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Timeout from a stimulus correlated with the extinction component of a multiple schedule
LEARNING
Timeout
AND
MOTIVATION
from
4, 294-304
( 1973)
a Stimulus
Component
Correlated
of a Multiple
RICHARD Fairleigh
C.
COUGHLIN,
Dickinson
with
the
Extinction
Schedule1 JR.
University
Four groups of pigeons were trained to discriminate between green and red. Pecks on a second key produced a timeout from the schedule in effect for 30 sec. For two of the groups, this timeout response turned off all the lights in the chamber (Blackout), while for the other two, only the keylights were turned off (No Blackout). For one of the Blackout groups and one of the No Blackout groups, responses on the discrimination key during the extinction component (S-) also resulted in a mild electric shock. Blackout groups produced more timeouts during S- than did No Blackout groups, but electric shock punishment suppressed, rather than enhanced, timeout responding. These findings suggest a need for reevaluation of the hypothesis that the timeout response is an escape from an aversive S-.
Researchers in the field of discrimination learning have often made the assumption that the stimulus correlated with the extinction component (S-) of a successive discrimination is an aversive stimulus (Amsel, 1962). Evidence for this notion, however, has been largely indirect. Terrace (1966), for example, suggested that the occurrence of behavioral contrast (Reynolds, 1961) and the peak shift (Hanson, 1959) could be indicative that successive discrimination training has resulted in an aversive S-. Recently, a more direct measure of the aversive properties of S- has been proposed. Using an escape paradigm, Rilling, Askew, Ahlskog, and Kramer (1969) demonstrated that pigeons in a successive discrimination situation would peck a second key in the presence of the S-, if that response produced a SO-set blackout of the chamber. They suggested that S-, in this situation, functioned as a conditioned aversive stimulus from which the birds escaped by making the timeout response. These findings have been substantiated and extended by Rilling, Kramer, and Richards ( 1973) and Terrace ( 1971) . I This research was conducted while the author was supported by a National Dcfense Education Act, Title IV, Predoctoral Fellowship. It is based, in part, on a dissertation submitted to the Graduate College of the University of Vermont in partial fulfillment of the requirements for the Ph.D. degree. Bequests for reprints should be sent to the author, Department of Psychology, Fairleigh Dickinson University, Madison, New Jersey 07940. Copyright All rights
294 @ 1973 by Academic Press, Inc. of reproduction in any form reserved.
TIMEOUT
FROM
S-
295
Coughlin (1970a) also attempted to replicate the findings of Rilling et al. ( 1969), but was unable to find sustained timeout responding during S- when the effects of stimulus change were controlled. In that study, when the timeout response merely removed the key lights, and not the other chamber illumination, timeout responding had ceased for most birds by the tenth session. When the contingency on the timeout key was changed, so that responses produced a total blackout of the chamber, responding reoccurred and was maintained at a high level. It is possible, therefore, that the findings of Rilling and his associates (Rilling et al., 1969, 1973) could be explained in terms of stimulus change reinforcement, rather than in terms of the aversive properties of S-. The findings of Terrace (1971) contradict that conclusion. He used a control for the effects of stimulus change similar to Coughlin (1970a), such that the timeout response only removed the S- keylight. He also ran a control group, for which a response on the timeout key could turn out the timeout keylight, but not the S- keylight or the houselights. Birds in the control group stopped responding quickly, and although the timeout responding of the experimental group declined appreciably during the 15 days of discrimination training, it appeared that the pigeons were still responding. In the Coughlin (1970a) study, however, seven of the 18 birds had ceased responding within 5 days. In light of this apparent contradiction the present study was designed to further examine the role of stimulus change. The contingencies on the timeout key were varied so that for some of the birds, a response on the timeout key produced a blackout, while for the remainder, a response only removed the keylights. This enabled a direct comparison of the effects of the blackout in producing and maintaining the timeout behavior in S-. Whatever the role of stimulus change, it remained to be demonstrated conclusively that the timeout response is an escape response from an aversive stimulus. Crucial to Terrace’s (1966) argument that S- is aversive, are the studies of Brethower and Reynolds (1962) and Grusec (1968). In the former study, it was shown that punishing responses in one component of a multiple schedule resulted in an increase in response rate in the other component. Grusec ( 196S), moreover, showed that noncontingent electric shock in S- either produced or enhanced the peak shift-depending on whether the discrimination had been learned without or with errors, respectively. These studies suggest that the addition of electric shock should be one way of increasing the aversiveness of the S- stimulus. Therefore, this study also looked at the effects of punishing S- responses on timeout behavior. It was hypothesized that punishing re-
296
RICHARD
C.
COUGHLIN,
JR.
sponding in S- with mild electric shock should make the Sthan if it was merely correlated with extinction. If this is the timeout response is really an escape response from an ulus, birds in the shock groups should make more timeout
more aversive the case, and aversive stimresponses.
