- Email: [email protected]
Schedule-induced defecation: A demonstration in pigeons exposed to fixed-time schedules of food delivery
Physiology& Behavior,Vol. 58, No. 1, pp. 195-198, 1995 Copyright© 1995ElsevierScienceLid Printedin the USA.All fightsreserved 0031-9384/95$9.50 + .00
Pergamon 0031-9384(95)00042-9
BRIEF COMMUNICATION
Schedule-Induced Defecation: A Demonstration in Pigeons Exposed to Fixed-Time Schedules of Food Delivery K I M B E R L Y J A R E M A , M A R K LESAGE A N D A L A N P O L I N G 1
Department of Psychology, Western Michigan University, Kalamazoo, M I 49008, USA Received 6 September 1994
JAREMA, K., M. LESAGE AND A. POLING. Schedule-induceddefecation: A demonstration in pigeons exposed to fixed-time schedules of food delivery. PHYSIOL BEHAV 58(1) 195-198, 1995.--Previous studies have found that defecation increases in rats exposed to intermittent schedules of food delivery. In the present study, food-deprivedpigeons were exposed to fixed-time 30-, 60-, 120-, and 240-s schedules of food delivery. For the subjects as a group, significantlymore defecation (indexed by fecal weight) occurred under the fixed-time60-s schedule than during massed-foodcontrol sessions in which an equivalent amount of food was presented. Thus, the present findings suggest that schedule-induceddefecation occurs in pigeons. Schedule-induceddefecation
Fixed-timeschedules
Pigeons
WHEN food-deprived rats are exposed to intermittent schedules of food delivery, they drink copious amounts of water (2). This polydipsia is the prototype of a class of behaviors called adjunctive or schedule-induced (3). Other putative adjunctive behaviors include pica, attack, wheel running, biting, chewing, grooming, locomotion, chain pulling, drug ingestion, and pecking (4,10,11,13), although not all authors agree that ~aese behaviors share common features. Four previous studies, all with rats, suggest that scbeduleinduced defecation also is adjunctive behavior (6,9,15,16). In those studies, intermittent food delivery under several different schedules substantially increased the number of fecal boli produced by rats relative to massed-food and no-food baseline levels. To date, schedule-hnduced defecation has not been demonstrated in other species. The purpose of the present study was to examine whether schedule-induced defecation occurs in pigeons exposed to schedules of food delivery similar to those that induced defecation in rats in a previous study from our laboratory (6). Because pigeons characteristically produce large and soft stools, not firm and discrete boil like those of rats, fecal weight was used to index defecation in the birds.
bird had previously served in behavioral pharmacology experiments, but not within the 6 mo prior to the present study. They were individually housed in a colony area with controlled lighting (16 h light, 8 h dark each day), temperature (22-24°C), and humidity (60-70%).
Apparatus Four Lehigh Valley Electronics (BRS/LVE, Lehigh Valley, PA) operant conditioning chambers, measuring 32 cm high, 36 cm wide, and 35 cm high, were used. An aperture horizontally centered in the front wall 7.5 cm above the floor allowed access to a hopper filled with Purina Pigeon Grain (Ralston-Purina, St. Louis) when the hopper was raised. The raised hopper was illuminated by a 7-W white bulb. A paper cone, approximately 2.5 cm deep and 5 cm in diameter, was placed in the feeder aperture during massed-food sessions. Purina Pigeon Grain was placed in this cone during such sessions. A 7-W white bulb (houseligh0 centered on the chamber's ceiling provided ambient illumination and an exhaust fan supplied masking noise and ventilation. Individual speakers mounted in each chamber also provided masking noise. Control of experimental events and data recording were accomplished through the use of an ALR Flyer 32DT computer (Advanced Logic Research, Irvine, CA) using MED-PC Software (MED Associates, St. Albans, VT).
METHOD
Subjects Four White Carneau pigeons, maintained at 80% of free-feeding body weights throughout the study, served as subjects. Each 1To whom requests for reprints should be addressed.
