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Schedule-induced polydipsia under conditions of restricted access to water
Physiology & Behavior, Vol. 22, pp. 405-407. Pergamon Press and Brain Research Publ., 1979. Primed in the U.S.A.
Schedule-Induced Polydipsia Under Conditions of Restricted Access to Water ROBERT A. ROSELLINI
University o f Pennsylvania, Philadelphia, PA 19104 ( R e c e i v e d 24 D e c e m b e r 1977) ROSELLINI, R.A. Schedule-induced polydipsia under conditions of restricted access to water. PHYSIOL. BEHAV. 22(2)405--407, 1979.---Schedule-induced polydipsia has been observed when access to water is restricted to later portions of the inter-pellet interval. This argues against low probability of reinforcement being the sole controlling factor of this phenomenon and suggests that other factors, such as post-prandial and dry-mouth, may also play a role in scheduleinduced polydipsia. This experiment investigates the role of these other factors in a schedule-induced polydipsia situation where access to water is limited. Water was made available during two 10-see periods of each inter-pellet interval. In the last phase of the experiment, a 5-min pre-session access period was given. Two animals consumed water during both availability periods and also during the pre-session period, while a third animal drank only during the first post-pellet water presentation. The results extend the generality of schedule-induced polydipsia under conditions of limited access to water. Polydipsia Restricted water a c c e s s Fixed-time schedule Rats
Licking patterns
I F FOOD deprived animals are exposed to an intermittent schedule of food delivery, they typically ingest excessive amounts of water [2]. This phenomenon, known as schedule-induced polydipsia, has been obtained under a wide variety of schedules and magnitudes of reinforcement and deprivation conditions [3]. Schedule-induced polydipsia is largely a post-pellet phenomenon in that the majority of water intake occurs closely following consumption of the food pellet when water is continuously available [6]. It has been suggested that this pattern may be due to postingestional factors being strongest and probability of reinforcement being lowest immediately after pellet consumption [2]. To assess the validity o f this proposal, several investigators have restricted water availability to different portions of the inter-pellet interval. They have found drinking to occur whenever the animals had the opportunity to do so, although intake was somewhat attenuated when water availability was restricted to later portions of the inter-pellet interval [ 1, 4, 5]. This work suggests that factors other than low probability of reinforcement can control water intake under restricted access conditions. The low probability of reinforcement does not seem capable of accounting for the occurence of schedule-induced licking when water is unavailable during the early portions o f the inter-pellet interval. It has been proposed that post-prandial factors may also be important in this situation [2]. These post-prandial [8] and dry-mouth factors [7,9] may be sufficient to trigger the initiation of
Pre-session intake
Post-ingestional factors
drinking at any point during the inter-pellet interval when water is first made available. In order to assess this possibility, animals in the present experiment were given two exposures to water during each inter-pellet interval. Consumption of water during the first access period should eliminate or at least greatly attenuate the role of these p o s t p r a n d i a l and dry-mouth factors in intake during the subsequent access period. METHOD
Animals Three male albino rats obtained from Holtzman Co. were used. They were approximately I I0 days o f age and were reduced to 80% of their free feeding weight 7 days prior to the beginning of the experiment. Their deprivation weights ranged from 391-403 g. All animals were run during the light phase of a 12 hr light/12 hr dark cycle. They were housed in individual cages where water was continuously available.
Apparatus Three operant chambers were used. Each chamber was 30.5 cm long, 27.9 cm high, and 25.5 cm wide. The 2 side walls were clear Plexiglas and the front and back walls of aluminum. The floor consisted of stainless steel rods 0.32 cm in dia., spaced 1.30 cm apart. A food cup was centered on the front wall and rested on the floor. A 2 cm dia. hole was
~This research was supported by Post-doctoral Fellowship MH-00980 to the author and grant MH-29187 from the National Institute of Mental Health to Richard L. Solomon. The author wishes to thank Richard L. Solomon, Thomas D'Andrea, David R. Burdette, and Guy Woodruff for their helpful comments on an earlier draft of this article, and Laura M. Bell, for editorial assistance. Requests for reprints should be sent to Robert A. Rosellini, Department of Psychology, State University of New York at Albany, Albany NY 12222.