METHOD
Subjects. The subjects for this experiment were 48 male White Carneaux pigeons, obtained from the Palmetto Pigeon Plant, Sumter, South Carolina. They ranged from 6 mo to 1 yr in age, and were maintained at 80% of their free-feeding body weight for the duration of the experiment. Water was always available in the home cages. Apparatus. Three standard three-key pigeon chambers (Lehigh Valley Electronics, model 1519) were used in this experiment. Either a red or a green light illuminated the center key, while the right-hand key was illuminated with an amber light. Since the left-hand key was not used in this experiment, it was covered with electrical tape. There were two additional sources of illumination in the chamber: a front houselight (2.8 W) located over the center key, and a rear houselight ( 1.12 W) mounted on the opposite wall. Reinforcement was 3-set access to the grain magazine containing a mixture of 50% Kalfir, 40% Vetch, and 10% Hempseed. The experiment was programmed by means of appropriate clocks, counters, and relay circuitry, located in a room adjacent to the experimental room. The shock source was ac line voltage controlled by a variable step-down transformer, connected in series with the subject through a lO,OOO-ohm resistor. Design. Four groups of subjects (?a = 12) were run, using a 2 X 2 factorial design. During the 20 sessions of Phase 1 (prediscrimination training), all birds were treated identically, except for the contingency correlated with the timeout key ( Blackout vs No Blackout). Thus half the birds could produce a blackout by pecking at the amber side key while the other half could only turn off the keylights. On day 21, Phase 2 began and lasted for 15 sessions. In this phase, the groups were further differentiated, this time in terms of the contingencies on the center key during red (S-). For half of the Blackout birds and half of the No Blackout birds the S- key was correlated both with Extinction and with a brief l-mA electric shock for each response on the red key. For the remaining birds, S- was correlated only with Extinction. This design, in terms of the groups and the contingencies on the response keys, is outlined in Table I. Procedure. All pigeons were fitted into a harness (Azrin, 1959) which was connected at one end to l&gauge stainless steel electrodes implanted around the pubis bones (Coughlin, I97Ob). During the experimental sessions this harness was connected to a retractile cable running to the
TIMEOUT
FROM
TABLE Experimental
297
S-
1 Design Response key
Group
Amber Side keya
Green Center key (S+)
Red Center key (S-)
Phase 1 (20 sessions) Response contingency B-S B-NS NB-S NB-NS
Blackout,
VI Wsec
VI 3O-set
No Blackout”
VI 30-set
VI 30-set -
Phase 2 (15 sessions)
-
Response contingency B-S B-NS NB-S NB-NS
Blackout Blackout, No Blackout* No Blackout*
VI VI VI VI
30-set 30-set 30-set 30-set
EXT EXT EXT EXT
a Amber side key illuminated when either red or green is illuminated Response removed schedule in effect for 30 sec. * Key lights turned off-rear houselight remained on. c l-mA shock delivered only if response is made.
19 Shock only & Shock only on center key.
shock source via a freely turning telephone jack located in the ceiling of the chamber. After the pecking response had been conditioned to the green center key, responses on that key were reinforced on a variable-interval 30-set (VI 30-set) schedule. Red and green key lights on the center key were both correlated with reinforcement and were presented alternately. Each stimulus presentation lasted 4 min during which time, the rear houselight was also illuminated. Between each stimulus component, the rear houselight and the keylights were turned off and the front houselight was turned on for 5 sec. The session was terminated after each component had been presented five times. Thus, a session lasted about 40 min. In the first session of VI training, the right-hand side key was illuminated with an amber light. A peck on this key resulted in a 30-set timeout during which time pecks on the keys had no effect. This timeout response either blacked out the entire chamber, or merely turned off the key lights, depending on the group to which a bird had been assigned (see Table 1). At the end of this timeout, the contingencies on the keys were reinstated. The timer controlling the duration of the center-key
298
RICHARD
C.
COUGHLIN,
JR.
component continued to run during the timeout, even though the tapes controlling reinforcement did not. If a timeout occurred when there was less than 30 set remaining for the center-key component, the timeout was terminated by the onset of the 5-set interstimulus interval. Phase 2 began in the session immediately following the 20 daily sessions of Phase 1. During this phase, the red key was correlated with an extinction (EXT) schedule; green continued to be correlated with the VI 30-set schedule. For the birds in the Shock groups (B-S and NB-S) each response to the red key also resulted in a brief (40 msec), 1-mA electric shock. To ensure that the birds in the No Shock groups (B-NS and NB-NS), whose harnesses were also connected to the ceiling jack, would not accidently receive shock, the shock source was disconnected outside the chamber during their sessions. Phase 2 lasted for 15 sessions. Each session ran for about 80 min, and was terminated after each center-key component had been presented 10 times. The birds were run in two replications, with half the birds in each group being run in each replication. RESULTS
Center-Key Responding S-. In order to assesswhether delivering electric shock, contingent on responsesto the S- key, made that stimulus more aversive, a punishment definition of an aversive stimulus was used (Coughlin, 1972). That is, the more suppression that occurs in the presence of a stimulus, the more aversive that stimulus is. Thus, suppression ratios were computed for responding to S-. The baseline was determined by taking the average rate of response to the red key for the last five sessionsof Phase 1 for each bird. This was divided into the response rate of each bird in each session of Phase 2, adjusted for the amount of time actually spent in S-. In other words, since a timeout response reduced the amount of S- time in which further responses to the red key could be made, the rate measure was based only on the time during which the keylights were illuminated. Figure 1 shows the suppression ratios for each of the groups over the 15 sessionsof discrimination training (Phase 2). As can be seen the two Shock groups (B-S & NB-S) suppressed more quickly than the two No Shock groups (B-NS & NB-NS). This difference tended to disappear for the Blackout groups, but for the NO Blackout groups, shock continued to suppress S- responding more than extinction alone. An analysis of variante on these data revealed that the Shock effect was significant, F( 1,44) = 57.92, p < .OOl. There was also a significant Shock x Blackout interaction, F(1,44) = 4.79, p < .05.
