Retardation of autoshaping following pretraining with unpredictable food: Effects of changing the context between pretraining and testing

LEARNING

AND

MOTIVATION

11,

117-134 (1980)

Retardation of Autoshaping following Pretraining with Unpredictable Food: Effects of Changing the Context between Pretraining and Testing ARTHUR TOMIE,ARTHUR

L. MURPHY,ANDSTEPHENFATH

Rutgers-The

State University AND

RAYMOND L. JACKSON University

of

Colorado

In Experiment 1, pigeons exposed to US ONLY pretraining were observed to be retarded in the acquisition of autoshaping relative to naive controls; however, gross changes in contextual stimuli between pretraining and testing alleviated the retardation effect. In Experiment 2, groups of pigeons exposed to CS ONLY, US ONLY, or random CS-US presentations (TRC) were tested for the acquisition of autoshaping. The US ONLY and TRC groups were retarded relative to naive controls. The context change manipulation eliminated the US ONLY retardation effect and attenuated, but did not eliminate, the TRC retardation effect. Context blocking accounts for the US ONLY effect and contributes to the TRC effect; however, context-independent retardation following TRC pretraining suggests the operation of the learned irrelevance cognition.

Brown and Jenkins (1968) reported that hungry pigeons would begin pecking a lighted response key (CSl) if illumination of the key signaled the forthcoming presentation of grain (US). Despite the reliability of the autoshaping phenomenon, a number of pretraining manipulations have been shown to proactively interfere with the acquisition of the keypecking response. These include uncorrelated CS2 and food presentations This research was supported by National Institute of Mental Health Postdoctoral Fellowship MH 05182-01, National Institute of Mental Health Grant MH 29425-01, National Science Foundation Grant BNS 77-20564, Biomedical Sciences Support Grant administered by Rutgers University, and Rutgers Research Council Grants awarded to the senior author. The authors thank C. F. Hickis and D. Abbondandolo for assistance in the running of subjects. Requests for reprints should be sent to Arthur Tonne, Department of Psychology, Busch Campus, Rutgers University, New Brunswick, NJ 08903. 117 0023-9690/80/010117-18$02.00/O Copyright @ 1980 by Academic Press, Inc. All rights of reproduction in any form reserved.

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(where CS2 differs from CSI) (Hall & Honig, 1974; Tomie, 1976a, 1976b), uncorrelated CSl and food presentations (Gamzu & Williams, 1971, 1973; Mackintosh, 1973; Wasserman, Franklin, & Hearst, 1974), and unsignaled food presentations (Engberg, Hansen, Welker, & Thomas, 1972; Tomie, 1976b; Wasserman, 1972). Investigators have commonly appealed to cognitive factors such as general inattentiveness (Hall & Honig, 1974), learned irrelevance (Mackintosh, 1973), and learned laziness (Engberg et al., 1972) in order to account for the deleterious effects of such pretraining upon autoshaping. Although the particulars of the accounts differ, they share the premise that the retarded acquisition of autoshaping is a general transfer-oftraining effect. That is, during pretraining the subject learns that the US is unpredictable. This learning engenders associative impairment which proactively interferes with the acquisition of autoshaping. Recently, Tomie (1976a, 1976b) has suggested an alternative formulation which may provide a unified, integrated account of these various retardation effects. Tomie has argued that pretraining with unpredictable US presentations may condition the context; furthermore, the excitatory context may function as a blocking stimulus (cf. Kamin, 1969) during the subsequent acquisition of autoshaping. Empirical support for the context-blocking hypothesis is derived from the observation that the speed of acquisition of autoshaping is inversely related to the degree to which background contextual stimuli have been paired with the US (Blanchard & Honig, 1976). That is, autoshaping is retarded when it is administered in the presence of a static former CS+ for food, relative to when it is administered in the presence of either a former CS- or a novel CS. This result is consistent with the assumption of the context-blocking hypothesis that autoshaping may be blocked by embedding the CS used in autoshaping within a nonlocalized background CS that has been extensively paired with the US. Further support for the context-blocking hypothesis has been provided by Tomie (1976a, 1976b) who found that the retardation of autoshaping following pretraining with uncorrelated CS2 and food presentations is a context-specific phenomenon. That is, subjects administered pretraining wherein CS2 (tone or red keylight) was presented randomly with respect to the food US were subsequently retarded in autoshaping to a green keylight CS, relative to control subjects with no pretraining experience. However, these differences were eliminated when pretraining and testing were administered in the presence of different contextual stimuli. The context-blocking hypothesis specifies that the retardation depends upon the presence of those contextual stimuli that were present during initial training. If pairing of the context with food leads to the development of an excitatory context, then the presentation of the context in the absence of