C o p y r i g h t © 1979 B r a i n R e s e a r c h P u b l i c a t i o n s Inc.--0031-9384/79/020405-03502.00/0
406
ROSELLIN I
located 3.8 cm to the right of the food cup. A 100 ml retractable drinking tube with a 2.5 mm orifice was located behind this aperture. In the inserted position, the stainless steel drinking spout was centered and 2 mm behind the access hole. In the withdrawn position, the tip of the spout rested 3 cm outside the chamber so that the animals could not make contact with it. The water in the tube and the grid floor of the chamber served as the 2 electrodes for the drinkometer circuit. Each chamber was housed in a sound and light attenuating container equipped with a house light, white masking noise, and a ventilation fan.
The second 10-sec period was systematically presented during later portions of the inter-pellet interval across the 3 phases. Phase 2 was conducted for 7 sessions. This consisted of making water available for a second 10-sec period 10 sec after termination of the first period. In Phase 3, which was conducted for 10 sessions, the second access was 40 sec following termination of the first. In Phase 4, which was also conducted for 10 sessions, the second access occured 70 sec following termination of the first. Thus the second access to water began either 30, 60, or 90 sec following pellet delivery in Phases 2, 3, and 4 respectively. Phase 5 was identical to Phase 4 with the exception that 5-min access to water was given prior to the start of the session. Five seconds prior to the delivery of the first pellet of the session, the drinking tube was retracted and the remainder of each session was identical to Phase 4 conditions. All sessions consisted of 30
Procedure
Prior to Session 1, a baseline water intake session was conducted in which 30 pellets were placed in the food cup and water was continuously available. The first phase of the experiment consisted of exposing the rats to 24 sessions in which one 45 nag Formula A Noyes pellet was delivered on a Fixed Time (FT) 120-sec schedule. The drinking tube was available throughout the inter pellet interval during this phase. During the next 3 phases, the tube was available only during 2 separate 10-sec periods of each interval. The first presentation occured 10 sec following the delivery of the pellet to allow time for the ingestion of the pellet. This access period was constant for the remainder of the experiment. Access
•
Ist
o
2nd Access
pellet deliveries. RESULTS
The 3 rats c o n s u m e d e x c e s s i v e and approximately equivalent amounts of water w h e n it w a s continuously available during the final 3 sessions o f Phase 1 ( 1 7 . 7 , 16.7, and 15.3ml). The mean percent increase from baseline intake to asymptotic mean intake on Sessions 22-24 w a s 152, 85, and
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F I G . 1. The columns labeled 1-5 represent the 5 phases of the experiment and the rows the behavior for each animal. The numbers
superimposed on the individual lick patterns in the left panel (Phase 1) show the temporal position of the second 10-see access period when water was available during Phases 2-4 respectively. Water intake (unconnected open triangle), and licks during the first (f'dled circle) and second (open circle) access periods are shown in columns 2-5. The filled triangles connected by broken lines in the right panel show the number of licks during the 5-rain pre-session period of Phase 5.
P O L Y D I P S I A A N D RESTRICTED W A T E R
407
155% for R124, R125, and R126 respectively. Panel 1 of Fig. 1 shows the mean total tube contacts in 10-sec blocks during the inter-pellet interval for Sessions 22-24. Although each animal showed an increase then decrease in tube contacts, they showed dissimilar distributions of tube contacts during the interval. R126 showed a highly peaked distribution with most contacts (81 per cent) occuring within 20 sec following pellet delivery and a rapid decrease over the next 20 sec period. This animal emitted 98% of its tube contacts within 40 sec after pellet delivery. R124 showed a more gradually changing distribution with the highest number of contacts occuring 30-50 sec following the pellet delivery (74%). R125 showed the fastest distribution with 10-20% of the contacts occuring from 30-80 sec following pellet delivery. All animals decreased their water intake during Phase 2 (Panel 2 of Fig. 1) when the second access to water occured 10 sec following termination of the first, as compared to their mean intake on Sessions 22-24. Although the animals consumed roughly equivalent amounts of water during Phase 2, their tube contacts distributions differed. Both R124 and R125 contacted the tube substantially more often during the second exposure than during the first. R126, however, restricted almost all its contacts to the first exposure period. In Phases 3 and 4 (Panels 3 and 4 of Fig. 1), when the second access was 40 and 70 sec following termination of the first, R124 and R125 increased their water intake as compared to when water was continuously available in Phase 1. Both these animals also showed a tendency to increase their contacts during the first exposure period so that approximately equivalent contacts were given during both access periods. As in