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Journal of Experimental Psychology: Animal Learning and Cognition - Vol 42, Iss 4



The Journal of Experimental Psychology: Animal Learning and Cognition® publishes experimental and theoretical studies concerning all aspects of animal behavior processes. Studies of associative, nonassociative, cognitive, perceptual, and motivational pro



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Copyright: Copyright 2016 American Psychological Association
 



Asymmetry between excitatory and inhibitory learning.

2016-09-05

Five experiments investigated how learning about the added feature in a feature-positive discrimination or feature-negative discrimination is related to the change in reinforcement rate that the feature signals. Rats were trained in a magazine-approach paradigm with 2 concurrent discriminations between A versus AX and B versus BY. In 2 experiments (1 and 3), X and Y signaled an increase of 0.3 in the probability of reinforcement, from 0.1 to 0.4 (A vs. AX), or from 0.6 to 0.9 (B vs. BY). After extended training, each session included probe test trials in which X and Y were presented alone (Experiment 1) or in compound with another excitatory conditional stimulus (CS), C (Experiment 3). There was no difference in response rate between the 2 types of test trial (X vs. Y; XC vs. YC), consistent with the fact that X and Y signaled the same absolute change in reinforcement. In Experiments 2 and 4, X and Y signaled a decrease of 0.3 in the probability of reinforcement, from 0.4 to 0.1 (A vs. AX) or from 0.9 to 0.6 (B vs. BY). Test trials in which X or Y was presented with C showed that X had greater inhibitory strength than Y, consistent with the fact that X signaled a larger relative change in reinforcement. This was confirmed in Experiment 5, in which X and Y had the same inhibitory strength on test after training in which they signaled the same relative change in reinforcement but different absolute changes (0.3 to 0.1 for A vs. AX; 0.9 to 0.3 for B vs. BY). The results show that excitatory conditioning is linearly related to the increase in reinforcement rate, whereas inhibitory learning is not linearly related to the decrease in reinforcement rate. Implications of this for theories of associative learning are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



The origins of individual differences in how learning is expressed in rats: A general-process perspective.

2016-10-10

Laboratory rats can exhibit marked, qualitative individual differences in the form of acquired behaviors. For example, when exposed to a signal-reinforcer relationship some rats show marked and consistent changes in sign-tracking (interacting with the signal; e.g., a lever) and others show marked and consistent changes in goal-tracking (interacting with the location of the predicted reinforcer; e.g., the food well). Here, stable individual differences in rats’ sign-tracking and goal-tracking emerged over the course of training, but these differences did not generalize across different signal-reinforcer relationships (Experiment 1). This selectivity suggests that individual differences in sign- and goal-tracking reflect differences in the value placed on individual reinforcers. Two findings provide direct support for this interpretation: the palatability of a reinforcer (as measured by an analysis of lick-cluster size) was positively correlated with goal-tracking (and negatively correlated with sign-tracking); and sating rats with a reinforcer affected goal-tracking but not sign-tracking (Experiment 2). These results indicate that the observed individual differences in sign- and goal-tracking behavior arise from the interaction between the palatability or value of the reinforcer and processes of association as opposed to dispositional differences (e.g., in sensory processes, “temperament,” or response repertoire). (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Individual difference in configural associative learning.

2016-10-10

Individuals differ in their ability to acquire associations between stimuli and paired outcomes, an ability that has been proposed to be independent of general metrics of intelligence or memory (e.g., Kaufman, DeYoung, Gray, Brown, & Mackintosh, 2009). The nature of these differences may reflect the type of associative structures acquired during learning, for instance, configuring stimuli to facilitate flexible learning and memory. We test the hypothesis that individuals differ in configural associative learning as distinct from simpler (elemental) stimulus-outcome learning. In Experiment 1 participants were screened for attentional scope and we found that attentional scope predicted configural associative learning that could not be explained simply in terms of differences in strength of associative learning. In Experiment 2, attentional scope was trained resulting in a shift in participants’ ability to learn about subsequent configurations unrelated to the training material. We discuss how the differences between individual learners reflect differences in configuring rather than simply differences in strength or speed of learning. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Testing the boundaries of “paradoxical” predictions: Pigeons do disregard bad news.