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food ought to extinguish its excitatory properties. Since a context without excitatory properties should be ineffective as a blocking stimulus, one would expect that the retardation of autoshaping following pretraining with unpredictable food would be alleviated by interpolating nonreinforced context exposure between pretraining and testing. Tomie (1976b, Experiment 2) has reported that the deleterious effects of US-only pretraining upon the subsequent acquisition of autoshaping are alleviated by such a context extinction manipulation. It appears, therefore, that the retarding influence of uncorrelated CS2food pretraining (i.e., general inattentiveness treatment) is alleviated by the context change manipulation and the retarding influence of US-only pretraining (i.e., learned laziness treatment) is alleviated by the context extinction manipulation. Note that the context change manipulation has been limited in its application to the case wherein pretraining with unpredictable food is administered in conjunction with a randomly presented CS2 which differs from the test CS used in autoshaping. The present experiments focus upon the effects of changing the background contextual stimuli between pretraining and testing for autoshaping when the pretraining manipulation involves unsignaled US presentations (Experiment 1) and randomly related presentations of the green keylight autoshaping CS-to-be and food (Experiment 2). EXPERIMENT

1

The present experiment was designed to assess the generality of the observation that the retardation of autoshaping following pretraining with unpredictable US presentations is a context-specific phenomenon. Pigeons were tested for the acquisition of autoshaped keypecking to a green keylight CS following extended exposure to intermittent, unsignaled food (US). Half of these subjects were pretrained in the context subsequently used during the test for autoshaping, whereas half were pretrained in a different context. The contexts differed in the presence or absence of cardboard lining of the experimental chamber. Retardation effects were evaluated against an original learning control group (OLC) of experimentally naive animals. Method Subjects. The subjects were 32 experimentally naive adult pigeons obtained from a local supplier and maintained at 70-75% of their ad fib. weights throughout the experiment. Subjects were housed in individual cages and given free access to grit and water. Apparatus. Four standard pigeon chambers were used, with associated automatic programming and recording equipment. Each chamber measured 35 x 35 x 30 cm (L x W x H), with a metal intelligence panel on the front containing a 2.9-cm diameter pecking key centered 20 cm above

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a wire grid floor. Stimuli could be projected onto the response key by Industrial Electronics Engineers in-line display cells equipped with GE 1815 miniature lamps and Kodak Wratten Filter No. 99 which provided chromatic light with peak wavelength transmission at 555 nm. The foodhopper aperture was located directly below the pecking key. A houselight was mounted behind a 2.4-cm-wide strip of white Plexiglas located above the intelligence panel and provided ambient illumination of the conditioning chamber. A white noise generator provided 92 db (SPL) of masking noise delivered through a 3-in. (7.62-cm) cone speaker mounted to the right of the food-hopper aperture. Masking noise was used in conjunction with the unlined chambers only (see below). Procedure. Prior to the initiation of the experiment, the 32 subjects were unsystematically divided into four groups of eight subjects each. On Day 1, the 16 subjects in the US ONLY condition were trained to approach and eat from the food hopper. During hopper training the response key was unilluminated. Hopper presentations were made according to a variable-time (VT) 30-set schedule. Thirty hopper presentations were given on Day 1, and subjects were allowed to feed for 4 set per hopper presentation. Half of the subjects (identified as in the IZO change condition) were hopper-trained in the chamber in its normal condition. The other half (identified as in the change condition) were hopper-trained in a brown corrugated cardboard liner which was built to fit the full inside dimensions of the conditioning chamber. The only apertures in the liner were cut to accomodate the food-hopper, response key, and speaker grill. All subjects then received their pretraining in the context in which they were hopper-trained. On Day 2, the 16 subjects in the US ONLY condition received the first of 30 daily sessions of training, consisting of 30 presentations of 4-set access to a tray of mixed pigeon grain (US). Following 30 days of training, the US ONLY subjects were tested for the acquisition of autoshaping in the unlined chamber. Thus, for the eight subjects in the change condition, training was conducted in a cardboard environment, with cardboard floors, no ambient illumination, and no masking noise, whereas testing for autoshaping was conducted in a white plastic environment with a gray metal intelligence panel, wire-grid floor, ambient illumination, and masking noise. Autoshaping trials consisted of the illumination of the response key by a light of 555 nm for the 6 set immediately preceding responseindependent 4-set access to grain. Autoshaping trials were programmed according to the VT 30-set schedule used in pretraining. Thirty autoshaping trials were administered per session. Subjects were run for 10 sessions. The 16 remaining subjects were hopper-trained on the day immediately preceding the test for the acquisition of autoshaping and served as original learning controls (OLC). Half of the subjects were hopper-trained in the

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autoshaping context (no change), while half were hopper-trained cardboard context (change).