TIMEOUT
FROM
299
S-
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IESSION
FIG. 1. Mean sessions
of Phase
suppression 2.
ratios
for
center
key
responding
in
S- during
the
15
S+. The response rate on the center key during S+ was converted to a ratio similar to that used for the S- data-a contrast ratio, in which a baseline response rate was divided into the daily response rate for Phase 2. Thus, if a bird responded at a rate of 60 responsesper min, as compared to a baseline rate of 40 per min, the ratio for that day would be 1.50. This allowed for direct comparison of the changes in S+ rate for all groups. Through the fourth session, the groups all showed about the same amount of contrast, as can be seen in Fig. 2. After that session,the curves for the Shock groups separated from those of the No Shock groups. In other words, the No Shock groups showed more behavioral contrast than the Shock groups. An analysis of variance on the contrast ratios revealed that the Shock effect failed to reach significance, F( 1,44) = 3.78, p > .05. There was, however, a significant Shock x Session interaction, F( 14,616) = 2.30, p < .05, as well as a significant Shock effect over the last 10 sessions,F( 1,44) = 4.36, p < .05.
RICHARD
.-BLACKOUT
C. COUGHLIN,
JR.
- SHOCK
. ..-.BLACKOUT-NOSHOCK o-NO
BLACKOUT-
O.--ON0
BLACKOUT-NO
”
1
2
”
3
4
SHOCK StiOCK.t’*. 1
” s
‘.
”
6
7
6
”
9
10
”
11
12
’ ”
13
14
15
SESSIONS
of
FIG. 2. Mean Phase 2.
contrast
ratios
for center
key
responding
in S’ during
the
15 sessions
Side Key Responding Timeout responding has been shown to result in a great deal of variability, both between groups and between subjects within the same group (Cough1 in, 1970a). As this is typical of frequency data for which there is a low probability of occurrence (Kirk, 1968), a square-root transformation was used for statistical analysis of the timeout responding in order to normalize these data. Figure 3 shows the mean number of timeouts per session during the Sfor each of the four group~.~ Several aspects of these data are important. First, the two groups which were punished with electric shock for center key responses in S- initially made more timeout responses than the two groups which were not punished. A factorial analysis of variance on the squareroot transformed data for Session 1 revealed that the Shock effect was significant, F( 1,44) = 7.25, p < .05. Pigeons in the two Blackout groups, in which a response on the timeout key produced a blackout of the chamber, also made more responses than those in the corresponding No Blackout groups, in which a response only turned off the response key lights. This difference, however, was not significant. any
’ It should be noted of the birds during
that virtually no responses the S’ component.
were
made
on the
timeout
key
by
TIMEOUT
FIG. 3. Mean
number
of responses
per
FFiOhi
session
301
S-
on the timeout
key
during
Se for the
15 sessions of Phase 2. Second, continued discrimination training resulted in a clear differentiation in timeout responding between the groups, but not in the direction suggested by first session responding. The number of responses for the two Shock groups quickly began to decline, while those in the No Shock groups increased to a higher level of responding. The effect of the blackout contingency remained the same. Within each of the two Shock conditions, Blackout birds took more timeouts from S- than the No Blackout birds. An analysis of variance on these data revealed a significant Shock effect, F( 1,44) = 5.02, p < .05; Blackout effect, F( 1,44) = 4.28, p < .05; and a significant Shock X Session interaction, F( 14,616) = 3.19, p < .OOl. This latter effect reflected the decrease in timeout responding for the Shock groups and the corresponding increase for the No Shozk groups. DISCUSSION
Delivery of response-contingent electric shock for responding to the center key during S-, in addition to extinction, resulted in more response suppression to that key than extinction alone. On the basis of a punishment analysis, it can be concluded that responding to the red key was more aversive for the two Shock groups than for the two No Shock groups (Cough1 in, 1972). It might also be assumed, then, that the con-
302
RICHARD
C.
COUGHLIN,
JR.
ditioned aversive properties of S- were greater for the two Shock groups. It was hypothesized that the greater aversiveness of the punished Swould generate and maintain a higher rate of timeout responding than the S- correlated with extinction alone. This hypothesis was supported only in the first session. Subsequent to the first session, however, average timeout responding increased for the No Shock birds and decreased for the Shock birds, such that, overall, there was less timeout responding by the latter groups. The most reasonable explanation for the inferior performance of the Shock groups on the timeout key is that the aversive properties of the punishment generalized from the S- key. That is, the punishment not only suppressed responding to the center key in S-, but also responding to the side key. Further support for this notion is the difference in the amount of behavioral contrast to the center key during S+. While the average rates of responding to that key did not suppress below the baseline level ( l.OO), the amount of contrast for the Shock groups was clearly suppressed in relation to that of the No Shock groups. A similar finding has been reported by Dinsmoor ( 1952). He showed that when rats were punished with shock for bar-pressing during S-, there was a decrease in S+ response rate. Likewise, Honig and Slivka (1964) showed that punishing responding to one stimulus with electric shock resulted in generalized suppression to the six other randomly presented stimuli. While the situation was different-i.e., all stimuli were being reinforced, and there was no concurrently available response (such as the timeout key)-these data are in general agreement with studies showing that the effects of electric shock usually generalize more extensively than the effects of positive reinforcement (Hearst, 1965). AS in the earlier studies by Coughlin (1970a), the effect of the blackout contingency was significant. When birds could eliminate all illumination from the chamber during S-, there was a greater tendency for them to produce timeouts at a higher rate. One interpretation of this finding is that timeout responding is merely responding for positive reinforcement-in this case, stimulus change reinforcement. Such a notion is consistent with the finding that stimulus change can reinforce responding of rats (McCall, 1965) and of pigeons (Appel, 1963). In the latter study, moreover, the stimulus change interpretation can be made in lieu of an escape-from-high-ratio-FR interpretation. Leitenberg ( 1965) made a similar suggestion, noting that much of the TO-from-positive-reinforcement literature might be handled more parsimoniously by a positive reinforcement maximizing hypothesis. With respect to the data presented here, it could be argued that when a more powerful reinforcer-food-was withdrawn, behavior was maintained by a weaker one-stimulus change.