195
196
JAREMA, LESAGE AND POLING
TABLE 1 NUMBER OF SESSIONSOF EXPOSURETO EXPERIMENTALCONDITIONS
Procedure Initially, all subjects were hopper trained under a random-time 60-s schedule of food delivery for 15 consecutive sessions. Under this schedule, food was delivered for 3 s on average once every 60 s, although the time between consecutive food deliveries varied. Sessions were conducted daily, and ended after 30 food deliveries. Prior to and after each session, the amount of food contained in the food hopper was weighed and recorded. The mean difference in these values during the final 10 sessions of exposure to the random-time 60-s schedule was used to determine the amount of food each bird consumed given 30 3-s presentations. These values, which constitute the amount of food presented in all massed-food baseline sessions, were 9.5, 9.1, 7.1, and 10.7 g for subjects B1, B2, B3, and B4, respectively. In all conditions, each bird was exposed to one experimental session per day, at about the same time each day. Following exposure to the random-time 60-s schedule, all subjects were exposed to alternating massed-food baseline and FT schedule conditions. Each FT session ended after 30 3-s food deliveries and each massed-food session was equal in length to the FT sessions for which it served as baseline. The first massedfood condition was the FT 60-s baseline, and involved 30-min sessions in which an amount of food equal to that consumed in 30 3-s food deliveries was presented at the beginning of the session. The first FT condition was FT 60-s. Under this schedule, food was presented for 3 s every 60 s, regardless of the bird's behavior. Each FT 60-s session ended after 30 min (30 food deliveries). Two randomly selected birds began the experiment in the FT 60-s condition. The other two began it in the massedfood condition. These and all other experimental conditions were in effect until visual inspection of graphed data indicated that the weight of feces deposited by each bird showed no trend across l0 consecutive sessions. The number of sessions during which each bird was exposed to each experimental condition is shown in Table 1. During all sessions, the chamber was illuminated when the session began, and was darkened when the session ended. Visual inspection of the data obtained under the F'l" 60-s and its massed-food comparison condition suggested that scheduleinduced defecation occurred. Therefore, other FT values were examined. In subsequent conditions, FT 30-, 120-, and 240-s schedules and their associated massed-food baselines were evaluated. These evaluations were comparable to those described above, with the exception of session duration, which was 15 min for the FT 30-s and its massed-food baseline, 60 rain for the FT 120-s and its massed-food baseline, and 120 min for the FR 240s and its massed-food baseline. Exposure to FT values other than 60-s was arranged in random order across subjects. Throughout the study, birds were removed from the chamber as soon as sessions ended. Fecal weights were determined by weighing a clean sheet of paper prior to each session, placing this paper on the floor of the cage at the beginning of the session, weighing the paper at the end of the session, and subtracting the beginning weight from the ending weight. Any fecal material adhering to other parts of the chamber at session's end were placed on the paper for weighing. Weighing was accomplished via a triple-beam balance, with weights rounded to the nearest 0.1g.
RESULTS Figure 1 shows average weight of feces deposited each day by each subject under each FT schedule and its corresponding massed-food baseline condition. Similar patterns were evident in
Subject Condition
Session Duration
B1
B2
B3
B4
Massed Food PT 30 s Massed Food PT 60 s Massed Food PT 120 s Massed Food PT 240 s
15 min 15 min 30 min 30 min 60 min 60 min 120 min 120 min
22 10 20 13 32 10 19 11
10 10 14 12 17 12 10 12
10 10 14 14 15 11 17 13
10 23 13 14 14 16 12 10
the data for three birds (B2, B3, B4). For those birds, the amount of defecation increased directly with the value of the FT. Moreover, for those birds, a greater amount of fecal material was deposited under the FT 60-s and 120-s schedule conditions than under equal-length massed-food baseline sessions. At these F1r values, standard deviations of mean grams of feces deposited during FT and control sessions did not overlap. For the fourth subject (B 1), defecation increased with FT value from PT 60- to FT 240-s, but a greater amount of feces was deposited at FT 30s than at any other schedule value. For that bird, standard deviations of mean grams of feces deposited during FT and control sessions overlapped at all FT values. Repeated measures analysis of variance was used to analyze data for the subjects as a group. There was a significant overall effect across conditions (F = 5.624, p = 0.0001). Paired t-tests, which are appropriate when few planned comparisons are of interest (5), were used to compare Fir 60-s and FT 120-s schedule group means to appropriate massed-food means. These tests revealed that the mean fecal weight for the subjects as a group significantly exceeded the massed-food baseline level at PT 60 s (t = -2.76, p = 0.009), but not at PT 120 s (t = -0.548, p = 0.587).