121 in the

Results and Discussion The mean acquisition functions for autoshaped pecking in each of the four groups of subjects are presented in Fig. 1. As the figure reveals, the subjects in the US ONLY-no change group were retarded in the acquisition of autoshaping relative to subjects in the remaining three groups. The data were entered into a three-way, mixed-design, analysis of variance, with treatment (US ONLY vs OLC), context (change vs IZOchange), and blocks of trials as factors. In this and all subsequent analyses the (Ylevel was set at .05. The analysis revealed a reliable main effect of treatment [F(l, 28) = 22.501, a reliable main effect of context [F(l, 28) = 11.471, a reliable two-way interaction between treatment and context [F( 1, 28) = 11.431, and a reliable three-way interaction between treatment, context, and trials [F(29, 812) = 1.731. To isolate the source of the three-way interaction, two separate two-way treatment by trials analyses of variance were performed on the two levels of the context variable. The analyses indicated that under the IZO change condition, there was a reliable main effect of treatment [F( 1, 14) = 21.493 and a reliable treatment by trials interaction [F(49,406) = 3.653; however, in the change condition neither of these effects approached significance. This pattern of results indicates that the effects of the type of pretraining upon the acquisition of autoshaping depended upon the presence of absence of a context change. Additional evidence that the groups differed in the speed of acquisition of autoshaping was provided by a measure of the number of trials required by each of the subjects to acquire a criterion of responding on five

li BLOCKS

OF TEN

20

TRIALS

FIG. 1. Mean number of trials with one or more responses as a function of 10 trial blocks for US ONLY-no change, US ONLY-change, OLC-no change. and OLC-change groups.

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consecutive trials. The mean number of trials to criterion was 214.88, 81.38, 51.13, and 49.13 for groups US ONLY-no change, US ONLYchange, OLC-no change, and OLC-change, respectively. The data were entered into a two-way analysis of variance which revealed a reliable interaction between treatment and context, [F( 1, 28) = 11.1 I]. Furthermore, a Duncan multiple range test revealed that the US ONLY-no change group differed reliably from each of the other groups, which did not differ from each other. The performance of the US ONLY-no change group replicates the observation that extended pretraining with intermittent, unsignaled food retards the acquisition of subsequent autoshaping (Engberg et al., 1972). However, this retardation effect appears to be context specific, since gross changes in the background contextual stimuli prior to the initiation of the acquisition test almost completely alleviate the deleterious effects of such pretraining. The overall pattern of results obtained in this experiment follows directly from the context-blocking hypothesis and strains nonspecific transfer interpretations (e.g., “learned laziness”) of the retardation effect. EXPERIMENT

2

The purpose of this experiment was to determine the degree to which the “learned irrelevance” effect (cf. Mackintosh, 1973) is influenced by manipulation of the context. Following various types of pretraining groups of pigeons were tested for the acquisition of autoshaping to a greer keylight CS. The groups were arranged in a 4 by 2 factorial design with four levels of type of pretraining (green keylight CS ONLY, US ONLY, green keylight Truly Random Control, and Original Learning Control) and two levels of context treatment (Context Change, No Context Change). The green keylight CS ONLY (latent inhibition), US ONLY (learned laziness), and green keylight TRC (learned irrelevance) procedures would be expected to retard the acquisition of autoshaping relative to the OLC. The design allows for the comparison of the retarding effectiveness of each of these procedures as well as an assessment of their contextual specificity. Direct comparison of treatment effects in and out of context would allow for the evaluation of the contribution of latent inhibition and learned laziness to the learned irrelevance retardation effect. Method Subjects. The subjects were 96 experimentally naive adult pigeons obtained from a local supplier and maintained at 70-75% of their ad lib weights throughout the experiment. Subjects were housed in individual metal cages and given free access to grit and water. Apparatus. Four standard pigeon chambers similar to those described in Experiment 1 were used. Context liners were constructed out of 0.25