TIMEOUT
FROM
S-
303
That stimulus change, per se, is responsible for maintaining timeout responding is inconsistent with the finding of Terrace (1971) in which removal of a keylight, other than the S-, did not sustain responses to the timeout key. It could be argued that the amount of stimulus change in that study was not comparable to the blackout of the chamber used in this study. While a direct comparison would be necessary using pigeons, it should be pointed out that a control similar to that of Terrace has been run, using rats as subjects (Goas, 1972). In that study, rats which could produce a blackout without removing the S- responded at a significantly higher rate on a timeout bar than rats which could remove the S- but not produce the blackout. Another interpretation of these findings is that the different degrees of stimulus change merely allowed for more escape; that is, a greater change in aversiveness. Since other stimuli in the chamber could become paired with the S- key, and thus could also acquire aversive properties, the No Blackout groups were able to produce only incomplete escape. Such a notion, however, does not explain the inferior timeout responding of the Shock groups. It seems unlikely that such a mild shock (1 mA) would suppress timeout responses if that response provided an opportunity to escape. There is another possibility. Turning away from the stimulus key is typical behavior for a pigeon during the S- of this kind of successive discrimination (Terrace, 1966), and this behavior was frequently observed in the present experiment, especially during the later sessions. It may be that pigeons learned that turning from the key was a more efficient mode of escape, since such a response did not have to be repeated every 30 sec. If this were the case, then perhaps the reason the Shock birds made fewer timeout responses was that they were making more, or longer, escape responses. These data, then, do not offer any positive conclusions to the hypothesis that S- is a conditioned aversive stimulus. They do suggest the possibility that timeout responding is not a measure of escape from that stimulus, or at least, that it is not an uncontaminated measure. Additional research is necessary either to further evaluate the use of this paradigm as a direct measure of S- aversiveness, or to develop another measure which can directly test that hypothesis, REFERENCES AMSEL, A. Frustrative nonreward in partial reinforcement and discrimination learning: Some recent history and a theoretical extension. Psy&&gical Reuielo, 1962, 69, 306-328. APPEL, J. B. Aversive aspects of a schedule of positive reinforcement. Journal of the Experimental Anu1ysi.s of Behavior, 1963, 6 423428.
RICHARD
304
C. COUGHLIN,
JR.
for delivering shock to pigeons. 10ufd of the %Jeri1959, 2, 161-163. BRETHOWER, 0. M., & REYNOLDS, G. S. A facilitative el%‘ect of punishment on unpunished behavior. Journal of the Experimental Ad@ of Behavior, 196% 5,
AZRIN,
N. H. A technique
mental
Analysis
of Behavior,
192-199.
COIJGHLIN, R. C. Escape from a stimulus correlated with nonreinforcement in a mltiple schedule. Unpublished doctoral dissertation, University of Vermont, 1970. (a) COUGHLIN, R. C. Inexpensive pubis electrodes for delivering shock to pigeons. Joumnl of the Experimental Analysis of Behavior, 1970, 13, 368. (b) COUGHLIN, R. C. The aversive properties of withdrawing positive reinforcement: A review of the recent literature. Psychological Record, 1972, 22, 333-354. hVSMOOR, J. A. A discrimination based on punishment. Quarterly Journal of Erperimental Psychology, 1952, 4, 2745. GOAS, J. A. Timeouts by rats during the auditory S- of a successive discrimination: Escape or stimulus change? Unpublished M. A. Thesis, Fairleigh Dickinson University, 1972. GRUSEC, T. The peak shift in stimulus generalization: Equivalent effects of errors and non-contingent shocks. Journal of the Experimental Analysis of Behuuior, 1968, 11, 239-249. HANSON, H. M. The effects of discrimination training on stimulus generalization. Journal of Experimental Psychology, 1959, 58, 321-334. HEARST, E. Approach, avoidance, and stimulus generalization. In D. Mostofsky (Ed.), Stimulus generalization. Pp. 331-355. Stanford, Calif.: Stanford University Press, 1965. HONIG, W. K., & SLIVK.~, R. M. Stimulus generalization of the effects of punishment. Journal of the Experimental Analysis of Behavior, 1964, 7, 21-25. KIRK, R. E. Experimental design: Procedures for the behavioral sciences. Belmont, Calif.: Brooks-Cole, 1968. LEITENBERG, H. Is time-out from positive reinforcement an aversive event? Psychological Bulletin, 1965, 64, 428441, MCCALL, R. B. Stimulus change in light-contingent bar pressing. Journal of Cornparative and Physiological Psychology, 1965, 59, 439-449. REYNOLDS, G. S. Behavioral contrast. JournaE of the ExpeTimenta~ Analysis of Behavior,
1961,
4, 57-71.
RILLING, M., ASKEW, H. R., AHLSKOG, J. E., & KRAMER, T. J. Aversive properties of the negative stimulus in a successive discrimination. Journal of the Erpe&nental Analysis of Behavior, 1969, 12, 917-932. RrLLrNo, M., KRAhn+ T. J., & RICHARDS, R. W. Aversive properties of the negative stimulus during learning with and without errors. Leaming and Motivation, 1973, 4, l-10. TERRACE, H. S. Stimulus control. In W. K. Honig (Ed.), Operant behavior: Areas of research and application. Pp. 271344. New York: Appleton-Century-Crofts, 1966. TERRACE, H. S. Escape from Se. Learning and Motivation, 1971, 2, 148-163. (Received August 30, 1971)
Timeout
AND
MOTIVATION
from
4, 294-304
( 1973)
a Stimulus
Component
Correlated
of a Multiple
RICHARD Fairleigh
C.
