The influence of partial reinforcement on serial autoshaping with pigeons

The effect of partial reinforcement on the rate of responding during the first element of a serial compound was investigated using autoshaping in pigeons. Experiment I employed the illumination of a response key by two different colours as the elements of the compound. Responding during the first element was faster when this stimulus was intermittently paired with the second element and the unconditioned stimulus than when a continuous reinforcement schedule was employed. Experiment II demonstrated that this effect of partial reinforcement is unaffected by maniuplating the associative strength of the second element at the outset of compound conditioning. A similar effect of partial reinforcement was also found in Experiment III which used a tone as the first element of the serial compound.     

The associative relation underlying autoshaping in the pigeon

Fifteen pigeons were exposed to either response-independent or response-dependent schedules of water reinforcement, whereby water was injected directly into the unrestrained pigeons' mandibles. Key-contact responses were released by a lighted key correlated with water, but not by a lighted key uncorrelated with water. A negative response-reinforcer contingency suppressed autoshaped key-contact responses, resulting in responding directed away from the lighted key. In all pigeons, water injected directly into the mandibles elicited a consummatory fixed-action pattern of “mumbling” and swallowing. The lighted key correlated with water released a broader set of both appetitive and consummatory responses: approach to the lighted key, “bowing”, “rooting”, “mumbling”, and swallowing. Key-contact responses were “rooting” and “mumbling” motions of the beak on the surface of the key. Views of autoshaping based on stimulus substitution or stimulus surrogation do not fully explain the origin of autoshaped responses not previously elicited by the reinforcer. The present findings are consonant with views of conditioning that emphasize the large degree of biological pre-organization in conditioned response patterns, and the importance of associative factors in the control of such patterns.     

Partial reinforcement and autoshaping of the pigeon's key-peck behavior

Pigeons were exposed to continuous and partial reinforcement (25%) schedules in an autoshaping procedure. The number of trials and/or pairings per session were equated across two factorial group sets and all groups were trained for a fixed total number of acquisition trials (192). When acquisition was analyzed as a function of reinforcements delivered, the groups receiving fewer number of trials per session acquired the response faster, independently of the percentage of reinforced trials. Moreover, the number of reinforcements to satisfy an acquisition criterion was a monotonic function of the number of trials per session but not of the schedule. The results are discussed in relation to the neocontinuity and the scalar expectancy theories.     

A comparison of the effects of partial reinforcement schedules using a within-subject serial autoshaping procedure

Three experiments, each using a single group of pigeons, are reported. In Experiment 1 subjects were initially trained with two stimuli, one of which was always followed by food, the other being reinforced according to a 50% partial reinforcement schedule. Subsequently a serial procedure was adopted in which an additional stimulus, C, was consistently followed by the partially reinforced CS. A second additional stimulus, A, was followed on half of its occurrences by the continuously reinforced CS, its remaining presentations being followed by nothing. The rate of autoshaped keypecking was substantially greater during A than during C. In the remaining experiments subjects received first-order conditioning with a single stimulus that was either partially (Experiment 2) or continuously (Experiment 3) reinforced. The stimuli A and C were then again introduced for serial autoshaping. Stimulus A was occasionally paired with the CS and occasionally followed by nothing, whereas stimulus C was always followed by the CS. As in Experiment 1, the rate of responding during A was greater than during C. It is proposed that one influence on the rate of autoshaped keypecking during a CS is the accuracy with which the immediate consequences of that CS are predicted.     

The role of local context in autoshaping

Three experiments used an autoshaping procedure with pigeons to examine the effects of nonreinforced, nontarget stimuli (ITI-fillers) during the intertrial interval on responding to a reinforced target CS. Experiment 1 replicated a previous demonstration that an ITI-filler that occupied a substantial portion of the ITI attenuated responding to the target CS relative to a group trained with a similar ITI but lacking the ITI-filler. Experiment 2 found that the superiority of responding typically found with a long ITI relative to a short ITI, that is, the trial-spacing effect, can be reversed by imposing a filler stimulus during the ITI in the former condition. Experiment 3, using a within-subject design, found that when one background stimulus condition occupied a majority of the interreinforcement interval, pairings of one target CS with reinforcement that were embedded within this background condition, that is, a long duration local context occurred for this CS, yielded better performance that a second, reinforced, target CS paired with reinforcement in the shorter duration background condition. These results confirmed predictions derived from a local context view of cycle time. Comparator theories of classical conditioning require incorporation of this notion into their conceptualization of effective cycle time in order to explain the present findings.     