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in. masonite. Eighty-two decibels of masking noise was provided by the exhaust fans (rather than by a white noise generator), which were continuously operative during all phases of the experiment. Procedure. Prior to the initiation of the experiment, the 96 subjects were unsystematically divided into eight groups of 12 subjects each. On Day 1, the 48 subjects in the US ONLY and green keylight Truly Random Control (TRC) conditions were trained to approach and eat from the food hopper. During hopper training the response key was unilluminated. Hopper presentations were made according to a variable-time (VT) 45set schedule. Sixty hopper presentations were given on Day 1, and subjects were allowed to feed for 5-set per hopper presentation. Half of the subjects (identified as in the 110change condition) were hopper-trained in the chamber in its normal condition. The other half (identified as in the change condition) were hopper-trained in a brown masonite liner which was built to fit the full inside dimensions of the conditioning chamber. All subjects then received their pretraining in the context in which they were hopper-trained. On Day 2, these 48 subjects received the first of 30 daily sessions of training. The 24 subjects in the US ONLY condition received daily sessions consisting of 60 presentations of 5-set access to a tray of mixed pigeon grain (US). The US presentations were programmed according to a VT 45set schedule. The 24 subjects in the green keylight TRC condition received similar training; however, in addition to the US presentations, each daily session provided for a comparable number of illuminations of the pecking key by a light of 555 nm for 7.5 set (CS). The CS and US presentations were arranged to occur randomly with respect to one another by the use of independent 16-mm film readers. Following 30 days of training, the 48 subjects were tested for the acquisition of autoshaping in the unlined chamber. Autoshaping trials consisted of the illumination of the response key by a light of 555 nm for the 7.5 set immediately preceding response-independent 5-set access to grain. Autoshaping trials were programmed according to the VT 45-set schedule used in pretraining. Sixty autoshaping trials were administered per session. Subjects were run for eight sessions. The 24 subjects in the green keylight CS ONLY condition received 30 daily sessions of training consisting of 60 CS presentations (555-nm illumination of response key for 7.5 set) programmed according to a VT 45-set schedule. Half of the subjects were administered their pretraining in the masonite liners, while the other half were administered their pretraining in the unlined chambers. On Day 31 all subjects were hopper-trained (as described above) in their pretraining environment, and on Day 32 all subjects received the first of eight daily sessions of testing for the acquisition of autoshaping in the unlined chambers (as described above). The 24 subjects in the Original Learning Control (OLC) condition were

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hopper-trained immediately preceding the test for the acquisition of autoshaping. Autoshaping trials were initiated when the subject attained a hopper-training criterion of feeding on five consecutive presentations of the hopper. Half of the subjects were hopper-trained in the unlined autoshaping context (no change), while half were hopper-trained in the masonite context (change). Results and Discussion

The mean autoshape acquisition functions for the green keylight CS ONLY, US ONLY, and green keylight TRC groups are shown relative to the OLC groups in Figs. 2, 3, and 4, respectively. The data were entered into a three-way, mixed design 4 x 2 x 48 analysis of variance with treatment (OLC, green keylight CS ONLY, US ONLY, and green keylight TRC), context (change, no change) and blocks of 10 trials as factors. The overall analysis revealed a reliable main effect of treatment [F(3, 88) = 4.421, a reliable main effect of context [F(l, 88) = 9.591, and a marginally reliable treatment by context interaction [F(3, 88) = 2.40, p < .lO]. In order to evaluate specific treatment and context effects each of the pretraining procedures is compared with the OLC. As can be seen in Fig. 2, all of the groups in the green keylight CS ONLY and OLC conditions acquired the autoshaping response rapidly. The data were entered into a three-way mixed design analysis of variance, with treatment (green keylight CS ONLY vs OLC), context (change vs no change), and blocks of trials as factors. The analysis revealed a reliable main effect of treatment [F( 1, 44) = 5.111, indicating that the green keylight CS ONLY groups acquired the autoshaping response more rapidly than did the OLC

10 20 30 40 50 BLOCKS OF TEN TRIALS FIG. 2. Mean number of trials with one or more responses as a function of 10 trial blocks for green keylight CS ONLY-no change, green keylight CS ONLY-change, OLC-no change, and OLC-change groups.

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AND AUTOSHAPING

CONTEXT NO CONTEXT

OLC o .

CtlA16E CHANGE

10 20 30 40 BLOCKS OF TEN TRIALS

US-ONLY 0 .

50

FIG. 3. Mean number of trials with one or more responses as a function of’ 10 trkJ bb&s for US ONLY-no change, US ONLY-change, OLC-no change, and OLC-chnge groups.

groups. The analysis indicated no main effect of context (F < 1) and no interaction effects among treatment and context. Inspection of Fig. 3 reveals that the US ONLY-no change group was retarded in the acquisition of autoshaping and exhibited a suppressed asymptotic level of probability of responding, relative to the other three groups. The data were entered into a three-way mixed design analysis of variance which revealed no main effects of treatment or context, but a reliable treatment by context interaction [F(l, 44) = 5.071 and a reliable three-way interaction between treatment, context, and blocks of trials EF(47, 2068) = 1.861. To isolate the source of the three-way interaction,

CONTEXT NO CONTEXT

CHAMX CtlANLWOE

OLC 0 l

10 20 30 40 BLOCKS OF TEN TRIALS

O-TRC 0 l

50

FIG. 4. Mean number of trials with one or more responses as a function of 10 trial blocks for green keylight TRC-no change, green keylight TRC-change, OLC-no change,and OLC-chzge groups.