DISCUSSION A significant increase in defecation under FF schedule conditions relative to massed-food conditions is suggestive of schedule-induced defecation, and such an effect was evident in the present study when the P-T value was 60 s. However, even at that value, relatively little defecation occurred (i.e., the behavior was not clearly "excessive"), and it appeared that the birds emitted relatively few ( < 5) droppings per session. Schedule-induced polydipsia in rats, the prototype of adjunctive behavior, is clearly excessive and occurs after most food deliveries (3). Moreover, schedule-induced polydipsia and other adjunctive behaviors characteristically occur soon after food is consumed (3), but the temporal pattern of schedule-induced defecation in pigeons is unknown. Given these considerations, it is premature to consider schedule-induced defecation in pigeons as comparable to schedule-induced polydipsia in rats, or to other examples of adjunctive behavior. Interestingly, schedule-induced polydipsia occurs in pigeons (7,12), but it is not always observed under conditions where it is easily produced in rats (1,8,14,17). Given this, it of interest that the present study demonstrated schedule-induced defecation in pigeons under conditions roughly comparable to those that produced it previously in rats tested in our laboratory (6) and else-
DEFECATION IN PIGEONS
197
B2
B1 10-
[]
Massed-FoodDefecation
[]
P-T Defecation
7.5-
:::::: .,,o,,, .,,,-,, ..,,-,, ,,.,.,
5-
,o°.-, ,.-.,, ,.,.,, .,.°,,, .,.,,., -,-,,., .,,,,,,
m t-
2.5-
,.,,-. ,.,,,. ,,,,,. ,,,.,. .,,.,, .,,.,. .,..., -,,,-,, ,,-,-,, ,,..., ,,-,,, ,,,..-
0
!
!
!
¢*w
o
B4
B3 .$
1.5-
m
1.25 -
1"
I 0.75 i 0.5 "~
0.25 I
30
60
120
240
30
60
120
240
F i x e d - T i m e Value (sec) FIG. 1. l~[ean weight (in grams, plus one standard deviation) of feces produced by individual pigeons during the final 10 sessions of exposure to all experimental conditions. Dark bars indicate defecation when the listed fixedtime (FT) schedule of food delivery was in effect; light bars indicate defecation during the appropriate massedfood baseline for the listed FT schedule. The absence of a bar indicates no defecation. Each FT session ended after 30 food deliveries (e.g., 15 rain under FT 15 s, 120 min under FR 240 s). Massed-food sessions were equal in length to FT comparison sessions. In massed-food sessions, an amount of food (grain) approximately equal to that consumed in an ~ comparison session was presented in bulk at the beginning of the session and remained available until it was consumed, or the session ended. Note that values on the ordinate for subjects B1 and B2 are different 15aan those for subjects B3 and B4.
where (16). In those studies, as in the present one, an FT 60-s schedule induced defecal5on. In another study with rats, however, defecation was significa~atly elevated by exposure to an FT 32-s schedule, and there was no evidence that an FT 30-s schedule increased pigeons' defecation in the present study. Moreover, in
one of the four pigeons, there was no evidence of schedule-induced defecation at any FT value. Although schedule-induced defecation in pigeons appears to be real, further research is clearly required to delineate its specific characteristics and the variables that control it.
REFERENCES 1. Dale, R. H. I. Concurrent drinking by pigeons on fixed-interval reinforcement schedules. Physiol. Behav. 6:977-980; 1979. 2. Falk, J. L. Production of polydipsia in normal rats by an intermittent food schedule. Science 133:195-196;1961. 3. Falk, J. L. The nature and determinants of adjunctive behavior. Physiol. Behav. 6:577-588;1971.
4. Falk, J. L. The environmental generation of excessive behavior. In: Mule, S. J., ed. Behavior in excess: An examination of the volitional disorders. N e w York: Free Press; 1981:313337. 5. Howell, D. C. Statistical methods for psychology. Boston: Duxbury; 1987.