COUGHLIN,
Dickinson
with
the
Extinction
Schedule1 JR.
University
Four groups of pigeons were trained to discriminate between green and red. Pecks on a second key produced a timeout from the schedule in effect for 30 sec. For two of the groups, this timeout response turned off all the lights in the chamber (Blackout), while for the other two, only the keylights were turned off (No Blackout). For one of the Blackout groups and one of the No Blackout groups, responses on the discrimination key during the extinction component (S-) also resulted in a mild electric shock. Blackout groups produced more timeouts during S- than did No Blackout groups, but electric shock punishment suppressed, rather than enhanced, timeout responding. These findings suggest a need for reevaluation of the hypothesis that the timeout response is an escape from an aversive S-.
Researchers in the field of discrimination learning have often made the assumption that the stimulus correlated with the extinction component (S-) of a successive discrimination is an aversive stimulus (Amsel, 1962). Evidence for this notion, however, has been largely indirect. Terrace (1966), for example, suggested that the occurrence of behavioral contrast (Reynolds, 1961) and the peak shift (Hanson, 1959) could be indicative that successive discrimination training has resulted in an aversive S-. Recently, a more direct measure of the aversive properties of S- has been proposed. Using an escape paradigm, Rilling, Askew, Ahlskog, and Kramer (1969) demonstrated that pigeons in a successive discrimination situation would peck a second key in the presence of the S-, if that response produced a SO-set blackout of the chamber. They suggested that S-, in this situation, functioned as a conditioned aversive stimulus from which the birds escaped by making the timeout response. These findings have been substantiated and extended by Rilling, Kramer, and Richards ( 1973) and Terrace ( 1971) . I This research was conducted while the author was supported by a National Dcfense Education Act, Title IV, Predoctoral Fellowship. It is based, in part, on a dissertation submitted to the Graduate College of the University of Vermont in partial fulfillment of the requirements for the Ph.D. degree. Bequests for reprints should be sent to the author, Department of Psychology, Fairleigh Dickinson University, Madison, New Jersey 07940. Copyright All rights
294 @ 1973 by Academic Press, Inc. of reproduction in any form reserved.
TIMEOUT
FROM
S-
295
Coughlin (1970a) also attempted to replicate the findings of Rilling et al. ( 1969), but was unable to find sustained timeout responding during S- when the effects of stimulus change were controlled. In that study, when the timeout response merely removed the key lights, and not the other chamber illumination, timeout responding had ceased for most birds by the tenth session. When the contingency on the timeout key was changed, so that responses produced a total blackout of the chamber, responding reoccurred and was maintained at a high level. It is possible, therefore, that the findings of Rilling and his associates (Rilling et al., 1969, 1973) could be explained in terms of stimulus change reinforcement, rather than in terms of the aversive properties of S-. The findings of Terrace (1971) contradict that conclusion. He used a control for the effects of stimulus change similar to Coughlin (1970a), such that the timeout response only removed the S- keylight. He also ran a control group, for which a response on the timeout key could turn out the timeout keylight, but not the S- keylight or the houselights. Birds in the control group stopped responding quickly, and although the timeout responding of the experimental group declined appreciably during the 15 days of discrimination training, it appeared that the pigeons were still responding. In the Coughlin (1970a) study, however, seven of the 18 birds had ceased responding within 5 days. In light of this apparent contradiction the present study was designed to further examine the role of stimulus change. The contingencies on the timeout key were varied so that for some of the birds, a response on the timeout key produced a blackout, while for the remainder, a response only removed the keylights. This enabled a direct comparison of the effects of the blackout in producing and maintaining the timeout behavior in S-. Whatever the role of stimulus change, it remained to be demonstrated conclusively that the timeout response is an escape response from an aversive stimulus. Crucial to Terrace’s (1966) argument that S- is aversive, are the studies of Brethower and Reynolds (1962) and Grusec (1968). In the former study, it was shown that punishing responses in one component of a multiple schedule resulted in an increase in response rate in the other component. Grusec ( 196S), moreover, showed that noncontingent electric shock in S- either produced or enhanced the peak shift-depending on whether the discrimination had been learned without or with errors, respectively. These studies suggest that the addition of electric shock should be one way of increasing the aversiveness of the S- stimulus. Therefore, this study also looked at the effects of punishing S- responses on timeout behavior. It was hypothesized that punishing re-
296
RICHARD
C.
COUGHLIN,
JR.
sponding in S- with mild electric shock should make the Sthan if it was merely correlated with extinction. If this is the timeout response is really an escape response from an ulus, birds in the shock groups should make more timeout
more aversive the case, and aversive stimresponses.