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two separate two-way treatment by blocks analyses of variance were performed on the two levels of the context variable. The analyses indicated that under the no change condition, there was a reliable main effect of treatment, [F( 1, 22) = 2.611, indicating that the acquisition function of the US ONLY-no change group is reliably retarded relative to the OLC-no change group; however, under the change condition the effect of treatment failed to approach significance, F < 1. The effectiveness of the context change in alleviating the retardation effect can be evaluated by directly comparing the acquisition function of the US ONLY-no change group with the acquisition function of the US ONLY-change group. A two-way mixed design context by blocks analysis of variance revealed a reliable main effect of context [F(l, 22) = 6.641 and a reliable context by blocks interaction [F(47, 1034) = I.621 indicating that the implementation of a context change reliably attenuates the deleterious effects of US ONLY pretraining upon subsequent autoshaping. It is appropriate to note that the pattern of results presented in Fig. 3 replicates the results of Experiment 1 despite procedural differences in CS and US duration, pretraining and testing schedule, and manipulation of the auditory context. Inspection of Fig. 4 reveals that the green keylight TRC-no change group was retarded in the acquisition of autoshaping and exhibited a suppressed asymptotic level of probability of responding, relative to the other three groups. The data were entered into a three-way mixed design analysis of variance which revealed no main effects of treatment or context, but a marginally reliable treatment by context interaction [F(l, 44) = 3.72, p < . lo]. To isolate the source of the interaction, two separate two-way treatment by blocks analyses of variance were performed on the two levels of the context variable. The analyses indicated that under the no change condition, there was a reliable main effect of treatment [F(l, 22) = 7.85, p < .05] indicating that the acquisition function of the green keylight TRC-no change group is reliably retarded relative to the OLC-no change group; however, under the change condition the effect of treatment failed to approach significance, F < 1. A direct comparison of the acquisition functions of the two green keylight TRC groups reveals a reliable main effect of context [F( 1, 22) = 4.541, indicating that the implementation of a context change reliably alleviates the retarding influence of “learned irrelevance” pretraining. The similarity of the effects of the US ONLY and green keylight TRC treatments is revealed by a three-way mixed design analysis of variance with treatment (US ONLY vs green keylight TRC), context (change vs no change) and blocks of 10 trials as factors. The analysis revealed a reliable main effect of context [F( 1,44) = 11.091 but no effects of treatment which approached significance.

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The green keylight CS ONLY and green keylight TRC treatments differ in that the latter provides for unpredictable US presentations. Since the former facilitates and the latter retards acquisition relative to the OLC, it may be inappropriate to evaluate the retarding properties of the green keylight TRC treatment relative to the OLC baseline. That is, the retarding effect of unpredictable US presentations within the green keylight TRC treatment may be opposed by the antagonistic influence of the facilitative green keylight CS ONLY effect. The effects of the unpredictable food administered via the green keylight TRC procedure may be evaluated by comparing the effects of the green keylight CS ONLY and green keylight TRC treatments. Accordingly, a 2 x 48 mixed design analysis of variance was performed on each level of the context variable with treatment (green keylight CS ONLY vs green keylight TRC) and blocks of 10 trials as factors. The analysis revealed reliable treatment effects under both the change and no change conditions [F( 1,22) = 5.88, and F( 1,22) = 10.74, respectively]. Therefore, it appears that unpredictable food administered during the green keylight TRC procedure retards the acquisition of autoshaping relative to the green keylight CS ONLY groups; furthermore, the retardation effect transcends the introduction of a context change. Additional evidence that the groups differed in the speed of acquisition of autoshaping was provided by a measure of the number of trials required by each of the subjects to attain a criterion of responding on five consecutive trials. The mean number of trials to criterion was 186.3, 182.4, 134.3, 78.3,75.8,72.3,66.2, and 44.3 for groups green keylight TRC-no change, US ONLY-no change, green keylight TRC-change, US ONLY-change, OLC-no change, OLC-change, green keylight CS ONLY-no change, and green keylight CS ONLY-change, respectively. The data were entered into a two-way analysis of variance which revealed a reliable main effect of treatment [F(3, 88) = 5.093 and a reliable main effect of context [F( 1,88) = 4.401. A Duncan multiple range test (a = .05) revealed that the green keylight TRC-no change group and the US ONLY-no change group were reliably retarded relative to the five fastest groups. All other comparisons were nonsignificant. GENERAL DISCUSSION Experiment 1 replicates the “learned laziness” effect (cf. Engberg et al., 1972) and demonstrates that the retardation of autoshaping following US ONLY pretraining is a context-specific effect. Experiment 2 replicates the results of Experiment 1, and, furthermore, provides evidence that the “learned irrelevance” effect (cf. Mackintosh, 1973) is in part dependent upon the administration of pretraining and testing in the same environment. This pattern of results suggests that retardation effects in autoshap-