198
6. LeSage, M.; Makhay, M.; DeLeon, I.; Poling, A. The effects of damphetamine and diazepam on schedule-induced defecation in rats. Pharmacol. Biochem. Behav. 48:787-790;1994. 7. Magyar, R. L.; Malagodi, E. F. Measurement and development of schedule-induced drinking in pigeons. Physiol. Behav. 25:245251;1980. 8. Miller, J. S.; Gollub, L. R. Adjunctive and operant bolt-pecking in the pigeon. Psych. Record 24:203-208; 1974. 9. Rayfield, F.; Segal, M.; Goldiamond, I. Schedule-induced defecation. J. Exp. Anal. Behav. 38:19-34;1982. 10. Roper, T. J. What is meant by the term "schedule-induced," and how general is schedule induction? Anita. Learn. Behav. 9:433-440;1981. 11. Sanger, D. J. Drug taking as adjunctive behavior. In: Goldberg, S. R.; Stolerman, I. P., eds.; Behavioral analysis of drug dependence. New York: Academic Press; 1986:123-160.
JAREMA, LESAGE AND POLING
12. Shanab, M. E.; Peterson, J. L. Polydipsia in the pigeon. Psychon. Sci. 15:51-52;1969. 13. Wetherington, C. L. Is adjunctive behavior a third class of behavior? Neurosci. Biobehav. Rev. 6:329-350;1982. 14. Whalen, T. E.; Wilkie. D. M. Failure to find schedule-induced polydipsia in the pigeon. Bull. Psychon. Soc. 10:200-202;1977. 15. Wylie, A. M.; Layng, M. P.; Meyer, K. A. Schedule-induced defecation by rats during ratio and interval schedules of food reinforcement. J. Exp. Anal. Behav. 60:611-620;1993. 16. Wylie, A. M.; Springis, R.; Johnson, K. S. Schedule-induced defecation:No-food and massed-food baselines. J. Exp. Anal. Behav. 58:389-397;1992. 17. Yobum, B. C.; Cohen, P. S. Assessment of attack and drinking in White King on response-independent food schedules. J. Exp. Anal. Behav. 31:91-101;1979.
Pergamon 0031-9384(95)00042-9
BRIEF COMMUNICATION
Schedule-Induced Defecation: A Demonstration in Pigeons Exposed to Fixed-Time Schedules of Food Delivery K I M B E R L Y J A R E M A , M A R K LESAGE A N D A L A N P O L I N G 1
Department of Psychology, Western Michigan University, Kalamazoo, M I 49008, USA Received 6 September 1994
JAREMA, K., M. LESAGE AND A. POLING. Schedule-induceddefecation: A demonstration in pigeons exposed to fixed-time schedules of food delivery. PHYSIOL BEHAV 58(1) 195-198, 1995.--Previous studies have found that defecation increases in rats exposed to intermittent schedules of food delivery. In the present study, food-deprivedpigeons were exposed to fixed-time 30-, 60-, 120-, and 240-s schedules of food delivery. For the subjects as a group, significantlymore defecation (indexed by fecal weight) occurred under the fixed-time60-s schedule than during massed-foodcontrol sessions in which an equivalent amount of food was presented. Thus, the present findings suggest that schedule-induceddefecation occurs in pigeons. Schedule-induceddefecation
Fixed-timeschedules
Pigeons
WHEN food-deprived rats are exposed to intermittent schedules of food delivery, they drink copious amounts of water (2). This polydipsia is the prototype of a class of behaviors called adjunctive or schedule-induced (3). Other putative adjunctive behaviors include pica, attack, wheel running, biting, chewing, grooming, locomotion, chain pulling, drug ingestion, and pecking (4,10,11,13), although not all authors agree that ~aese behaviors share common features. Four previous studies, all with rats, suggest that scbeduleinduced defecation also is adjunctive behavior (6,9,15,16). In those studies, intermittent food delivery under several different schedules substantially increased the number of fecal boli produced by rats relative to massed-food and no-food baseline levels. To date, schedule-hnduced defecation has not been demonstrated in other species. The purpose of the present study was to examine whether schedule-induced defecation occurs in pigeons exposed to schedules of food delivery similar to those that induced defecation in rats in a previous study from our laboratory (6). Because pigeons characteristically produce large and soft stools, not firm and discrete boil like those of rats, fecal weight was used to index defecation in the birds.
bird had previously served in behavioral pharmacology experiments, but not within the 6 mo prior to the present study. They were individually housed in a colony area with controlled lighting (16 h light, 8 h dark each day), temperature (22-24°C), and humidity (60-70%).
