Transformation of a waiting schedule into a temporal regulation schedule (DRRD) by addition of external stimuli in the dog

Behaviourd

Processes,

17 (1988) 117-129

117

Elsevier

TRANSFORMATION OF REGULATION SCHEDULE THE DOG

A WAITING SCHEDULE INTO A (DRRD) BY ADDITION OF EXTERNAL

BRUHWYLER,J., CHLEIDE,E., GUEURH. and MERCIER,M.’ Department of Psychology, Faculty of Medicine, F.N.D.P., 5000 Namur, BELGIUM (Accepted

5 July

TEMPORAL STIMULI IN

61 rue de Bruxelles,

1988)

ABSTRACT Bruhwyler,J., Chleide,E., Gueur,H. and Mercier,M. 1988. Transformation of a waiting schedule into a temporal regulation schedule (DRRD) by addition of 17: 117-129 external stimuli in the dog. ixehav. PROCESS.

Waiting schedules do not impose temporal regulation but condition the At the end of the animal to give the operant response during a given time. a positive discriminatrve stimulus is presented. The required delay, suspension of the response while the discriminative stimulus is being given is accompanied by rernforcement. The transformation of a waiting schedule enerally achieved by suppressing the into a temporal regulation schedule is p 1 ysically modifying them. Our study external facilitating factors or by reveals that a similar transformation can be achieved In the dog by the addition of a further stimulus. This stimulus, which is physically exactly the same as the excitatory stimulus and which punctuates the waihng period, is randomly introduced into the temporal delay. The absence of reinforcement in response to the added stimulus should force the animal to regulate its behaviour in time and the additional negative discriminative stimulus favours the expression of the active nature of the inhibition. The results show that subjects can differentiate their response durations according to stimuli that onl differ according to temporal location. Thus this pattern resembles a DRLD schedule. The peak of res onses at the time of the inhibition stimulus reveals considerable behavioura P conflict : either the response must be maintained or the inhibition suppressed. The positive or negative resolution of this conflict reveals noteworthy aspects of the behavroural inhibition process. Key words : Temporal regulation, waiting schedule, inhibition, dog, external cues INTRODUCTION The conditioning

study of the mechanisms with schedules temporal

according ‘Authors are presented line with the thesis of Gueur,H. : dans un mod&e d’inhibition et @.miliariS”, under the supervision of

0376-6357/88/$03.50

0

1988 Elsevier

of

conditioned components

inhibition,operant particulary are

to alphabetical order. This research is in comportementaux de psychotropes de regulation temporelle chez Ca nis Giurgea,C. and Mercier,M.

” Effets

Science

Publishers

B.V. (Biomedical

Division)

118

interesting. In fact time-regulated behaviour implies a process whereby a response is not simply absent for a given period but is delayed during that time (Richelle, 1972). Among these operant procedures, the DRL (Differential Reinforcement of Low rates of response) reinforces a response only if a fixed minimum delay has elapsed since the previous response, whether reinforced or not (Ferster and Skinner, 1957). This contingency necessitates the total absence of responses during the required delay. By imposing temporal regulation, the DRL also obliges the subject not to respond during a certain time, making motor inhibition compulsory (Macar, 1980). The task can be made even more specific by fixing an upper limit (Limited Hold = LH) beyond which the subject cannot go. Among the schedules derived from the DRL, the DRRD (Differential Reinforcement of Response Duration) requires the maintenance of an operant response for a fixed period to obtain reinforcement. The animal itself initiates the delays, the response being reinforced only if it is maintained for a minimum fixed period. An upper temporal limit can also be added (DRRD LH) (Richelle and Lejeune, 1980; Lejeune and Jasselette, 1987). By imposing temporal regulation, these schedules also inhibit behaviour which is incompatible with the maintenance of the operant response. According to Macar (1979), the time factor is not simply reduced to a measurement of duration but acts as an inhibitory regulator of the action. not imposing temporal regulation, Waiting schedules, although condition the animal to produce a response for a fixed period of time. In Blough (1958), this response consists in the pigeon not moving its head during the waiting period. At the end of the required delay, a discriminative stimulus is given. The withholding of the response while this discriminative stimulus is being given is accompanied by reinforcement. involving internal temporal Numerous experimental schedules, components, have in addition involved external synchronizers in different forms. Sometimes it is a spatial stimulus which is increased or moved about in relation to time (Ferster and Skinner, 1957; Ferster and Zimmerman, it is an auditory stimulus which is made 1963),in other experiments, increasingly intense (Ferster and Zimmerman, 1963; Marcucella, 1974); it may even be a sequence of intermittent sound signals (Macar, 1971) or a succession of visual stimuli of different colours and shapes (Segal, 1962; Laties and Weiss, 1966; Auge, 1977). In all these cases, the external supports of duration clearly assist the subject in its regulation or its temporal estimation (Macar, 1979). The external signals increase the probability of correct responses when this is already high (Macar, 1969). The facilitating role of the external stimulus appears most clearly when it periodically punctuates the action (Lejeune, 1978). The elimination of this external information, as in the studies by Macar (1969, 1971), Deliege (1975) and Lejeune (1978), results in a serious drop in the level of performance. However, it seems that this signal only