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ing following pretraining with unpredictable food which have been attributed to cognitive transfer-of-training deficits may be attributed to the blocking inlluence of the static, contextual stimuli. Although the pattern of results observed in Experiment 2 under the no change condition replicates the “learned irrelevance” effect, several aspects of the data are at variance with those reported by Mackintosh (1973). In both experiments, asymptotic performance levels of key pecking were suppressed; however, Mackintosh observed minimal retardation of keypeck acquisition following US ONLY pretraining, whereas in the present experiment the retardation effect following such pretraining was comparable to that observed following green keylight TRC pretraining. There are a number of differences in procedures which could conceivably account for the discrepancy. The major procedural difference involves the number of unpredictable feedings administered during pretraining. Mackintosh administered 160 US ONLY presentations (four sessions of 40 feedings per session), whereas there were 900 such unpredictable feedings in the present experiment. A positive relationship between the number of US presentations and the magnitude of subsequently observed retardation of acquisition has been documented by a number of autoshaping investigators (cf. Downing & Neuringer, 1976; Schwartz & Balsam, 1979); therefore, the failure to observe robust retardation following abbreviated US ONLY pretraining is not surprising. That Mackintosh did observe substantial retardation following random presentations of the CS and US (160 presentations of each) suggests that “learned irrelevance” and “learned laziness” are not isomorphic effects (as suggested by the context blocking analysis). There is, in fact, some evidence from Experiment 2 which suggests that the “learned irrelevance” effect is not entirely attributable to context blocking. The green keylight TRC-change group was still somewhat retarded in the acquisition of autoshaping relative to the US ONLY-change and OLC-change groups (see trials to criterion data). The failure to completely alleviate the “learned irrelevance” retardation effect is particularly surprising in view of the fact that the green keylight CS is occasionally paired with the US during pretraining and such pairings might be expected to establish the CS as a signal for food (cf. Ayres, Benedict, & Witcher, 1975; Benedict & Ayres, 1972; Kremer, 1971, 1974), which should facilitate the development of autoshaping. In summary, the persistence of retardation following a context change suggests that there is more to the “learned irrelevance” effect than merely blocking by the context. This additional retardation engendered by green keylight TRC pretraining is not necessarily exhibited in all green keylight TRC vs US ONLY comparisons, since the green keylight TRC procedure may generate excitatory conditioning to the green keylight CS and

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this effect may mask the “learned irrelevance” factor by countering its influence. Preexposure to the green keylight CS may reduce the magnitude of the learned irrelevance effect in still another way. Note that CS preexposure facilitated rather than retarded the acquisition process (see Fig. 2). The retarding influence of unpredictable food administered within the learned irrelevance treatment may be greater than the effect of the US ONLY manipulation per se. That is, the antagonistic facilitative effect of extended CS preexposure may subtract from the retarding effect of USs administered during the learned irrelevance treatment. Such a point of view would encourage the direct comparison of green keylight TRC with green keylight CS ONLY (rather than with OLC) in order to evaluate the impact of its unpredictable food. Interestingly, that comparison reveals a reliable green keylight TRC retardation effect, both in and out of context. This, again, suggests that perhaps there is more to the learned irrelevance effect than may be attributable to context blocking. Mackintosh (1973) observed that CS ONLY pretraining retarded the acquisition of subsequent autoshaping (latent inhibition effect), whereas in Experiment 2, facilitation rather than retardation was engendered by CS preexposure. It is conceivable that the disparity in results may be mediated by differences in procedures which relate directly to the conditioning of contextual cues. Mackintosh provided for the administration of hopper-training in context prior to the administration of the CS ONLY procedure, whereas in the present experiment, hopper-training was administeredfollowing CS preexposure. To the degree that hopper-training establishes the context as an excitatory stimulus, one would expect that subsequent nonreinforced CS preexposure in context would establish the green keylight CS as an inhibitory stimulus (cf. Wagner, 1%9). That is, the latent inhibition effect in context observed by Mackintosh may reflect the inhibitory properties of the green keylight CS following pretraining. The facilitation of acquisition following extensive CS pre-exposure out of context is the typical finding of perceptual learning studies (Anderson, O’Farrell, Formica, & Caponegri, 1969; Anderson, Wolf, & Sullivan, 1969; Lubow, Rifkin, & Alek, 1976) and is consistent with contemporary models of habituation (cf. Lantz, 1973; Lubow, Alek, & Arzy, 1975; Wagner, 1976). The in-context facilitation is, however, completely contrary to the Pavlovian literature on CS preexposure. Why should CS preexposure facilitate rather than retard the acquisition of autoshaping? There are two salient features of autoshaping which distinguish it from alternative Pavlovian procedures. The first is the use of an unrestrained subject in conjunction with a highly localized CS. This encourages the possibility that CS presentations during pretraining will go altogether unnoticed. In fact, during pretraining green keylight CS ONLY subjects