Apparatus Four Lehigh Valley Electronics (BRS/LVE, Lehigh Valley, PA) operant conditioning chambers, measuring 32 cm high, 36 cm wide, and 35 cm high, were used. An aperture horizontally centered in the front wall 7.5 cm above the floor allowed access to a hopper filled with Purina Pigeon Grain (Ralston-Purina, St. Louis) when the hopper was raised. The raised hopper was illuminated by a 7-W white bulb. A paper cone, approximately 2.5 cm deep and 5 cm in diameter, was placed in the feeder aperture during massed-food sessions. Purina Pigeon Grain was placed in this cone during such sessions. A 7-W white bulb (houseligh0 centered on the chamber's ceiling provided ambient illumination and an exhaust fan supplied masking noise and ventilation. Individual speakers mounted in each chamber also provided masking noise. Control of experimental events and data recording were accomplished through the use of an ALR Flyer 32DT computer (Advanced Logic Research, Irvine, CA) using MED-PC Software (MED Associates, St. Albans, VT).
METHOD
Subjects Four White Carneau pigeons, maintained at 80% of free-feeding body weights throughout the study, served as subjects. Each 1To whom requests for reprints should be addressed.
195
196
JAREMA, LESAGE AND POLING
TABLE 1 NUMBER OF SESSIONSOF EXPOSURETO EXPERIMENTALCONDITIONS
Procedure Initially, all subjects were hopper trained under a random-time 60-s schedule of food delivery for 15 consecutive sessions. Under this schedule, food was delivered for 3 s on average once every 60 s, although the time between consecutive food deliveries varied. Sessions were conducted daily, and ended after 30 food deliveries. Prior to and after each session, the amount of food contained in the food hopper was weighed and recorded. The mean difference in these values during the final 10 sessions of exposure to the random-time 60-s schedule was used to determine the amount of food each bird consumed given 30 3-s presentations. These values, which constitute the amount of food presented in all massed-food baseline sessions, were 9.5, 9.1, 7.1, and 10.7 g for subjects B1, B2, B3, and B4, respectively. In all conditions, each bird was exposed to one experimental session per day, at about the same time each day. Following exposure to the random-time 60-s schedule, all subjects were exposed to alternating massed-food baseline and FT schedule conditions. Each FT session ended after 30 3-s food deliveries and each massed-food session was equal in length to the FT sessions for which it served as baseline. The first massedfood condition was the FT 60-s baseline, and involved 30-min sessions in which an amount of food equal to that consumed in 30 3-s food deliveries was presented at the beginning of the session. The first FT condition was FT 60-s. Under this schedule, food was presented for 3 s every 60 s, regardless of the bird's behavior. Each FT 60-s session ended after 30 min (30 food deliveries). Two randomly selected birds began the experiment in the FT 60-s condition. The other two began it in the massedfood condition. These and all other experimental conditions were in effect until visual inspection of graphed data indicated that the weight of feces deposited by each bird showed no trend across l0 consecutive sessions. The number of sessions during which each bird was exposed to each experimental condition is shown in Table 1. During all sessions, the chamber was illuminated when the session began, and was darkened when the session ended. Visual inspection of the data obtained under the F'l" 60-s and its massed-food comparison condition suggested that scheduleinduced defecation occurred. Therefore, other FT values were examined. In subsequent conditions, FT 30-, 120-, and 240-s schedules and their associated massed-food baselines were evaluated. These evaluations were comparable to those described above, with the exception of session duration, which was 15 min for the FT 30-s and its massed-food baseline, 60 rain for the FT 120-s and its massed-food baseline, and 120 min for the FR 240s and its massed-food baseline. Exposure to FT values other than 60-s was arranged in random order across subjects. Throughout the study, birds were removed from the chamber as soon as sessions ended. Fecal weights were determined by weighing a clean sheet of paper prior to each session, placing this paper on the floor of the cage at the beginning of the session, weighing the paper at the end of the session, and subtracting the beginning weight from the ending weight. Any fecal material adhering to other parts of the chamber at session's end were placed on the paper for weighing. Weighing was accomplished via a triple-beam balance, with weights rounded to the nearest 0.1g.