plays an auxiliary role since, even with its suppression, a detectable regulation remains , though weaker than that which existed previously. This is particularly clear in the case of intermittent signals. Macar (1969) has shown that : “If the delay of 40 seconds which must separate response A from response B is punctuated by 3 auditory signals of 10 seconds each, the cat gives a performance which is markedly superior to that given in the absence of signals. The animal clearly has very little difficulty in counting three successive events. This will be seen by reducing the interval between the signals; the subject will then reduce the intervals between its responses. However, their bimodal distribution will testify to the simultaneous control, which has now been dissociated, of the external signal, on the one hand, and of duration, on the other”. The transformation of a waiting schedule into a schedule of pure temporal regulation (like DRL or DRRD) can be achieved either by taking external synchronizers away or by changing their value. In this context, pure temporal regulation means correct positioning of actions in time without external synchronizers. Thereafter, whereas the waiting schedule would only lead to a spontaneous temporal regulation, the DRRD imposes it and makes it a condition for obtaining reinforcement. This imposed temporal regulation is called acquired temporal regulation (Fraisse et al., 1979). We introduced into the model of Kupalov, as described by Giurgea in 1974, a transformation of the same type by inserting, randomly from one trial to the other, the same discriminative stimulus into the waiting interval as that used to end the waiting interval. In accordance with the theories of conditioned inhibition (Boakes and Halliday, 1972; Miller and Spear, 1985), our hypothesis is that the absence of reinforcement in response to this added stimulus must oblige the animal to temporally regulate its behaviour. According to Hearst (1972) conditioned inhibition develops from a training procedure that involves some negative relationship between the presentation of an external stimulus and subsequent occurrences of another event or outcome, namely the reinforcement. Indeed, the random presence of this added stimulus in the time delay prevents the animal from making a simple count of two exteroceptive events. Therefore, since these two stimuli are identical from a physical point of view, the animal can only discriminate them by their temporal positioning during and at the end of the delay. Moreover, these two stimuli should have different meanings and functions in relation to inhibition, solely on account of their temporal location, the supplementary discriminative stimulus favouring the expression of the active nature of inhibition. Indeed, adjusting to or estimating duration for an organism is not simply putting landmarks in the flow of time, it means retaining and deferring action (Richelle and Lejeune, 1980). Given the methodological impossibility of directly measuring the central inhibition, temporal regulation, when controlled by conditioning, can be considered as a behavioural indication suitable for revealing the existence of a regulation that inhibits action (Richelle and Lejeune, 1980).