Phase 2, R126 restricted most tube contacts to the first access period and showed no change in water intake. In general, limiting access to water increased the number of contacts made during that 10-sec portion of the inter-pellet interval over the level seen when water was continuously available. There was a tendency in all animals to aportion more contacts to that segment of the inter-pellet interval where contacts were highest during the continuous access condition. F o r example, almost all the tube contacts of R 126 were observed in the first access period throughout all phases of the e x p e r i m e n t - - t h e same period in which the greatest number of tube contacts occured during continuous access. When the 2 access periods occured during portions of the interval where contacts were low during continuous access conditions (Phases 3 and 4 for R124 and Phase 4 for R125), the number of contacts increased equally in both periods. The introduction of the 5-min pre-session access to water in Phase 5 (Panel 5 of Fig. 1) seems to have had little effect on either the total amount of water consumed or the total
number of contacts. However, this manipulation tended to separate the distributions of contacts obtained in the 2 access periods for the 2 animals (R124 and R125) which consumed water during this pre-session period. R124 initially decreased both water intake and contacts with a recovery and differentiation of contact distribution in subsequent sessions. During the latter sessions of this phase, both R124 and R125 emitted more contacts during the second access period. R126, which did not consume water during the pre-session period, limited its tube contacts to the first access period, as in the previous phases of the experiment. DISCUSSION Animals will not only consume water whenever it is made available under these conditions, they will also initiate more than one drinking bout per interval when water is available for only short periods of time. This observation further expands the generality of the schedule-induced polydipsia phenomenon. Both R124 and R125 greatly increased their tube contact during each of the two access periods as compared to that during comparable periods under free access conditions. Restricting water availability, then, seems to potentiate contacts during periods when such contacts would normally be more probable. A similar potentiation has been observed when water was available for only one 10-sec period of each inter-pellet interval [5]. It seems unlikely that post-prandial and dry-mouth factors played an important role in the control of drinking in these 2 animals (R124 and R125). Both animals consumed water during each access period throughout all phases of the experiment. The water consumed during the initial exposure should attenuate if not completely remove the influence of these factors. However, both animals consumed water and often showed a higher incidence of contacts during the second exposure, relative to the first exposure. In addition, both these animals also ingested water during the 5-min presession exposure in Phase 5. Intake during this period could not be under the influence of post-ingestional factors since no food pellets had been presented. Water intake for R126, however, may have been strongly controlled by postingestional factors. When access to water was limited, this animal reduced intake to baseline levels, restricted tube contacts to the period immediately following pellet delivery, and water consumption during the pre-session period of Phase 5 was extremely low. A similar decrease in intake and restriction of tube contacts to the early portions of the interval has been observed by others when water availability was limited to one 10-sec period of the inter-pellet interval [5]. Thus, it appears that water intake for some animals may be strongly controlled by post-ingestional factors.
REFERENCES l. Daniel, W. and G. D. King. The consequences of restricted water accessibility on schedule-induced polydipsia. Bull. Psychon. Soc. 5: 297-299, 1975. 2. Falk, J. L. Conditions producing psychogenic polydipsia in animals. Ann. N. Y. Acad. Sci. 157: 569-593, 1969. 3. Falk, J. L. The nature and determinants of adjunctive behavior. In: Schedule Effects: Drugs, Drinking, and Aggression, edited by R. M. Gilbert and J. D. Keehn, Toronto: University of Toronto Press, 1972, pp. 148-173. 4. Flory, R. K. and M. K. O'Boyl¢. The effect of limited water availability on schedule-induced polydipsia. Physiol. Behav. 8: 147-149, 1972. 5. Gilbert, R. M. The ubiquity of schedule-induced polydipsia. J. exp. Analysis. Behav. 21: 227-234, 1974.
6. Staddon, J. E. R. and S. L. Ayres. Sequential and temporal properties of behavior induced by a schedule of periodic food delivery. Behavior 54: 26--49, 1975. 7. Stein, L. Excessive drinking in the rat: Superstition or thirst? J. comp. physiol. Psychol. 58: 237-242, 1964. 8. Stricker, E. M. and E. R. Adair. Body fluid balance, taste, and post-prandial factors in schedule-induced polydipsia. J. comp. physiol. Psychol. 62: 449--454, 1966. 9. Teitelbaum, P. The use of operant methods in the assessment and control of motivational states. In: Operant Behavior: Areas of Research and Application, edited by W. K. Honig. New York: Meredith, 1966.