RESULTS Figure 1 shows average weight of feces deposited each day by each subject under each FT schedule and its corresponding massed-food baseline condition. Similar patterns were evident in
Subject Condition
Session Duration
B1
B2
B3
B4
Massed Food PT 30 s Massed Food PT 60 s Massed Food PT 120 s Massed Food PT 240 s
15 min 15 min 30 min 30 min 60 min 60 min 120 min 120 min
22 10 20 13 32 10 19 11
10 10 14 12 17 12 10 12
10 10 14 14 15 11 17 13
10 23 13 14 14 16 12 10
the data for three birds (B2, B3, B4). For those birds, the amount of defecation increased directly with the value of the FT. Moreover, for those birds, a greater amount of fecal material was deposited under the FT 60-s and 120-s schedule conditions than under equal-length massed-food baseline sessions. At these F1r values, standard deviations of mean grams of feces deposited during FT and control sessions did not overlap. For the fourth subject (B 1), defecation increased with FT value from PT 60- to FT 240-s, but a greater amount of feces was deposited at FT 30s than at any other schedule value. For that bird, standard deviations of mean grams of feces deposited during FT and control sessions overlapped at all FT values. Repeated measures analysis of variance was used to analyze data for the subjects as a group. There was a significant overall effect across conditions (F = 5.624, p = 0.0001). Paired t-tests, which are appropriate when few planned comparisons are of interest (5), were used to compare Fir 60-s and FT 120-s schedule group means to appropriate massed-food means. These tests revealed that the mean fecal weight for the subjects as a group significantly exceeded the massed-food baseline level at PT 60 s (t = -2.76, p = 0.009), but not at PT 120 s (t = -0.548, p = 0.587).
DISCUSSION A significant increase in defecation under FF schedule conditions relative to massed-food conditions is suggestive of schedule-induced defecation, and such an effect was evident in the present study when the P-T value was 60 s. However, even at that value, relatively little defecation occurred (i.e., the behavior was not clearly "excessive"), and it appeared that the birds emitted relatively few ( < 5) droppings per session. Schedule-induced polydipsia in rats, the prototype of adjunctive behavior, is clearly excessive and occurs after most food deliveries (3). Moreover, schedule-induced polydipsia and other adjunctive behaviors characteristically occur soon after food is consumed (3), but the temporal pattern of schedule-induced defecation in pigeons is unknown. Given these considerations, it is premature to consider schedule-induced defecation in pigeons as comparable to schedule-induced polydipsia in rats, or to other examples of adjunctive behavior. Interestingly, schedule-induced polydipsia occurs in pigeons (7,12), but it is not always observed under conditions where it is easily produced in rats (1,8,14,17). Given this, it of interest that the present study demonstrated schedule-induced defecation in pigeons under conditions roughly comparable to those that produced it previously in rats tested in our laboratory (6) and else-
DEFECATION IN PIGEONS
197
B2
B1 10-
[]
Massed-FoodDefecation
[]
P-T Defecation
7.5-
:::::: .,,o,,, .,,,-,, ..,,-,, ,,.,.,
5-
,o°.-, ,.-.,, ,.,.,, .,.°,,, .,.,,., -,-,,., .,,,,,,
m t-
2.5-
,.,,-. ,.,,,. ,,,,,. ,,,.,. .,,.,, .,,.,. .,..., -,,,-,, ,,-,-,, ,,..., ,,-,,, ,,,..-
0
!
!
!