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were often observed to be oriented away from the intelligence panel, thereby depriving themselves of the CS preexposure experience. The use of a localized CS in autoshaping, therefore, may account for the absence of a retardation effect; however, this factor cannot account for the observed facilitation. Perhaps the facilitation is attributable to another unique feature of autoshaping procedures. In autoshaping the subject must be taught to feed from the hopper before acquisition can be initiated. In other words, even for OLC subjects, some degree of US preexposure is required. Such treatment may condition the context and introduce retardation in the OLC group. There is some evidence to support this conjecture. Note that in both experiments the OLC-change groups acquired more rapidly than the OLC-no change groups. The green keylight CS ONLY-no change group also experiences hopper training immediately prior to acquisition; however, extended context preexposure during pretraining would be expected to reduce the conditionability of the preexposed contextual stimuli. In summary, the CS preexposure treatment in autoshaping may be more effective in providing nonreinforced context preexposure than nonreinforced exposure to the keylight CS. Subsequent retardation of context acquisition would be expected to facilitate autoshaping relative to OLCs. There are, of course, alternative interpretations of the context effects observed in these experiments. How might cognitive transfer-of-training interpretations account for the context effect? The accommodation may be relatively simple and straightforward. It is conceivable that the contextual stimuli may act as retrieval cues for the memory of what was learned during pretraining. That is, learning that food is unpredictable may have occurred, but its influence is not observed due to the absence of appropriate retrieval cues. The effectiveness of contextual stimuli as retrieval cues in conditioning-memory experiments has been impressively documented (Hickis, Robles, & Thomas, 1977; Miller, 1972; Spear, 1971, 1973); however, the accommodation is post hoc and dependent upon the attachment of contextual retrieval cues to the memory of higher-order cognitions, rather than simple response tendencies. The possibility exists that these retardation effects are attributable to instrumental responses superstitiously established during pretraining which are incompatible with the autoshaping response (cf. Gamzu, 1971; Gamzu, Williams, & Schwartz, 1973; Wasserman, 1972). Experimental procedures such as those utilized in these experiments confound the conditions of stimulation under which the keypeck was acquired and the conditions of stimulation under which responding was measured. Therefore, it is impossible to separate Pavlovian acquisition effects from effects operative on the performance of the keypeck response, and the context effect may reflect contextual control over incompatible responses, rather than Pavlovian blocking by contextual stimuli.

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There are several problems with the competing response interpretation. First, behaviors that develop as a direct consequence of intermittent US presentations are not incompatible with the topography of the autoshaping response, but, rather, would tend to bring the pigeon into the vicinity of the pecking key and promote orientation toward that stimulus (Staddon & Simmelhag, 1971). Second, the assumption that instrumentally maintained motor responses necessarily retard the acquisition of autoshaping is highly questionable. LoLordo, McMillan, and Riley (1974) observed that pigeons would readily autoshape while concomitantly maintaining a well-learned treadle-press response. Engberg ef al. (1972) explicitly trained an incompatible response (treadle-pressing) for 30 days prior to the initiation of autoshaping. Such training facilitated rather than retarded the acquisition of keypecking. Third, analogous retardation effects in autoshaping have been observed in tests of response reacquisition (Tomie, Hayden, & Biehl, 1979; Tomie, 1980) where incompatible instrumentally maintained superstitious behaviors are unlikely to develop and the reemergence of keypecking is less likely to be determined by mechanistic performance factors. Fourth, similar retardation effects have been observed in alternative Pavlovian conditioning procedures, including human eyelid conditioning (Hobson, 1968; Kimble & Dufort, 1956; Taylor, 1956), nictitating membrane response conditioning in rabbits (Mis & Moore, 1973; Siegel & Domjan, 1971), CER in rats (Baker & Mackintosh, 1979; Kremer, 1971; Randich & LoLordo, 1979; Seligman, 1968), and taste aversion learning in rats (Cannon, Berm&r, Baker, & Atkinson, 1975), where instrumental competing response interpretations are less feasible. To summarize, the present experiments indicate that both the learned laziness and learned irrelevance effects are attenuated by a context change manipulation, the former more convincingly than the latter. There is, in fact, some evidence for context-independent retardation following learned irrelevance pretraining, indicating that the effect is not entirely attributable to blocking by contextual stimuli. This conclusion is supported by Baker and Mackintosh (1979) who overshadowed context control by a forward CS in pretraining and still observed retarded acquisition of CER to a random pretraining CS. The data, therefore, demonstrate the necessity of controlling for contextual influences when evaluating the effects of pretreatment manipulations in transfer designs. REFERENCES Anderson, D. C., O’Farrell, T., Formica, R., & Caponegri, V. Preconditioning CS exposure: Variation in place of conditioning and presentation. Psychonomic Science, 1969, 15, 54-55. Anderson, D. C., Wolf, D., & Sullivan, P. Preconditioning exposure to the CS: Variation in place of testing. Psychonomic Science, 1969, 14, 233-235. Ayres, J. J. B., Benedict, J. O., & Witcher, E. S. Systematic manipulation of individual

