.). Furthermore, this superior performance was already evident by the end of the first day of auditory deprivation - 9 of the 12 subjects showed an increased CFF, and ihe remainder, no change relative to Day 0. Finally, an examination of the post-deprivation results revealed that 9 of the 12 subjects still had not reached their individual baseline level 7 days
344
BROSS & ZUBEK
[Vol. 29, No. 4
FIGURE 2. Changes in the CFF during 14 days of auditory deprivation.
after the termination of the experimental condition, a finding which indicates that this visual phenomenon is of a long-lasting nature and may persist for a period equal to the auditory deprivation duration. EXPERIMENT n
The purpose of Experiment n, in which the duration of auditory deprivations extended to 14 days, was to determine whether the CFF performance would continue to improve during the second week or whether it would begin to decline towards the baseline level, an effect which might occur as a result of the subject's adaptation to the novelty of the experimental condition. Furthermore, since the same conditions were employed, this experiment also served as a replication of the first. Method Because of the consistency of the results which were obtained in Experiment i and the lengthy duration of the deprivation condition, only 6 experimental subjects were employed. Furthermore, no control groups were felt to be essential as neither of the two control conditions in the previous experiment had shown any systematic changes in the CFF over a 14-day period. Male university students were again used as subjects. The deprivation and testing procedures were identical with that of Experiment I, except that the subjects were exposed to a two-week rather than a one-week period of auditory deprivation and no follow-up measures were taken. RESULTS
Figure 2 summarizes the results of Experiment n. It can be seen that the experimental subjects show a progressive increase, of a negatively acceler-
1975]
AUDITORY DEPRIVATION
345
ated nature in the CFF during the first 8 days of auditory deprivation, thus replicating the results of Experiment i, followed by an essentially asymptotic level of performance from Day 8 to Day 14. Furthermore, a consistent pattern of improvement was observed, with all 6 subjects showing an increased CFF on Day 1 and individual gains ranging from 1.37 to 2.50 c.p.s. on Day 14 (mean again = 2.10 c.p.s.). DISCUSSION
This study represents the first attempt to determine whether intersensory facilitatory effects, similar to those resulting from visual deprivation, can be produced by a prolonged period of auditory deprivation or silence. This hypothesis was tested in two experiments and confirmed. The results of Experiment i demonstrated a progressive increase in the CFF as a function of increasing duration of auditory deprivation, a facilitatory effect that was shown by all of the experimental subjects. Further, since both the confined and the non-confined control subjects showed no systematic changes in CFF performance at any test period, it would appear that solitary confinement per se is not a variable in producing the superior visual performance in the experimental group. The results of this first study also revealed that this enhancement phenomenon is of a long-lasting nature, persisting for many days after the termination of the experimental condition. This temporal pattern of results, it is important to note, is similar in nature to that which has been reported in several visual deprivation studies employing sensory measures analogous to the CFF. Milstein and Zubek (1971) and Pangman and Zubek (1972) reported a progressive increase in tactual fusion frequency and auditory flutter fusion frequency during a week of visual deprivation. Furthermore, this superior performance was present in all subjects of both studies. In addition these visuallyproduced cutaneous and auditory enhancement effects were also found to be of a long-lasting nature (Duda & Zubek, 1965; Zubek, Flye, & Aftanas, 1964). It would appear, therefore, that when sensory measures of a temporal discriminatory nature are administered periodically during a week of either visual deprivation or auditory deprivation, a progressive improvement in performance will occur. The results of Experiment n, in which the duration of silence was extended to 14 days, again revealed a progressive improvement in visual performance during the first week, thus confirming the results of Experiment I. This was followed by an asymptotic or plateau-like performance during the remainder of the experimental period, a finding which suggests that an eventual dissipation or decrement in the magnitude of the phenomenon, through adaptation to the novelty of the environment, may not
346
BROSS & ZUBEK
[Vol. 29, No. 4
occur. This, however, is only a hypothesis; its confirmation must await future research. In the introduction reference was made to Schultz's (1965) theory of sensoristasis which predicts these intersensory, facilitatory effects. According to Schultz, sensoristasis is a drive condition, analogous to homeostasis in which the organism strives to maintain an optimal range of sensory stimulation, thus restriction of sensory input in one modality should lead to an increase in sensitivity in other modalities. The demonstration in this study that auditory deprivation can produce an improvement in visual performance, together with the earlier reports that visual deprivation can produce enhancement effects on a variety of non-visual sensory measures, provides substantial experimental support for the sensoristaric model. In addition, the sensoristatic theory also generates various testable hypotheses for future research. For example, it would predict that auditory deprivation should also increase cutaneous, olfactory, and gustatory sensitivity. Furthermore, since the theory states that the critical variable in producing cross modal sensory improvement is a reduction in stimulus variation, it would predict that not only silence but also constant white noise should produce these effects. Such findings would be consistent with the visual deprivation literature which has shown that both darkness (Zubek, Flye, & Aftanas, 1964) and diffuse homogeneous illumination (Zubek, Flye, & Willows, 1964) produce a significant increase in cutaneous sensitivity. RESUME Deux experiences sur les changements de la frequence critique de fusion ( CFF ) pendant et apres une privation auditive (silence). Dans la premiere, les sujets subissent une privation auditive d'une semaine, la CFF etant mesuree a chaque jour pendant la privation et aux jours 1, 2, 3 et 7 suivant la privation. Les resultats revelent, chez le groupe experimental, une amelioration progressive (significative) de la capacite de resolution visuelle a mesure que dure la privation et, apres la privation, un retour graduel vers le niveau de base. Par ailleurs, on n'observe aucun changement significatif chez deux groupes de contr61e (un groupe confine et un groupe non confine). Dans la seconde experience, la duree de la privation auditive atteint 14 jours. Les resultats relevent encore une amelioration progressive de la CFF pendant la premiere semaine de silence, la courbe devenant asymptotique pendant la seconde semaine. Ces resultats sont interpretes dans le contexte de la theorie sensoristatique de Schultz (1965) qui predit des effets mtersensoriels de renforcernent en fonction de la privation sensorielle. REFERENCES DODA, P., & ZUBEK, J.P. Auditory sensitivity after prolonged visual deprivation. Psychonom. Set., 1965, 3, 359-360.
1975]
AUDITORY DEPRIVATION
347
r, S.L., & ZUBEK, J.P. Temporal changes in cutaneous sensitivity during prolonged visual deprivation. Canad. J. Psychol, 1971, 25, 336-348. MYERS, J.L. Fundamentals of experimental design. Boston: Allyn & Bacon, 1966. PANGMAN, C.H., & ZUBEK, J.P. Changes in auditory flutter fusion frequency during prolonged visual deprivation. Percept. Psychophys., 1972, 11, 172-174. SCHULTZ, D.P. Sensory restriction: effects on behavior. New York: Academic Press, 1965. ZUBEK, J.P. (ed.) Sensory deprivation: fifteen years of research. New York: AppletonCentury-Crofts, 1969. ZUBEK, J.P., FLYE, J., & AFTANAS, M. Cutaneous sensitivity after prolonged visual deprivation. Science, 1964, 144,1591-1593. ZUBEK, J.P., FLYE, J., & WILLOWS, D.
Changes in cutaneous sensitivity after pro-
longed exposure to unpatterned light. Psychonom. Sci., 1964, 1, 283-284. (First received 6 March 1975) (Date accepted 15 August 1975)