120

MATERIAL AND METHOD - Subjects : Five one-year-old male dogs of Beagle breed weighing from 11 to 14 Kg were used In these experiments. Animals were kept in an animal house, in se arate cages. They were fed daily at the end of the day with whole food (0 ervo Expan) (250 g). - Test-room (fig 1) : The size of the test-room was 5.6 x 3.4 m. At the entrance, in the right-hand corner there was a board (60 x 50 x 2 cm) round. In the opposite corner, at the end of the room! lays the fastened to the window 80 food dispenser 950 x 76 x 52 cm). The end wall had a full-width cm from the ground which opened onto the outside. The auditory signals for the tests were emitted from two loud-speakers incorporated in the ceiling. Water was available throughout the sessions. During the experimental sessions, the experimenter stood in an observation booth fitted with two-way mirrors. The booth contained all the controls of the external stimuli, the distribution of reinforcements as well as the material for observing and recording the sessions. -Conditionin procedure : Experimental sessions took place every day, they were limite rY by the subject obtaining all its 8 reinforcements and/or by a maximum time of 900 sec. The reinforcement consisted of a small meat sausage (5 g). A. Shaping

: Shaping

fell into 3 stages.

1st stage : During the 1st stage, the dog was free to explore the room durin a maximum time of 900 sec. If by chance the food dispenser was operate c?, the sub’ect was ,reinforced. A first, baseline was reached after 10 sessions, \;J,aense;(I the mdrviduals had received the 8 reinforcements within the given 2nd stage : During the 2nd stage, the dog had to walk across the board and straightaway jump onto the dispenser to get the reinforcement. Afterwards the contingencies of a waiting schedule came into lay : the behavior of remaining one second on the board was followed g y a positive auditory stimulus (click) (CS+) as the dog moved from the board to the dispenser. After 10 sessions, a second baseline was reached for the 5 subjects when 8 reinforcements were obtained within the given 150 seconds. 3rd stage : During this 3rd stage, the waiting time delay re uired on the board er was progressively raised to 9 set at the rate of one ad a.rtronal second session. Each trial ended with the CS+ bein given for 1.5 sec. R ny immediate1 withdrawal from the board in response to t?l at stimulus, followed by a jump onto the dispenser, was reinforced. On the other han dy withdrawals for durations inferior to 9 set or suoerior to 9 set + LH = 10.5 set were penalized by no reinforcement being given. Any false response reinitialized the time and the trial. A stable performance was obtained for the 5 subjects within the given 20 sessions. B. Final

procedure

(fig 2)

The final procedure consisted in the random alternation of 2 kinds of trials. The first kind of trial was the one previously described in the waiting schedule, i.e. a locomotor restriction on the board for 9 set followed by the CS+ (LH 1.5 set) and b a jump onto the dispenser . The second kind of trial differed from the first i y the random addition of the same auditory stimulus between the 3rd and the 6th set of the delay. Both auditory stimuli, presented between 3 and 6 set and at 9 set were strictly identical from a physical point of view and had the same duration (1.5 set); the animal could only discriminate between them according to their location in time. Both kinds of

121

I

,

OB : observation booth C : container (water) E : entrance D : distributor PL : plank FC : fastened camera

L

d

i

Fig 1. Test room -

0

3-

: I

6------9

i

I

lo.5

: , I

TIHfz (s=)

NR : Non-reinforced responses R : Reinforced responses S+ : Positive discriminative stimulus S- : Negative discriminative stimulus DX : Early response before any stimulus DY : Early response with regard to S DZ : Early response between S- and S+ DO : Late response beyond imposed time delay Fig 2. Final schedule : S from 3 to 6 set and S+ at 9 set

122

trials were distributed randomly during the session. Thus, the added stimulus was doubly random, first, because it was not iven on each trial and secondly, because it was given at random between 3 an c?S sec. In all the cases, the only reinforced response was the response to stimulus at 9 set, any premature (c 9 set) or late (> 10.5 set) response not being reinforced. Parameters

: The parameters

which

were

considered

during

a session

were

:

- percentage of reinforced responses - types of errors : - DX : early withholding of the

response before any stimulus was iven (before the positive stimulus in the first type of trial and before t?l e negative one In the second type of trial). - DY : early response to the discriminative negative stimulus (not reinforced between 3 and 6 set). - DZ : early response between the discriminative negative stimulus ositive stimulus (reinforced). (not reinforced) and the discriminative - DO : late response beyond the imposed 8 elay (9 set + LH 1.5 set). - tern oral distribution of response durations - tota P rate of responses/min - rate of correct responseslmin Processin? Student’s

The statistical analysis test by paired observations.

of

the

results

was

obtained

from

RESULTS - Shaping : The evolution of the temporal distribution of the response durations during the learning of the waiting schedule until the final step, of 9 set is shown In fig 3. The dynamics of this learnin sessions), only 3 sta es were presented (3 set + CS+ L 19 lb:i:KrY,,r,ap,ldc$9+ LH 1.5 set, 9 set + CgS+ LH 1.5 set). For a waiting time of 3, 6 or 9 set (fig 3A to 3C) followed by the presentation of the positive discriminative stimulus, the only errors noted (40%. 50%, 30% respectively) were anticipated ones of the DX type. No error of the DO type was recorded. - Final

procedure

A. Evolution of the response rates No significant change in the response rates was noted in the learning as a whole of the final procedure (frg 4). Nevertheless, a more detailed analysis showed a reduction in the rate of correct responses (P-=0.01 for sessrons 1 and 3, PcO.05 for session 10). Once the performance stabilized, the differences between the response rates with regard to the initial waiting schedule became insignificant (P>O.O5). of response durations. B. Quantitative anal sis of the tern oral distribution of the initial waiting Fig 5 (A-$) illustrates t Ee transformation schedule by introducrng the negative (not reinforced) discriminative stimulus between the 3rd and the 6th set of the delay. From the first session onwards this transformation resulted in the change from a ,unimodal distribution centred on 9 set, to a bimodal cI$.ribution for which the second mode was centred on the interval of 3 to 6 This second mode could be made up both of DX errors and erroneous During the 3rd responses to the ne ative discriminative stimulus (DY). this bimoda 9,rty was maintained with a greater shift of responses session,

123

Reinforced responses Non-reinforced responses

01

234 Fig 3.

A o * **

= = = =

56

79

9

‘IME (SEC 1

Evolution of temporal distribution of responses (R) for the waiting schedules with auditory stimulus at 3 set (3A), at 6 set (3B) and at 9 set (3C)

Correct response rates Total response rates PCO.5 Pco.01 (Comparison between the sessions procedure and the waiting schedule)

of the final

Fig 4. Evolution of the response rates per minute for the transition from the waiting schedule to the final schedule until a stabilized performance is obtained (30 th session)

124

60 a0

Fig 5A. Waiting

schedule

Fig 58. Session

1

Fig 5C. Session

3

Fig 5D. Session

10

i

-/n.A.

80

Fig 5E. Stabilized perf. (30th session)

60 40 20 0 !+LJ!L

0113r567880

l2-

,t; J

rmfs(SK

1

m = Non-reinforced esponses o = Reinforced responses Fig 5. Evolution of temporal distribution of responses at the transition from the waiting schedule (Fig 5A) to the final schedule : from session 1 to stabilized performance. (Fig 5B to 5E)

towards balanced sessions

As re,aards the 10th session,, fi$.a;ir s&owds,; 3-6 set (fig. 5C bimodality of w b ich stab1 rzed performance obtaine then shifts in favour of the responses centred on 9 set (fig. 5E).

C. Quantitative analysis of types of errors (table 1) The change from waiting schedule to final schedule was characterized by a clear deterioration in performance with an increasing percentage of This increase was principally due to 3 new types of errors : DY errors. (response to the negative discriminative stimulus), DZ (response between the ne ative discriminatrve stimulus and the positive discriminative stimulus) an 3 DO (response beyond 10.5 set). This deterioration was even more obvious for the third session with an additional increase in the DY (P<‘O.O5) and a very weak reduction in the DO (P < 0.01). sEss1oN 3 -10

SESSION l-3 b

OX Dv

-02 +14.9

2.3 12.3

02 Do

-1.9 -2 1

2.9 1.1

D

t

s

0.20 271 I .46 4.23

NS S NS 93

NS (P>O.l), S D = Average S = Standard t = Student’s

l0.4 -24.5 -0.7 l0.07

t

s

2.0 17.6 1.6 0.4

SESSION 10-dmB.