METHOD
Subjects. The subjects for this experiment were 48 male White Carneaux pigeons, obtained from the Palmetto Pigeon Plant, Sumter, South Carolina. They ranged from 6 mo to 1 yr in age, and were maintained at 80% of their free-feeding body weight for the duration of the experiment. Water was always available in the home cages. Apparatus. Three standard three-key pigeon chambers (Lehigh Valley Electronics, model 1519) were used in this experiment. Either a red or a green light illuminated the center key, while the right-hand key was illuminated with an amber light. Since the left-hand key was not used in this experiment, it was covered with electrical tape. There were two additional sources of illumination in the chamber: a front houselight (2.8 W) located over the center key, and a rear houselight ( 1.12 W) mounted on the opposite wall. Reinforcement was 3-set access to the grain magazine containing a mixture of 50% Kalfir, 40% Vetch, and 10% Hempseed. The experiment was programmed by means of appropriate clocks, counters, and relay circuitry, located in a room adjacent to the experimental room. The shock source was ac line voltage controlled by a variable step-down transformer, connected in series with the subject through a lO,OOO-ohm resistor. Design. Four groups of subjects (?a = 12) were run, using a 2 X 2 factorial design. During the 20 sessions of Phase 1 (prediscrimination training), all birds were treated identically, except for the contingency correlated with the timeout key ( Blackout vs No Blackout). Thus half the birds could produce a blackout by pecking at the amber side key while the other half could only turn off the keylights. On day 21, Phase 2 began and lasted for 15 sessions. In this phase, the groups were further differentiated, this time in terms of the contingencies on the center key during red (S-). For half of the Blackout birds and half of the No Blackout birds the S- key was correlated both with Extinction and with a brief l-mA electric shock for each response on the red key. For the remaining birds, S- was correlated only with Extinction. This design, in terms of the groups and the contingencies on the response keys, is outlined in Table I. Procedure. All pigeons were fitted into a harness (Azrin, 1959) which was connected at one end to l&gauge stainless steel electrodes implanted around the pubis bones (Coughlin, I97Ob). During the experimental sessions this harness was connected to a retractile cable running to the
TIMEOUT
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TABLE Experimental
297
S-
1 Design Response key
Group
Amber Side keya
Green Center key (S+)
Red Center key (S-)
Phase 1 (20 sessions) Response contingency B-S B-NS NB-S NB-NS
Blackout,
VI Wsec
VI 3O-set
No Blackout”
VI 30-set
VI 30-set -
Phase 2 (15 sessions)
-
Response contingency B-S B-NS NB-S NB-NS
Blackout Blackout, No Blackout* No Blackout*
VI VI VI VI
30-set 30-set 30-set 30-set
EXT EXT EXT EXT
a Amber side key illuminated when either red or green is illuminated Response removed schedule in effect for 30 sec. * Key lights turned off-rear houselight remained on. c l-mA shock delivered only if response is made.
19 Shock only & Shock only on center key.
shock source via a freely turning telephone jack located in the ceiling of the chamber. After the pecking response had been conditioned to the green center key, responses on that key were reinforced on a variable-interval 30-set (VI 30-set) schedule. Red and green key lights on the center key were both correlated with reinforcement and were presented alternately. Each stimulus presentation lasted 4 min during which time, the rear houselight was also illuminated. Between each stimulus component, the rear houselight and the keylights were turned off and the front houselight was turned on for 5 sec. The session was terminated after each component had been presented five times. Thus, a session lasted about 40 min. In the first session of VI training, the right-hand side key was illuminated with an amber light. A peck on this key resulted in a 30-set timeout during which time pecks on the keys had no effect. This timeout response either blacked out the entire chamber, or merely turned off the key lights, depending on the group to which a bird had been assigned (see Table 1). At the end of this timeout, the contingencies on the keys were reinstated. The timer controlling the duration of the center-key
298
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component continued to run during the timeout, even though the tapes controlling reinforcement did not. If a timeout occurred when there was less than 30 set remaining for the center-key component, the timeout was terminated by the onset of the 5-set interstimulus interval. Phase 2 began in the session immediately following the 20 daily sessions of Phase 1. During this phase, the red key was correlated with an extinction (EXT) schedule; green continued to be correlated with the VI 30-set schedule. For the birds in the Shock groups (B-S and NB-S) each response to the red key also resulted in a brief (40 msec), 1-mA electric shock. To ensure that the birds in the No Shock groups (B-NS and NB-NS), whose harnesses were also connected to the ceiling jack, would not accidently receive shock, the shock source was disconnected outside the chamber during their sessions. Phase 2 lasted for 15 sessions. Each session ran for about 80 min, and was terminated after each center-key component had been presented 10 times. The birds were run in two replications, with half the birds in each group being run in each replication. RESULTS
Center-Key Responding S-. In order to assesswhether delivering electric shock, contingent on responsesto the S- key, made that stimulus more aversive, a punishment definition of an aversive stimulus was used (Coughlin, 1972). That is, the more suppression that occurs in the presence of a stimulus, the more aversive that stimulus is. Thus, suppression ratios were computed for responding to S-. The baseline was determined by taking the average rate of response to the red key for the last five sessionsof Phase 1 for each bird. This was divided into the response rate of each bird in each session of Phase 2, adjusted for the amount of time actually spent in S-. In other words, since a timeout response reduced the amount of S- time in which further responses to the red key could be made, the rate measure was based only on the time during which the keylights were illuminated. Figure 1 shows the suppression ratios for each of the groups over the 15 sessionsof discrimination training (Phase 2). As can be seen the two Shock groups (B-S & NB-S) suppressed more quickly than the two No Shock groups (B-NS & NB-NS). This difference tended to disappear for the Blackout groups, but for the NO Blackout groups, shock continued to suppress S- responding more than extinction alone. An analysis of variante on these data revealed that the Shock effect was significant, F( 1,44) = 57.92, p < .OOl. There was also a significant Shock x Blackout interaction, F(1,44) = 4.79, p < .05.