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events in a truly random control in rats. Journal of Comparative and Physiological Psychology, 1975, 88, 97-103. Baker, A. G., & Mackintosh, N. J. Preexposure to the CS alone, US alone, or CS and US uncorrelated: Latent inhibition, blocking by context or learned irrelevance? Learning and Motivation, 1979, 10, 278-294. Benedict, J. O., & Ayres, J. J. B. Factors affecting conditioning in the t&y random control procedure in the rat. Journal of Comparative and Physiological Psychology, 1972, 78, 323-330. Blanchard, R., & Honig, W. K. Surprise value of food determines its effectiveness as a reinforcer. Journal of Experimental Psychology: Animal Behavior Processes, 1976, 2, 67-74. Brown, P. L., & Jenkins, H. M. Auto-shaping of the pigeon’s keypeck. Journal of the Experimental Analysis of Behavior, 1968, 11, 1-8. Cannon, D. S., Berman, R. F., Baker, T. B., & Atkinson, C. A. Effect of preconditioning unconditioned stimulus experience on learned taste aversions. Journal of Experimental Psychology: Animal Behavior Processes, 1975, 1, 270-284. Downing, K., & Neuringer, A. Autoshaping as a function of prior food presentations. Journal of Experimental Analysis of Behavior, 1976, 26, 463-469. Engberg, L. A., Hansen, G., Welker, R. L., & Thomas, D. R. Acquisition of key-pecking via autoshaping as a function of prior experience: “Learned laziness”? Science, 1972, 178, 1002-1004. Gamzu, E. Associative and instrumental factors underlying the performance of a complex skeletal response. Unpublished doctoral dissertation, University of Pennsylvania, 1971. Gamzu, E., & Williams, D. R. Classical conditioning of a complex skeletal response. Science, 1971, 171, 923-925. Gamzu, E., & Williams, D. R. The maintenance of key-pecking by stimulus contingent and response-independent food presentations. Journal of the Experimental Analysis of Behavior, 1973, 19, 65-72. Gamzu, E., Williams, D. R., & Schwartz, B. Pitfalls of organismic concepts: “Learned laziness?” Science, 1973, 181, 367-368. Hall, G., & Honig, W. K. Stimulus control after extradimensional training in pigeons: A comparison of response contingent and noncontingent training procedures. Journul of Comparative and Physiological Psychology, 1974, 87, 945-952. Hickis, C. F., Robles, L., & Thomas, D. R. Contextual stimuli and memory retrieval in pigeons. Animal Learning and Behavior, 1977, 5, 161-168. Hobson, G. N. Effects of UCS adaptation upon conditioning in low and high anxiety men and women. Journal of Experimental Psychology, 1%8, 76, 360-363. Kamin, L. J. Predictability, surprise, attention and conditioning. In B. A. Campbell&R. M. Church (Eds.), Punishment and aversive behavior. New York: Appleton-CenturyCrofts, 1969. Kimble, G. A., & Dufort, R. H. The associative factor in eyelid conditioning. Journal of Experimental Psychology, 1956, 52, 386-391. Kremer, E. F. Truly random and traditional control procedures in CER conditioning in the rat. Journal of Comparative and Physiological Psychology, 1971, 76, 441448. Kremer, E. F. The truly random control procedure: conditioning to the static cues. Journal of Comparative and Physiological Psychology, 1974, 88, 700-707. Lantz, A. Effect of number of trials, interstimulus interval and dishabituation during CS habituation on subsequent conditioning in a CER paradigm. Animal Learning and Behavior, 1973, 4, 273-278. LoLordo, V. M., McMiIlan, J. C., & Riley, A. L. The effects upon food-reinforced pecking and treadle-pressing of auditory and visual signals for response-independent food. Learning and Motivation, 1974, 5, 24-41.

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