0.45 3.08 0.87 0.40

5s

16 9 Is IIs

PmF. t

- I.6

0.9

4.47

-7.2 -0.6 qo.03

9.7 1.6 0.3

1.66 = 0.84 1Is 0.22 Is

(P
ss

in pairs

Table 1. Comparison of the types of errors for the final schedule, between session 1 and 3, session 3 and 10, and between session 10 and a session with stabilized performance

The percentage of errors then dropped through a reduction of DY PcO.05 When the erformance stabilized, after 30 sessions, DY type errors [P>O.OSj’as well as 8 X (P
126

temporal delay. During the first learning session a high percentage of responses is recorded for this stimulus (rate of errors increases significantly). This observation concurs with the results of Contrucci et al. (1971) who note a considerable increase in responses when a stimulus is added in the interval of a DRL. According to them, this phenomenon can be explained by a disinhibition of the response. Disinhibition might be defined as the temporary reappearance of a suppressed or inhibited conditioned response due to the presentation of an extraneous stimulus (Brimer, 1972). After some training sessions, the bimodality of responses, centered on the errors, shifts in favour of the correct responses (rate of correct responses increases significantly). This can be explained by the weakness of the disinhibitor characteristic of the added stimulus due to the absence of reinforcement for the responses produced (Contrucci et al., 1971). The temporal distribution of the response durations derived from the stabilized performance shows that subjects adapt to the interval of 9 set (% correct responses = 75 %). The reduction in the percentage of responses to the negative stimulus testifies to the inhibitory control exerted by that stimulus on the behaviour. This is in complete agreement with the conclusions of Jenkins (1965), according to which a stimulus exerts an inhibitory control in so far as it acts as a signal for the non-response. The fact that a high percentage of errors persists (25 %) reflects the complexity ot the required task at the behavioural level. Indeed, in order to discriminate the two stimuli given in doubly random fashion in the delay, the dog can only rely on their location in time. The fact that the subjects succeed in differentiating their responses according to stimuli which only differ in their temporal location makes the pattern we use quite similar to a DRRD (Differential Reinforcement of Response Duration) (Richelle and Lejeune, 1987). According to Kuch (1974) : “The 1980, Lejeune and Jasselette, differentiation of the response is a special case of discrimination of stimuli, in which the stimuli to be discriminated are correlated with a parameter of the response : its duration”. Together with several authors (Logan, 1961; Zimmerman, 1961; Molliver, 1963; Macar, 1969; Blackman, 1970; Catania, 1970; Cohen, 1970; Schwartz and Williams, 1971; Platt et al., 1973; Lince, 1976; Greenwood, 1978), we do not observe bursts of responses in the brief inter-response intervals. In the present instance, this absence could be explained by the important control exercised by the stimuli on the responses. The animal rarely takes the initiative to respond before the first stimulus is presented since in all the cases the reinforcements are granted following an external stimulation. The presence of inhibitory and excitatory external components makes this pattern different from a conventional DRRD. This difference explains the peak of responses that persists between 3 and 6 sec. In fact the discriminative stimulus at this moment presentation of the negative provokes an important conflict between two responses : either the motor inhibition is maintained or it is released and the subject leaves the board.