TIMEOUT
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FIG. 1. Mean sessions
of Phase
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ratios
for
center
key
responding
in
S- during
the
15
S+. The response rate on the center key during S+ was converted to a ratio similar to that used for the S- data-a contrast ratio, in which a baseline response rate was divided into the daily response rate for Phase 2. Thus, if a bird responded at a rate of 60 responsesper min, as compared to a baseline rate of 40 per min, the ratio for that day would be 1.50. This allowed for direct comparison of the changes in S+ rate for all groups. Through the fourth session, the groups all showed about the same amount of contrast, as can be seen in Fig. 2. After that session,the curves for the Shock groups separated from those of the No Shock groups. In other words, the No Shock groups showed more behavioral contrast than the Shock groups. An analysis of variance on the contrast ratios revealed that the Shock effect failed to reach significance, F( 1,44) = 3.78, p > .05. There was, however, a significant Shock x Session interaction, F( 14,616) = 2.30, p < .05, as well as a significant Shock effect over the last 10 sessions,F( 1,44) = 4.36, p < .05.
RICHARD
.-BLACKOUT
C. COUGHLIN,
JR.
- SHOCK
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2
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‘.
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6
7
6
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9
10
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11
12
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14
15
SESSIONS
of
FIG. 2. Mean Phase 2.
contrast
ratios
for center
key
responding
in S’ during
the
15 sessions
Side Key Responding Timeout responding has been shown to result in a great deal of variability, both between groups and between subjects within the same group (Cough1 in, 1970a). As this is typical of frequency data for which there is a low probability of occurrence (Kirk, 1968), a square-root transformation was used for statistical analysis of the timeout responding in order to normalize these data. Figure 3 shows the mean number of timeouts per session during the Sfor each of the four group~.~ Several aspects of these data are important. First, the two groups which were punished with electric shock for center key responses in S- initially made more timeout responses than the two groups which were not punished. A factorial analysis of variance on the squareroot transformed data for Session 1 revealed that the Shock effect was significant, F( 1,44) = 7.25, p < .05. Pigeons in the two Blackout groups, in which a response on the timeout key produced a blackout of the chamber, also made more responses than those in the corresponding No Blackout groups, in which a response only turned off the response key lights. This difference, however, was not significant. any
’ It should be noted of the birds during
that virtually no responses the S’ component.
were
made
on the
timeout
key
by
TIMEOUT
FIG. 3. Mean
number
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per
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301
S-
on the timeout
key
during
Se for the
15 sessions of Phase 2. Second, continued discrimination training resulted in a clear differentiation in timeout responding between the groups, but not in the direction suggested by first session responding. The number of responses for the two Shock groups quickly began to decline, while those in the No Shock groups increased to a higher level of responding. The effect of the blackout contingency remained the same. Within each of the two Shock conditions, Blackout birds took more timeouts from S- than the No Blackout birds. An analysis of variance on these data revealed a significant Shock effect, F( 1,44) = 5.02, p < .05; Blackout effect, F( 1,44) = 4.28, p < .05; and a significant Shock X Session interaction, F( 14,616) = 3.19, p < .OOl. This latter effect reflected the decrease in timeout responding for the Shock groups and the corresponding increase for the No Shozk groups. DISCUSSION
Delivery of response-contingent electric shock for responding to the center key during S-, in addition to extinction, resulted in more response suppression to that key than extinction alone. On the basis of a punishment analysis, it can be concluded that responding to the red key was more aversive for the two Shock groups than for the two No Shock groups (Cough1 in, 1972). It might also be assumed, then, that the con-
302
RICHARD
C.
COUGHLIN,
JR.
ditioned aversive properties of S- were greater for the two Shock groups. It was hypothesized that the greater aversiveness of the punished Swould generate and maintain a higher rate of timeout responding than the S- correlated with extinction alone. This hypothesis was supported only in the first session. Subsequent to the first session, however, average timeout responding increased for the No Shock birds and decreased for the Shock birds, such that, overall, there was less timeout responding by the latter groups. The most reasonable explanation for the inferior performance of the Shock groups on the timeout key is that the aversive properties of the punishment generalized from the S- key. That is, the punishment not only suppressed responding to the center key in S-, but also responding to the side key. Further support for this notion is the difference in the amount of behavioral contrast to the center key during S+. While the average rates of responding to that key did not suppress below the baseline level ( l.OO), the amount of contrast for the Shock groups was clearly suppressed in relation to that of the No Shock groups. A similar finding has been reported by Dinsmoor ( 1952). He showed that when rats were punished with shock for bar-pressing during S-, there was a decrease in S+ response rate. Likewise, Honig and Slivka (1964) showed that punishing responding to one stimulus with electric shock resulted in generalized suppression to the six other randomly presented stimuli. While the situation was different-i.e., all stimuli were being reinforced, and there was no concurrently available response (such as the timeout key)-these data are in general agreement with studies showing that the effects of electric shock usually generalize more extensively than the effects of positive reinforcement (Hearst, 1965). AS in the earlier studies by Coughlin (1970a), the effect of the blackout contingency was significant. When birds could eliminate all illumination from the chamber during S-, there was a greater tendency for them to produce timeouts at a higher rate. One interpretation of this finding is that timeout responding is merely responding for positive reinforcement-in this case, stimulus change reinforcement. Such a notion is consistent with the finding that stimulus change can reinforce responding of rats (McCall, 1965) and of pigeons (Appel, 1963). In the latter study, moreover, the stimulus change interpretation can be made in lieu of an escape-from-high-ratio-FR interpretation. Leitenberg ( 1965) made a similar suggestion, noting that much of the TO-from-positive-reinforcement literature might be handled more parsimoniously by a positive reinforcement maximizing hypothesis. With respect to the data presented here, it could be argued that when a more powerful reinforcer-food-was withdrawn, behavior was maintained by a weaker one-stimulus change.