¢*w
o
B4
B3 .$
1.5-
m
1.25 -
1"
I 0.75 i 0.5 "~
0.25 I
30
60
120
240
30
60
120
240
F i x e d - T i m e Value (sec) FIG. 1. l~[ean weight (in grams, plus one standard deviation) of feces produced by individual pigeons during the final 10 sessions of exposure to all experimental conditions. Dark bars indicate defecation when the listed fixedtime (FT) schedule of food delivery was in effect; light bars indicate defecation during the appropriate massedfood baseline for the listed FT schedule. The absence of a bar indicates no defecation. Each FT session ended after 30 food deliveries (e.g., 15 rain under FT 15 s, 120 min under FR 240 s). Massed-food sessions were equal in length to FT comparison sessions. In massed-food sessions, an amount of food (grain) approximately equal to that consumed in an ~ comparison session was presented in bulk at the beginning of the session and remained available until it was consumed, or the session ended. Note that values on the ordinate for subjects B1 and B2 are different 15aan those for subjects B3 and B4.
where (16). In those studies, as in the present one, an FT 60-s schedule induced defecal5on. In another study with rats, however, defecation was significa~atly elevated by exposure to an FT 32-s schedule, and there was no evidence that an FT 30-s schedule increased pigeons' defecation in the present study. Moreover, in
one of the four pigeons, there was no evidence of schedule-induced defecation at any FT value. Although schedule-induced defecation in pigeons appears to be real, further research is clearly required to delineate its specific characteristics and the variables that control it.
REFERENCES 1. Dale, R. H. I. Concurrent drinking by pigeons on fixed-interval reinforcement schedules. Physiol. Behav. 6:977-980; 1979. 2. Falk, J. L. Production of polydipsia in normal rats by an intermittent food schedule. Science 133:195-196;1961. 3. Falk, J. L. The nature and determinants of adjunctive behavior. Physiol. Behav. 6:577-588;1971.
4. Falk, J. L. The environmental generation of excessive behavior. In: Mule, S. J., ed. Behavior in excess: An examination of the volitional disorders. N e w York: Free Press; 1981:313337. 5. Howell, D. C. Statistical methods for psychology. Boston: Duxbury; 1987.
198
6. LeSage, M.; Makhay, M.; DeLeon, I.; Poling, A. The effects of damphetamine and diazepam on schedule-induced defecation in rats. Pharmacol. Biochem. Behav. 48:787-790;1994. 7. Magyar, R. L.; Malagodi, E. F. Measurement and development of schedule-induced drinking in pigeons. Physiol. Behav. 25:245251;1980. 8. Miller, J. S.; Gollub, L. R. Adjunctive and operant bolt-pecking in the pigeon. Psych. Record 24:203-208; 1974. 9. Rayfield, F.; Segal, M.; Goldiamond, I. Schedule-induced defecation. J. Exp. Anal. Behav. 38:19-34;1982. 10. Roper, T. J. What is meant by the term "schedule-induced," and how general is schedule induction? Anita. Learn. Behav. 9:433-440;1981. 11. Sanger, D. J. Drug taking as adjunctive behavior. In: Goldberg, S. R.; Stolerman, I. P., eds.; Behavioral analysis of drug dependence. New York: Academic Press; 1986:123-160.
JAREMA, LESAGE AND POLING
12. Shanab, M. E.; Peterson, J. L. Polydipsia in the pigeon. Psychon. Sci. 15:51-52;1969. 13. Wetherington, C. L. Is adjunctive behavior a third class of behavior? Neurosci. Biobehav. Rev. 6:329-350;1982. 14. Whalen, T. E.; Wilkie. D. M. Failure to find schedule-induced polydipsia in the pigeon. Bull. Psychon. Soc. 10:200-202;1977. 15. Wylie, A. M.; Layng, M. P.; Meyer, K. A. Schedule-induced defecation by rats during ratio and interval schedules of food reinforcement. J. Exp. Anal. Behav. 60:611-620;1993. 16. Wylie, A. M.; Springis, R.; Johnson, K. S. Schedule-induced defecation:No-food and massed-food baselines. J. Exp. Anal. Behav. 58:389-397;1992. 17. Yobum, B. C.; Cohen, P. S. Assessment of attack and drinking in White King on response-independent food schedules. J. Exp. Anal. Behav. 31:91-101;1979.