Schedule-Induced Polydipsia Under Conditions of Restricted Access to Water ROBERT A. ROSELLINI
University o f Pennsylvania, Philadelphia, PA 19104 ( R e c e i v e d 24 D e c e m b e r 1977) ROSELLINI, R.A. Schedule-induced polydipsia under conditions of restricted access to water. PHYSIOL. BEHAV. 22(2)405--407, 1979.---Schedule-induced polydipsia has been observed when access to water is restricted to later portions of the inter-pellet interval. This argues against low probability of reinforcement being the sole controlling factor of this phenomenon and suggests that other factors, such as post-prandial and dry-mouth, may also play a role in scheduleinduced polydipsia. This experiment investigates the role of these other factors in a schedule-induced polydipsia situation where access to water is limited. Water was made available during two 10-see periods of each inter-pellet interval. In the last phase of the experiment, a 5-min pre-session access period was given. Two animals consumed water during both availability periods and also during the pre-session period, while a third animal drank only during the first post-pellet water presentation. The results extend the generality of schedule-induced polydipsia under conditions of limited access to water. Polydipsia Restricted water a c c e s s Fixed-time schedule Rats
Licking patterns
I F FOOD deprived animals are exposed to an intermittent schedule of food delivery, they typically ingest excessive amounts of water [2]. This phenomenon, known as schedule-induced polydipsia, has been obtained under a wide variety of schedules and magnitudes of reinforcement and deprivation conditions [3]. Schedule-induced polydipsia is largely a post-pellet phenomenon in that the majority of water intake occurs closely following consumption of the food pellet when water is continuously available [6]. It has been suggested that this pattern may be due to postingestional factors being strongest and probability of reinforcement being lowest immediately after pellet consumption [2]. To assess the validity o f this proposal, several investigators have restricted water availability to different portions of the inter-pellet interval. They have found drinking to occur whenever the animals had the opportunity to do so, although intake was somewhat attenuated when water availability was restricted to later portions of the inter-pellet interval [ 1, 4, 5]. This work suggests that factors other than low probability of reinforcement can control water intake under restricted access conditions. The low probability of reinforcement does not seem capable of accounting for the occurence of schedule-induced licking when water is unavailable during the early portions o f the inter-pellet interval. It has been proposed that post-prandial factors may also be important in this situation [2]. These post-prandial [8] and dry-mouth factors [7,9] may be sufficient to trigger the initiation of
Pre-session intake
Post-ingestional factors
drinking at any point during the inter-pellet interval when water is first made available. In order to assess this possibility, animals in the present experiment were given two exposures to water during each inter-pellet interval. Consumption of water during the first access period should eliminate or at least greatly attenuate the role of these p o s t p r a n d i a l and dry-mouth factors in intake during the subsequent access period. METHOD
Animals Three male albino rats obtained from Holtzman Co. were used. They were approximately I I0 days o f age and were reduced to 80% of their free feeding weight 7 days prior to the beginning of the experiment. Their deprivation weights ranged from 391-403 g. All animals were run during the light phase of a 12 hr light/12 hr dark cycle. They were housed in individual cages where water was continuously available.
Apparatus Three operant chambers were used. Each chamber was 30.5 cm long, 27.9 cm high, and 25.5 cm wide. The 2 side walls were clear Plexiglas and the front and back walls of aluminum. The floor consisted of stainless steel rods 0.32 cm in dia., spaced 1.30 cm apart. A food cup was centered on the front wall and rested on the floor. A 2 cm dia. hole was
~This research was supported by Post-doctoral Fellowship MH-00980 to the author and grant MH-29187 from the National Institute of Mental Health to Richard L. Solomon. The author wishes to thank Richard L. Solomon, Thomas D'Andrea, David R. Burdette, and Guy Woodruff for their helpful comments on an earlier draft of this article, and Laura M. Bell, for editorial assistance. Requests for reprints should be sent to Robert A. Rosellini, Department of Psychology, State University of New York at Albany, Albany NY 12222.