TIMEOUT
FROM
S-
303
That stimulus change, per se, is responsible for maintaining timeout responding is inconsistent with the finding of Terrace (1971) in which removal of a keylight, other than the S-, did not sustain responses to the timeout key. It could be argued that the amount of stimulus change in that study was not comparable to the blackout of the chamber used in this study. While a direct comparison would be necessary using pigeons, it should be pointed out that a control similar to that of Terrace has been run, using rats as subjects (Goas, 1972). In that study, rats which could produce a blackout without removing the S- responded at a significantly higher rate on a timeout bar than rats which could remove the S- but not produce the blackout. Another interpretation of these findings is that the different degrees of stimulus change merely allowed for more escape; that is, a greater change in aversiveness. Since other stimuli in the chamber could become paired with the S- key, and thus could also acquire aversive properties, the No Blackout groups were able to produce only incomplete escape. Such a notion, however, does not explain the inferior timeout responding of the Shock groups. It seems unlikely that such a mild shock (1 mA) would suppress timeout responses if that response provided an opportunity to escape. There is another possibility. Turning away from the stimulus key is typical behavior for a pigeon during the S- of this kind of successive discrimination (Terrace, 1966), and this behavior was frequently observed in the present experiment, especially during the later sessions. It may be that pigeons learned that turning from the key was a more efficient mode of escape, since such a response did not have to be repeated every 30 sec. If this were the case, then perhaps the reason the Shock birds made fewer timeout responses was that they were making more, or longer, escape responses. These data, then, do not offer any positive conclusions to the hypothesis that S- is a conditioned aversive stimulus. They do suggest the possibility that timeout responding is not a measure of escape from that stimulus, or at least, that it is not an uncontaminated measure. Additional research is necessary either to further evaluate the use of this paradigm as a direct measure of S- aversiveness, or to develop another measure which can directly test that hypothesis, REFERENCES AMSEL, A. Frustrative nonreward in partial reinforcement and discrimination learning: Some recent history and a theoretical extension. Psy&&gical Reuielo, 1962, 69, 306-328. APPEL, J. B. Aversive aspects of a schedule of positive reinforcement. Journal of the Experimental Anu1ysi.s of Behavior, 1963, 6 423428.
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JR.
for delivering shock to pigeons. 10ufd of the %Jeri1959, 2, 161-163. BRETHOWER, 0. M., & REYNOLDS, G. S. A facilitative el%‘ect of punishment on unpunished behavior. Journal of the Experimental Ad@ of Behavior, 196% 5,
AZRIN,
N. H. A technique
mental
Analysis
of Behavior,
192-199.
COIJGHLIN, R. C. Escape from a stimulus correlated with nonreinforcement in a mltiple schedule. Unpublished doctoral dissertation, University of Vermont, 1970. (a) COUGHLIN, R. C. Inexpensive pubis electrodes for delivering shock to pigeons. Joumnl of the Experimental Analysis of Behavior, 1970, 13, 368. (b) COUGHLIN, R. C. The aversive properties of withdrawing positive reinforcement: A review of the recent literature. Psychological Record, 1972, 22, 333-354. hVSMOOR, J. A. A discrimination based on punishment. Quarterly Journal of Erperimental Psychology, 1952, 4, 2745. GOAS, J. A. Timeouts by rats during the auditory S- of a successive discrimination: Escape or stimulus change? Unpublished M. A. Thesis, Fairleigh Dickinson University, 1972. GRUSEC, T. The peak shift in stimulus generalization: Equivalent effects of errors and non-contingent shocks. Journal of the Experimental Analysis of Behuuior, 1968, 11, 239-249. HANSON, H. M. The effects of discrimination training on stimulus generalization. Journal of Experimental Psychology, 1959, 58, 321-334. HEARST, E. Approach, avoidance, and stimulus generalization. In D. Mostofsky (Ed.), Stimulus generalization. Pp. 331-355. Stanford, Calif.: Stanford University Press, 1965. HONIG, W. K., & SLIVK.~, R. M. Stimulus generalization of the effects of punishment. Journal of the Experimental Analysis of Behavior, 1964, 7, 21-25. KIRK, R. E. Experimental design: Procedures for the behavioral sciences. Belmont, Calif.: Brooks-Cole, 1968. LEITENBERG, H. Is time-out from positive reinforcement an aversive event? Psychological Bulletin, 1965, 64, 428441, MCCALL, R. B. Stimulus change in light-contingent bar pressing. Journal of Cornparative and Physiological Psychology, 1965, 59, 439-449. REYNOLDS, G. S. Behavioral contrast. JournaE of the ExpeTimenta~ Analysis of Behavior,
1961,
4, 57-71.
RILLING, M., ASKEW, H. R., AHLSKOG, J. E., & KRAMER, T. J. Aversive properties of the negative stimulus in a successive discrimination. Journal of the Erpe&nental Analysis of Behavior, 1969, 12, 917-932. RrLLrNo, M., KRAhn+ T. J., & RICHARDS, R. W. Aversive properties of the negative stimulus during learning with and without errors. Leaming and Motivation, 1973, 4, l-10. TERRACE, H. S. Stimulus control. In W. K. Honig (Ed.), Operant behavior: Areas of research and application. Pp. 271344. New York: Appleton-Century-Crofts, 1966. TERRACE, H. S. Escape from Se. Learning and Motivation, 1971, 2, 148-163. (Received August 30, 1971)