127

This conflict can only be resolved in a valid way by discrimination on the part of the subject in respect of the duration of its responses. Thus we confirm the main hypothesis of Richelle and Lejeune (1980) according to which the conditioning schedules are relevant indications suitable for revealing the existence of an inhibitory regulation of the action. ACKNOWLEDGMENT We would like to thank Dr. C. GIURGEA for his advice and for the revision our manuscript and Dr. KELLY for assisting in the translation of this text.

of

REFERENCES Auge,

R.J., 1977. Stimulus functions within a fixed-interval clock unishment and discriminative stimulus schedule: reinforcement, control. Animal Learning an 8 Behavior., 9: 1!7-123. Bacotti, A.V., 1981. aCrloddzaprneeffects on respondrn maintained under shock resentation shock termrnatron SCR edules. Pharmacology g.rochemistrv and Behavior.. 15 : 415418. Blackman, D.E.,’ 1970. Effects’ of pre-shocks stimulus on temporal control of behavior. Journal of the Exoerimental Analvsis of Behavior., 14:313-319. Blough, D.S., 1958. New test for tran uillizers. Science., 127: 586-587. Boakes, R.A. and Halliday, M.S., 19972. Inhibition and Learning. Academic Press. New York. Brimer, C.J., 1972. Disinhibition of an operant response. b: Inhibition and Learning. Boakes and Hallida s(Eds.), Academic Press, 205-227. Canon,. J.G. and Lippa, A.S,, 197 7y(a). Effects of clozapine, chlorpromazine and drazepam upon adjunctive and schedule controlled behaviors. Biochemistr and Behavior., 6 : 581-587. Cano~h”JrG”ac$“dg~ippa A.S Y977(b C Use of DRL in differentiating anxiolytic and neuroleptrc properiies of NS drugs., Pharmacology Biochemistry and Behavior., 6 : 591-593. Canon, J.G.. 1979. A comoarison of clozaoine. chlororomazine and thioridazine ~ w ., ’ performance in the s~,rr,el~ monkey. Psycho harmac%yiny if? 5 -60. Catania, A. 1970 einforcement schedules and psycholo rhal udgment:a study oi’ some temporal properties of behavior. In: choenfeld Editor), The Theory of Reinforcement Schedule, Prentice Hall, Inc. L nalewood Cliffs. New Jersev. l-42. Cohen, P.S., 1970. DRL escape:-‘effects of minimum duration and intensity of electric shock. Journal of the Exoerimental Analvsis of Behavior., 13: 41-50. Contrucci, J.J:, Hothersall, D. and Wickens, D.D., 1971. The effects of a novel strmulus introduced into a DRL schedule at two temporal placements. Ps chonomic Science., 23 (1B): 97-99. Deli& e, M., 197 5 . Le Comportement de Regulation Temporelle en B rogramme a lntervalle Fixe. University of Liege, Unpublished doctoral dissertation. Ferster, C.B. and Skinner, B.F., 1957. Schedules of Reinforcement. Appleton Century Crofts, New York.