The roles of event contingencies and reinforcement in human autoshaping and omission responding

Four experiments were conducted to test those features deemed to play an important role in the acquisition and/or maintenance of autoshaping and omission responding with human subjects, viz., event contingencies, reinforcement, stimulus generalization, the type of CS employed, conditioned reinforcement, and response topography. One important aspect of these studies is that the boundary conditions were made to resemble those pertaining to the majority of nonhuman animal studies, i.e., magazine training followed by paired CS-US presentations. The results demonstrated the importance of CS-UR or, alternatively, CS-US contiguity together with generalization and a response-reinforcer contingency for autoshaped response initiation and maintenance, respectively. The conditioned reinforcing effect of CS offset appears to play a part in generating and maintaining some responding during omission training, especially during a response-terminated CS procedure. Similar response topography was observed when the form of the UR was compared to that of the CR or autoshaped response. Taken as a whole the results of these experiments with humans are directly comparable to results previously reported using a wide variety of nonhuman animals.     

The role of context in intertrial interval effects in autoshaping

Two experiments evaluated the role of differential conditioning of the context in mediating the effect of intertrial interval (ITI) in autoshaping. In Experiment 1 pigeons were given acquisition with two keylights, each presented in a particular context. A given keylight/context combination had associated with it either a short (10-sec) or a long (2-min) ITI. Acquisition was more rapid with the long ITI. Tests with those keylights in a common third context indicated that the longer ITI had resulted in greater conditioning. On the other hand, pigeons trained on keylights with mixed ITIs in a third context evoked more responding when they were tested in the short ITI context compared with the long ITI context. That suggests that a context with a history of a short ITI enhances performance. In Experiment 2, two keylights were initially conditioned with mixed ITIs and then extinguished in different contexts under different ITI lengths. Extinction was more rapid for the keylight presented with a short ITI. That difference persisted when the keylights were tested with mixed ITIs in a common third context, suggesting a difference in associative strength of the keylights. The results are interpreted in terms of differential context conditioning resulting in differences in learning about the keylight.     

The effects of reinforcement upon the prepecking behaviors of pigeons in the autoshaping experiment

The autoshaping procedure confounds the effects of pairing a keylight and food with the effect of adventitious food reinforcement of responses that typically occur before the pecking response. In Experiment I, acquisition of the orientation to the key, the approach toward the key, and the peck at the key were systematically monitored. Orientations to the key and approaches toward the key frequently occurred in contiguity with food presentation before peck acquisition. In Experiment II, a negative contingency procedure was used to assess the sensitivity of the approach toward the key to its consequences. When the approach toward the key resulted in nonreinforcement, the probability of occurrence of that response decreased to zero despite repeated light-food pairings. In Experiment III, peck probability was shown to be determined during the approach toward the key by the presence of stimuli that had previously been either paired or nonpaired with food. In Experiment IV, it was shown that the effects of the stimulus present during the approach toward the key were not due solely to the effects of pairing that stimulus with food. Autoshaped key pecking appears to be determined by the interacting effects of stimulus-reinforcer and response-reinforcer variables upon orientations to, approaches toward, and pecks at the lighted key.     

The role of autoshaping in cooperative two-player games between starlings

We report a study of the behavior of starlings in laboratory situations inspired by the “prisoner's dilemma.” Our purpose is to investigate some possible mechanisms for the maintenance of cooperation by reciprocity and to investigate the process of autoshaping at a trial-by-trial level. In Experiment 1, pairs of starlings housed in adjacent cages played a discrete-trial “game” in which food could be obtained only by “cooperation.” In this game, pecking at a response key eliminated the opportunity to obtain food but produced food for the partner. If neither bird pecked, neither had the opportunity to obtain food in that trial. Some level of cooperation persisted for several sessions whether the birds had been pretrained for a high or low probability of pecking at the key. The probability of a cooperative response was higher after trials in which the partner responded (and a reward was obtained) than after trials in which neither bird responded (and no reward was obtained), but the probability of a response was even higher after trials in which the same bird had responded, even though no reward was obtained by the actor in these trials. This behavior did not require visual presence of another player, because similar results were obtained in Experiment 2 (a replicate of Experiment 1 in which the members of the pair could not see each other) and in Experiment 3, a game in which each starling played with a computer responding with “tit for tat.” Using an omission schedule, in which food was given in all trials in which the bird did not peck, Experiment 4 showed that pecking could be maintained by autoshaping. In this experiment, overall probability of pecking decreased with experience, due to a drop in the tendency to peck in consecutive trials. The probability of pecking in trials following a reinforced trial did not decrease with experience. An implementation of the Rescorla–Wagner model for this situation was capable of reproducing molar, but not molecular, aspects of our results. The results violate the predictions of several game-theoretical models for the evolution of cooperation, including tit for tat, generous tit for tat, and the superior win-stay-lose-shift.     