C o p y r i g h t © 1979 B r a i n R e s e a r c h P u b l i c a t i o n s Inc.--0031-9384/79/020405-03502.00/0
406
ROSELLIN I
located 3.8 cm to the right of the food cup. A 100 ml retractable drinking tube with a 2.5 mm orifice was located behind this aperture. In the inserted position, the stainless steel drinking spout was centered and 2 mm behind the access hole. In the withdrawn position, the tip of the spout rested 3 cm outside the chamber so that the animals could not make contact with it. The water in the tube and the grid floor of the chamber served as the 2 electrodes for the drinkometer circuit. Each chamber was housed in a sound and light attenuating container equipped with a house light, white masking noise, and a ventilation fan.
The second 10-sec period was systematically presented during later portions of the inter-pellet interval across the 3 phases. Phase 2 was conducted for 7 sessions. This consisted of making water available for a second 10-sec period 10 sec after termination of the first period. In Phase 3, which was conducted for 10 sessions, the second access was 40 sec following termination of the first. In Phase 4, which was also conducted for 10 sessions, the second access occured 70 sec following termination of the first. Thus the second access to water began either 30, 60, or 90 sec following pellet delivery in Phases 2, 3, and 4 respectively. Phase 5 was identical to Phase 4 with the exception that 5-min access to water was given prior to the start of the session. Five seconds prior to the delivery of the first pellet of the session, the drinking tube was retracted and the remainder of each session was identical to Phase 4 conditions. All sessions consisted of 30
Procedure
Prior to Session 1, a baseline water intake session was conducted in which 30 pellets were placed in the food cup and water was continuously available. The first phase of the experiment consisted of exposing the rats to 24 sessions in which one 45 nag Formula A Noyes pellet was delivered on a Fixed Time (FT) 120-sec schedule. The drinking tube was available throughout the inter pellet interval during this phase. During the next 3 phases, the tube was available only during 2 separate 10-sec periods of each interval. The first presentation occured 10 sec following the delivery of the pellet to allow time for the ingestion of the pellet. This access period was constant for the remainder of the experiment. Access
•
Ist
o
2nd Access
pellet deliveries. RESULTS
The 3 rats c o n s u m e d e x c e s s i v e and approximately equivalent amounts of water w h e n it w a s continuously available during the final 3 sessions o f Phase 1 ( 1 7 . 7 , 16.7, and 15.3ml). The mean percent increase from baseline intake to asymptotic mean intake on Sessions 22-24 w a s 152, 85, and
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Sessions
F I G . 1. The columns labeled 1-5 represent the 5 phases of the experiment and the rows the behavior for each animal. The numbers
superimposed on the individual lick patterns in the left panel (Phase 1) show the temporal position of the second 10-see access period when water was available during Phases 2-4 respectively. Water intake (unconnected open triangle), and licks during the first (f'dled circle) and second (open circle) access periods are shown in columns 2-5. The filled triangles connected by broken lines in the right panel show the number of licks during the 5-rain pre-session period of Phase 5.
P O L Y D I P S I A A N D RESTRICTED W A T E R
407
155% for R124, R125, and R126 respectively. Panel 1 of Fig. 1 shows the mean total tube contacts in 10-sec blocks during the inter-pellet interval for Sessions 22-24. Although each animal showed an increase then decrease in tube contacts, they showed dissimilar distributions of tube contacts during the interval. R126 showed a highly peaked distribution with most contacts (81 per cent) occuring within 20 sec following pellet delivery and a rapid decrease over the next 20 sec period. This animal emitted 98% of its tube contacts within 40 sec after pellet delivery. R124 showed a more gradually changing distribution with the highest number of contacts occuring 30-50 sec following the pellet delivery (74%). R125 showed the fastest distribution with 10-20% of the contacts occuring from 30-80 sec following pellet delivery. All animals decreased their water intake during Phase 2 (Panel 2 of Fig. 1) when the second access to water occured 10 sec following termination of the first, as compared to their mean intake on Sessions 22-24. Although the animals consumed roughly equivalent amounts of water during Phase 2, their tube contacts distributions differed. Both R124 and R125 contacted the tube substantially more often during the second exposure than during the first. R126, however, restricted almost all its contacts to the first exposure period. In Phases 3 and 4 (Panels 3 and 4 of Fig. 1), when the second access was 40 and 70 sec following termination of the first, R124 and R125 increased their water intake as compared to when water was continuously available in Phase 1. Both these animals also showed a tendency to increase their contacts during the first exposure period so that approximately equivalent contacts were given during both access periods. As