128

Ferster, C.B. and Zimmerman, J., 1963. Fixed-interval performance with added stimuli in monkeys. Journal of the Experimental Analysis of Behavior., 6: 317-322. Fontaine, 0. and Richelle,, M., 1969. Etude comparative chez le rat des effets de la chlorpromazrne et du chloridazepoxide sur une serie de rogrammes a renforcement positif et a renforcement negatif. Montangero, J., Nuttin, J. au Temps Psychologique., Giurgea, C., 1974. The creative world of P.S. Kupalov. Pavlovian Journal of Biological Sciences., 9 (4): 192-207 Greenwood, P., 1977. Contribution a I’Etude pes Regulations Temporelles Acquises chez le Chat (Felis domest casl. University of Liege., Unpublished Master Thesis. Greenwood, P., 1978. Fietroregulation proprioceptive et regulation tern orelle acquise chez le chat. C.R. Sot. Biol., 172: 1013-1016. roblems in the analysis of conditioned Hearst, g. 1972. Some persistent inhibiiion. In: Inhibition and Learning, Boakes and Halliday (Eds.), Academic Press, 5-39. Jenkins, H.M., 1965. Generalization gradients and the concept of inhibition. In: D. Mostofsky (Editor), Stimulus Generalization. Stanford University Press, pp 55-61. Kuch, D.O., 1974. Differentiation of press durations with upper and lower limits on reinforced values. Journal of the Experimental Analysis of Behavior., 22: 275283. Kupalov, P.S. 1983. Situational Conditional Reflexes: physiolo ic studies of moving animals., Pavlovian Journal the hi her nervous activit of free1 of Bio?ogical Sciences. ll (1): l3-ll. Laties, V.G. and Weiss, B.: 1966. Influence of drugs on behavior controlled The Journal of Pharmacology and by internal and external stimuli., Experimental Therapeutics., 152: 388-396. Lejeune, H., 1978. Sur un paradoxe dans I’estimation du temps chez I’animal. L’Annee Psychologique., 78: 163-181. 1987. Differential reinforcement of Lejeune, H. and Jasselette, P., response duration (DRRD) in weanling rats: a comparison with adult sub’ects. Behavioural Processes., 15: 315-332. Lince, 1976. Activite Collaterate et Regulation Temporelle en DRL. University of Liege. Unpublished Master Thesis. Logan, F.A., 1961. Discrete-trials DRL., Journal of the Experimental Anal s/s of Behavior., 4:277-279. Macar, f? 1969. Etudes de Quelques Problemes dans le Cadre des Regulations Temporelles Acquises. University of Liege. Unpublished Master Thesis. Macar, F.,,, 1971. Addition d’une horloge externe dans un programme de condmonnement au temps chez le chat. Journal de Psychologie Normale et Patholo ique., 1: 89-100. Macar, F., 197 &t. Relations entre les variations lentes de potentiel cortical et

d.

Presses

Universitaires

de

France,

Marcucella, H.,, 1974. Signalled reinforcement in DRL schedules. Journal of the Experimental Anal si; of Behavtor., 22:.381-390. h 1985. lnformatron Processing in Animals: Miller, R.R. and Spear, Conditioned Inhibition. Hillsdale N.J.: Erlbaum. Molliver, M.E., 1963. Operant control of vocal behavior in the cat. Journal of

129

the Ex erimental Analysis of Behavior., 6: 197-202. durations as J.R., R uch, D.O. and Bitgood, S.C., 1973. Rats’ leverpress psychophysical judgments of time. Journal of the Experimental Analysis of Behavior., 19: 239-250. Richelle, M., 1969. Combined action of diazepam and d-amphetamine on fixed-interval performance in cats. Journal of the Experimental Analysis of Behaviour. 12 : 989-998. Richelle, M., 1972. Temporal re ulation of behaviour and inhibition. In: Boakes, R.A. and Halliday, M!.S (Editors), Inhibition and Learning, New York, Pergamon Press, 229-251. Richelle, M., 1978. Action des benzodiazepines sur le comportement acquis chez I’animal. Psycholo ie Medicale., 10(A) hors serie : 95108. Richelle, M. and Le’eune, 1980. Time in Animal Behaviour. Pergamon Press, Oxford, ew York. Salmon, P. and Gray, J.A,, 1985. Comparison between the effects of ropanolol and chlordrazepoxide on timing behaviour in the rat. F sychopharmacology., 87 : 219-224. Sanger, D.J. and Blackman, D.E., 1976. Rate-dependent effects of drugs : a review of the literature. Pharmacology Biochemistry and Behavior., 4 : 73-83. on timing behaviour in rodents : Sanger, D.J., 1980. The effects of caffeine comparisons with chlordiazepoxide. Psychopharmacology., 68 : 305-309. Schwartz, B. and Williams, D.R., 1971. Discrete-trials spaced responding in the pigeon: the dependence of efficient performance on the availabitity of a stimulus for collateral pecking. Journal of the Experimental Anaz;s of Behavior., 16: 155-l 60. 1962. Exteroceptrve control of fixed-interval responding. Segal, Journal ‘of the Experimental Analysis of Behavior., 5: 49-57. Zimmerman, J., 1961. Spaced respondin in rats as a function of some Analysis of Behavior., tern oral variables. Journal of the Egxperimental 4: g 19-224.

Platt,

J

it..