Predictive accuracy and not reduction in uncertainty influences responding during serial autoshaping

Two experiments with pigeons employed a serial autoshaping design in which food was presented on every trial, and the initial element was of variable duration. When the first element was followed randomly by one stimulus of fixed short duration and another stimulus of fixed long duration, then it elicited a relatively high rate of responding. But when the second elements were of equal mean durations, whether fixed or variable, then responding during the first element was relatively slow. Two explanations for these findings were considered. One stipulates that the rate of responding during a stimulus is related to its predictive accuracy, the other stipulates that responding is influenced by the reduction in uncertainty that follows the offset of a stimulus. It is argued that the evidence favours the first of these alternatives.     

Linking associative and serial list memory: Pairs versus triples

Paired associates and serial list memory are typically investigated separately. An "isolation principle" (J. B. Caplan, 2005) was proposed to explain behavior in both paradigms by using a single model, in which serial list and paired associates memory differ only in how isolated pairs of items are from interference from other studied items. In the present study, 2 experiments identify a critical dissociation between the 2 paradigms, challenging this unified account. Specifically, forward and backward probes were highly correlated for pairs and less so for short lists (triples). The authors asked whether the isolation principle could quantitatively accommodate this type of dissociation. A simulation confirmed that a single model incorporating the isolation principle can adequately explain this and other dissociations, supporting the common processes view.     

Large visuospatial sex difference in line judgment: possible role of attentional factors

This article describes a large sex difference on a new, group-administered visuospatial task, the Judgment of Line Angle and Position (JLAP) test, and investigates the role of attentional factors in the difference. On the JLAP, adapted from a neuropsychological task (Benton et al., 1983), participants evaluate spatial attributes of lines. Study 1: College males (N = 48) outperformed females (N = 80), resulting in a large effect for sex (d = 0.85). Errors were more common on oblique (vs horizontal or vertical) lines, especially for females. Study 2: Task attributes were manipulated (N = 33 males and 36 females) to study the role of attentional factors. Findings suggest that males are more likely than females to normally attend to and be aided by geometrical reference cues.     

The role of attentional set on attentional cueing and inhibition of return

When people know what critical feature will define a target for a block of trials, only cues that share a critical feature with targets will capture attention. This result is taken to mean that attentional control settings play a role in target identification. To examine the validity of the attentional control settings hypothesis while controlling for potential sensory artifacts, the first experiment compared conditions in which the critical target features were either blocked or randomized. The results indicated that all cues captured attention in the random conditions, but only cues that matched targets captured attention in the attentional set condition. The second experiment used the same two conditions to examine the effect of attentional set on inhibition of return (IOR). No differences were found between the blocked and random conditions, indicating that attentional set did not impact the IOR effects. Overall, the results indicate that (1) the previous findings of attentional set effects were not due to an artifact of the method, and (2) attentional set influences and early occurring attentional cueing effects but not later-occurring IOR effects.     

The role of associative history in models of associative learning: A selective review and a hybrid model

Associative learning theories strive to capture the processes underlying and driving the change in strength of the associations between representations of stimuli that develop as a result of experience of the predictive relationships between those stimuli. Historically, formal models of associative learning have focused on two potential factors underlying associative change, namely processing of the conditioned stimulus (in terms of changes in associability) and processing of the unconditioned stimulus (in terms of changes in error). This review constitutes an analysis of the proper role of these two factors, specifically with regard to the way in which they are influenced by associative history (the prior training undergone by cues). A novel “hybrid” model of associative learning is proposed and is shown to provide a more satisfactory account of the effects of associative history on subsequent learning than any previous single-process theory.     

The role of uncertainty in attentional and choice exploration

Psychonomic Bulletin & Review - The exploitation-exploration (EE) trade-off describes how, when making a decision, an organism must often choose between a safe alternative with a known pay-off,...     

Recognition memory and attentional selection: serial scanning is not enough

In two experiments, using memory sets of up to 10 letters, the response competition paradigm was employed to investigate the extent to which extraneous visual stimuli interfere with or affect the process of memory search. It was assumed that if selective attention could exclude the effect of noise letters from a Sternberg-type memory comparison process, then there would be an increase in intercept for the reaction time-set size functions but no increase in slope. This result was obtained. However, a large difference in response times to both positive and negative set targets was found when the accompanying noise letters indicated a competing response, as opposed to when they indicated the same response as the target. This implies rapid identification of the nature of both target and noise, independent of a serial comparison process. A modification of a dual process model (Juola, Fischler, Wood, & Atkinson, 1971) in which stimuli activate a familiarity value independent of memory search was suggested to account for these results.