2016-09-05

Several studies have shown that, when offered a choice between an option followed by stimuli indicating whether or not reward is forthcoming and an option followed by noninformative stimuli, animals strongly prefer the former even when the latter is more profitable. Though this paradoxical preference appears to question the principles of optimal foraging theory, Vasconcelos, Monteiro, and Kacelnik (2015) proposed an optimality model that shows how such preference maximizes gains under certain conditions. In this paper, we tested the model’s core assumption that a stimulus signaling the absence of food should not influence choice independently of its other properties, such as probability or duration. In 2 experiments, pigeons chose between 2 options: the “informative option” delivered food on 20% of the trials after a 10-s delay, signaled by a “good-news” stimulus, and delivered no food on the remaining 80% of the trials, signaled by a “bad-news” stimulus. The “noninformative option” delivered food after 10 s on 50% of the trials, regardless of the signal shown. In Experiment 1, the probability of the bad-news stimulus was manipulated from 0.80 to 1.00; in Experiment 2, the duration of the bad-news stimulus was increased every time pigeons preferred the informative option, reaching at least 200 s. Consistent with the model’s predictions, pigeons clearly preferred the informative option even when the noninformative option delivered 9 (Experiment 1) and 35 (Experiment 2) times more food. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Chimpanzees can point to smaller amounts of food to accumulate larger amounts but they still fail the reverse-reward contingency task.

2016-09-05

The reverse-reward contingency task presents 2 food sets to an animal, and they are required to choose the smaller of the 2 sets in order to receive the larger food set. Intriguingly, the majority of species tested on the reverse-reward task fail to learn this contingency in the absence of large trial counts, correction trials, and punishment techniques. The unique difficulty of this seemingly simple task likely reflects a failure of inhibitory control which is required to point toward a smaller and less desirable reward rather than a larger and more desirable reward. This failure by chimpanzees and other primates to pass the reverse-reward task is striking given the self-control they exhibit in a variety of other paradigms. For example, chimpanzees have consistently demonstrated a high capacity for delay of gratification in order to maximize accumulating food rewards in which foods are added item-by-item to a growing set until the subject consumes the rewards. To study the mechanisms underlying success in the accumulation task and failure in the reverse-reward task, we presented chimpanzees with several combinations of these 2 tasks to determine when chimpanzees might succeed in pointing to smaller food sets over larger food sets and how the nature of the task might determine the animals’ success or failure. Across experiments, 3 chimpanzees repeatedly failed to solve the reverse-reward task, whereas they accumulated nearly all food items across all instances of the accumulation self-control task, even when they had to point to small amounts of food to accumulate larger amounts. These data indicate that constraints of these 2 related but still different tasks of behavioral inhibition are dependent upon the animals’ perceptions of the choice set, their sense of control over the contents of choice sets, and the nature of the task constraints. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



The role of instructions in perceptual learning using complex visual stimuli.

2016-10-10

Although modeled on procedures used with nonhuman animals, some recent studies of perceptual learning in humans, using complex visual stimuli, differ in that they usually instruct participants to look for differences between the to-be-discriminated stimuli. This could encourage the use of mechanisms not available to animal subjects. To investigate the role of instructions, in 2 experiments, participants were given preexposure to checkerboards that were similar except for the presence of a small distinctive feature on each. For participants instructed to look for differences, performance on a same-different test was enhanced by preexposure in which the critical stimuli were presented on alternate trials—the usual perceptual learning effect. No such effect was found in 2 other preexposure conditions: when participants were told only to look at the stimuli and not explicitly told to look for differences; and when participants were instructed on an alternative task requiring attention to the stimuli. These results indicate a role for a learning process reinforced by success in finding stimulus differences; they challenge previous interpretations of results from studies using complex visual stimuli in the study of perceptual learning. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Evidence for multiple processes contributing to the Perruchet effect: Response priming and associative learning.

2016-10-10

The Perruchet effect constitutes a robust demonstration that it is possible to dissociate conditioned responding and expectancy in a random partial reinforcement design across a variety of human associative learning paradigms. This dissociation has been interpreted as providing evidence for multiple processes supporting learning, with expectancy driven by cognitive processes that lead to a Gambler’s fallacy, and the pattern of conditioned responding (CRs) the result of an associative learning process. An alternative explanation is that the pattern of CRs is the result of exposure to the unconditioned stimulus (US). In 3 human eyeblink conditioning experiments we examined these competing explanations of the Perruchet effect by employing a differential conditioning design and varying the degree to which the 2 conditioned stimuli (CS) were discriminable. Across all of these experiments there was evidence for a component of the CRs being strongly influenced by recent reinforcement, in a way that was not demonstrably influenced by manipulations of CS discriminability, which suggests a response priming mechanism contributes to the Perruchet effect. However, the complete pattern of results and an analysis of the results from previously published studies are also consistent with there being an associative contribution to the effect. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



The extinction procedure modifies a conditioned flavor preference in nonhungry rats only after revaluation of the unconditioned stimulus.