in Phase 2, R126 restricted most tube contacts to the first access period and showed no change in water intake. In general, limiting access to water increased the number of contacts made during that 10-sec portion of the inter-pellet interval over the level seen when water was continuously available. There was a tendency in all animals to aportion more contacts to that segment of the inter-pellet interval where contacts were highest during the continuous access condition. F o r example, almost all the tube contacts of R 126 were observed in the first access period throughout all phases of the e x p e r i m e n t - - t h e same period in which the greatest number of tube contacts occured during continuous access. When the 2 access periods occured during portions of the interval where contacts were low during continuous access conditions (Phases 3 and 4 for R124 and Phase 4 for R125), the number of contacts increased equally in both periods. The introduction of the 5-min pre-session access to water in Phase 5 (Panel 5 of Fig. 1) seems to have had little effect on either the total amount of water consumed or the total
number of contacts. However, this manipulation tended to separate the distributions of contacts obtained in the 2 access periods for the 2 animals (R124 and R125) which consumed water during this pre-session period. R124 initially decreased both water intake and contacts with a recovery and differentiation of contact distribution in subsequent sessions. During the latter sessions of this phase, both R124 and R125 emitted more contacts during the second access period. R126, which did not consume water during the pre-session period, limited its tube contacts to the first access period, as in the previous phases of the experiment. DISCUSSION Animals will not only consume water whenever it is made available under these conditions, they will also initiate more than one drinking bout per interval when water is available for only short periods of time. This observation further expands the generality of the schedule-induced polydipsia phenomenon. Both R124 and R125 greatly increased their tube contact during each of the two access periods as compared to that during comparable periods under free access conditions. Restricting water availability, then, seems to potentiate contacts during periods when such contacts would normally be more probable. A similar potentiation has been observed when water was available for only one 10-sec period of each inter-pellet interval [5]. It seems unlikely that post-prandial and dry-mouth factors played an important role in the control of drinking in these 2 animals (R124 and R125). Both animals consumed water during each access period throughout all phases of the experiment. The water consumed during the initial exposure should attenuate if not completely remove the influence of these factors. However, both animals consumed water and often showed a higher incidence of contacts during the second exposure, relative to the first exposure. In addition, both these animals also ingested water during the 5-min presession exposure in Phase 5. Intake during this period could not be under the influence of post-ingestional factors since no food pellets had been presented. Water intake for R126, however, may have been strongly controlled by postingestional factors. When access to water was limited, this animal reduced intake to baseline levels, restricted tube contacts to the period immediately following pellet delivery, and water consumption during the pre-session period of Phase 5 was extremely low. A similar decrease in intake and restriction of tube contacts to the early portions of the interval has been observed by others when water availability was limited to one 10-sec period of the inter-pellet interval [5]. Thus, it appears that water intake for some animals may be strongly controlled by post-ingestional factors.
REFERENCES l. Daniel, W. and G. D. King. The consequences of restricted water accessibility on schedule-induced polydipsia. Bull. Psychon. Soc. 5: 297-299, 1975. 2. Falk, J. L. Conditions producing psychogenic polydipsia in animals. Ann. N. Y. Acad. Sci. 157: 569-593, 1969. 3. Falk, J. L. The nature and determinants of adjunctive behavior. In: Schedule Effects: Drugs, Drinking, and Aggression, edited by R. M. Gilbert and J. D. Keehn, Toronto: University of Toronto Press, 1972, pp. 148-173. 4. Flory, R. K. and M. K. O'Boyl¢. The effect of limited water availability on schedule-induced polydipsia. Physiol. Behav. 8: 147-149, 1972. 5. Gilbert, R. M. The ubiquity of schedule-induced polydipsia. J. exp. Analysis. Behav. 21: 227-234, 1974.
6. Staddon, J. E. R. and S. L. Ayres. Sequential and temporal properties of behavior induced by a schedule of periodic food delivery. Behavior 54: 26--49, 1975. 7. Stein, L. Excessive drinking in the rat: Superstition or thirst? J. comp. physiol. Psychol. 58: 237-242, 1964. 8. Stricker, E. M. and E. R. Adair. Body fluid balance, taste, and post-prandial factors in schedule-induced polydipsia. J. comp. physiol. Psychol. 62: 449--454, 1966. 9. Teitelbaum, P. The use of operant methods in the assessment and control of motivational states. In: Operant Behavior: Areas of Research and Application, edited by W. K. Honig. New York: Meredith, 1966.