2016-08-15

In 3 experiments rats experienced 2 flavors, each paired with sucrose, in order to establish a conditioned preference to each. One (flavor Fe) was then presented alone (an extinction procedure) prior to a choice test between Fe and the flavor that did not undergo extinction (Fne). Hungry rats showed a preference for Fne over Fe (Experiment 1A), but rats that were not food-deprived showed no effect of extinction when given a choice between Fe and Fne immediately after extinction (Experiment 1B) or after an interval in which reexposure to sucrose was given (Experiment 2). The extinction procedure was not without effect, however, as Fe was preferred over Fne after sucrose had been devalued by pairing with lithium chloride, and Fne was preferred over Fe after a procedure likely to enhance the value of the sucrose (Experiment 3). The explanations considered propose that preference conditioning establishes a range of associations between the flavor and the various properties of sucrose (its nutritional value, its taste, the hedonic reaction it evokes). It is suggested that the form of learning that mediates revaluation effects is sensitive to extinction whereas that responsible for performance on a consumption test is not. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Smelling the goodness: Sniffing as a behavioral measure of learned odor hedonics.

2016-10-10

Pairing an odor and taste can change ratings of the odor’s perceptual and hedonic characteristics. Behavioral indices of such changes are lacking and here we measured sniffing to assess learned changes in odor liking due to pairing with sweet and bitter tastes. Participants were divided on their liking for sweetness, as well as dietary disinhibition (Three-Factor Eating Questionnaire–Disinhibition scale [TFEQ-D]), both of which influence hedonic odor–taste learning. In sweet likers, both sniff duration and peak amplitude increased for the sweet-paired odor. Sniff magnitude decreased for sweet- and quinine-paired odors in sweet-dislikers and sweet likers smelling the quinine-paired odor. In sweet-likers, liking for the sweet-paired odor increased with both TFEQ-D score and hunger, and sniff magnitude with TFEQ-D only. There were no predictors of changes in response to the quinine-paired odor. Brief coexperience of odors with sweet tastes can lead therefore to measurable changes in sniffing, providing a novel behavioral index of odor liking. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



Contextual control of chained instrumental behaviors.

2016-09-05

Recent studies suggest a significant role for context in controlling the acquisition and extinction of simple operant responding. The present experiments examined the contextual control of a heterogeneous behavior chain. Rats first learned a chain in which a discriminative stimulus set the occasion for a procurement response (e.g., pulling a chain), which led to a second discriminative stimulus that occasion-set a consumption response (e.g., pressing a lever) that produced a food-pellet reinforcer. Experiment 1 showed that, after separate extinction of procurement and consumption, each response increased when it was returned to the acquisition context (ABA renewal) or was tested in a new context (AAB renewal). In addition, procurement responding, but not consumption responding, was decreased by changing the context after acquisition. Experiment 2 demonstrated ABA and AAB renewal of procurement and consumption following extinction of the whole chain. This time, the context-switch after acquisition weakened both procurement and consumption. Experiment 3 found that return to the context of the behavior chain renewed a consumption response that had been extinguished separately. Finally, in Experiment 4, rats learned 2 different discriminated heterogeneous chains; consumption extinguished outside its chain was only renewed on return to a chain when it was preceded by its associated procurement response. The results suggest a role for context in the extinction of chained behavior. They also support the view that procurement is influenced by the physical context and that consumption is controlled primarily by the response that precedes it in the chain. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)



A high-fat high-sugar diet predicts poorer hippocampal-related memory and a reduced ability to suppress wanting under satiety.

2016-09-05

Animal data indicate that greater intake of fats and sugars prevalent in a Western diet impairs hippocampal memory and tests of behavioral inhibition known to be related to hippocampal function (e.g., feature negative discrimination tasks). It has been argued that such high-fat high-sugar diets (HFS) impair the hippocampus, which then becomes less sensitive to modulation by physiological state. Thus retrieval of motivationally salient memories (e.g., when seeing or smelling food) occurs irrespective of state. Here we examine whether evidence of similar effects can be observed in humans using a correlational design. Healthy human participants (N = 94), who varied in their habitual consumption of a HFS diet, completed the verbal paired-associate (VPA) test, a known hippocampal-dependent process, as well as liking and wanting ratings of palatable snack foods, assessed both when hungry and when sated. Greater intake of a HFS diet was significantly associated with a slower VPA learning rate, as predicted. Importantly, for those who regularly consumed a HFS diet, though reductions in liking and wanting occurred between hungry and sated states, the reduction in wanting was far smaller relative to liking. The latter effect was strongly related to VPA learning rate, suggestive of hippocampal mediation. In agreement with the animal literature, human participants with a greater intake of a HFS diet show deficits in hippocampal-dependent learning and memory, and their desire to consume palatable food is less affected by physiological state—a process we suggest that is also hippocampal related. (PsycINFO Database Record (c) 2016 APA, all rights reserved)(image)