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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 27, Issue 4, 2014

Issue cover

Research Article

The frequency and nature of allocare by a group of belugas (Delphinapterus leucas) in human care

The care of offspring by non-parental caregivers, or allocare, is common across many taxa.  Several functions of allocare have been proposed, including opportunities to rest or forage for the mother, experiences to learn about caring for young animals for naïve females, or additional nourishment and protection for the offspring.  Belugas, like many cetaceans, display allocare.  However, the frequency and contexts in which allocare occurs have not been studied extensively.  The purpose of the current study was to document the frequency of allocare in a group of belugas in human care that steadily increased in its number of offspring over a period of four years.  The results suggested that allocare did not occur as frequently as mother-calf swims and occurred when adult females without calves were available in the social grouping.  Additionally, certain allocare partners seemed to be preferred by specific mother-calf pairs.  The results also indicated that the calf may play a more active role in the selection of an allocare partner than previously acknowledged.  This study supports the importance of social composition when young offspring are present.

Special Issue Introduction

Operant/Classical Conditioning: Comparisons, Intersections and Interactions The 2014 Winter Conference on Animal Learning and Behavior Focus and Research Seminar Sessions

The Keynote Speaker at Winter Conference on Animal Learning and Behavior (WCALB) 2014 was Dr. Björn Brembs whose address was titled, Pavlovian and Skinnerian Processes Are Genetically Separable.  The essence of the address, that describes the research on which Dr. Brembs based this conclusion, is described below.  Articles in this issue representing the related Focus Session include:  The Many Faces of Pavlovian Conditioning by Dr. Jozefowiez, Pavlov + Skinner = Premack by Dr. Killeen, Evocation of Behavioral Change by the Reinforcer is the Critical Event in Both the Classical and Operant Procedures by Dr. Donahoe, On Choice and the Law of Effect by Dr. Staddon, Response-Outcome versus Outcome-Response Associations in Pavlovian-to-Instrumental Transfer:  Effects of Instrumental Training Context by Gilroy, Everett and Delamater, and The Instrumentally-Derived Incentive-Motivational Function by Dr. Weiss.  As a whole, they attempt to increase our contact with, and get at the essence of, what is actually happening with these operant and classical contingencies in the laboratory and nature.  The Research Seminar Session revealed the current tendency for explanations of behavior to be reduced to physiology, neuroscience, and genetics.  However, anti-reductionists saw shortcomings in this approach.  They recommended an interconnected holistic approach which shifts the focus away from the structure of discrete behaviors and toward examining the environment in which the behavior occurs and the consequences produced.  The distinction between structural and functional analysis points to a difficulty of integrating facts about behavior with other levels of analysis that requires our attention.


Special Issue

The Many Faces of Pavlovian Conditioning

Is Pavlovian conditioning the same thing as Pavlovian conditioning? Though that question seems tautological, this article shows that it is not, because Pavlovian conditioning has at least three different meanings: Pavlovian conditioning is (1) a procedure, (2) the learning phenomenon observed in that same procedure and (3) the learning process explaining the phenomenon observed in that procedure. If we look at this third meaning from an evolutionary point of view, it seems extremely unlikely that a single Pavlovian conditioning process is responsible for learning in all procedures classified as Pavlovian conditioning -- a conclusion that supported by behavioral and neural data. In the end, it seems that it might be better to drop the term Pavlovian conditioning to designate a learning process and to stop the quest for a single process explaining all Pavlovian learning. Instead, it would be more fruitful to understand under which condition a particular model of Pavlovian learning holds. The same conclusion applies to other research field in the psychology of learning, notably operant conditioning and statistical learning.

Evocation of Behavioral Change by the Reinforcer is the Critical Event in both the Classical and Operant Procedures

By definition, in a Pavlovian (classical) procedure a stimulus is presented prior to an eliciting stimulus (reinforcing stimulus) in an operant procedure a response occurs prior to the reinforcer. In spite of the different contingencies implemented by the two procedures, some behavior necessarily precedes the reinforcer in the Pavlovian procedure and some stimulus necessarily precedes the reinforcer in the operant procedure. If conditioning depends on the momentary relation of environmental and behavioral events to a reinforcer, then the two procedures must begin by engaging a common conditioning process. The cumulative effects of that common process are different, however, because of differences in the frequency with which specific environmental and behavioral events are contiguous with the reinforcer (and its elicited response). The view that the critical reinforcing event is the evocation of a change in ongoing behavior evoked by the eliciting stimulus provides the basis for an interpretation of the conditioning process that encompasses the effects of both procedures.

Pavlov + Skinner = Premack

Behavior is a sequence of actions.  Premackian conditioning occurs when one of those actions permits an animal to engage in more biologically potent positive responses—reinforcement—or forces them to engage in less positive (or negative) responses —punishment.  Signals of the transition from one class of actions to another focus the instrumental responses in the first class and inform the contingent responses in the second class.  The signals may be innate (USs) or learned (sign-learning); excitatory (leading to more positive actions) or inhibitory (leading to less positive actions).  The potency of an action has phylogenetic origins, but may be conditioned by proximity to more potent responses, such as consummation of a reinforcer.  With practice instrumental responses may take on increased strength, and in some cases become motivationally autonomous—become habits.  Stimuli or responses that signal the availability of more positive actions may become incentive motivators that animals will approach.  Discriminative stimuli do not have intrinsic value as reinforcers, but only the value derived from the responses that they release.  These forces bend an animal’s trajectory through its stimulus-action-time context into a path that leads more directly to positive actions.  The association of actions (conditioned responses, operants, and observing responses) with actions of different potency (ultimately unconditioned responses or consummatory behavior) is the primary association in Premackian conditioning.  All other types of conditioning may be interpreted as instances of such Premackian conditioning.

On Choice and the Law of Effect

Cumulative records, which show individual responses in real time, are a natural but neglected starting point for understanding the dynamics of operant behavior.   To understand the processes that underlie molar laws like matching, it is also helpful to look at choice behavior in situations such as concurrent random ratio that lack the stabilizing feedback intrinsic to concurrent variable-interval schedules.  The paper identifies some basic, nontemporal properties of operant learning: Post-reinforcement pulses at the beginning of FI learning, regression, faster reversal learning after shorter periods, and choice distribution on identical random ratios at different absolute ratio values.  These properties suggest that any operant-learning model must include silent responses, competing to become the active response; and response strengths that reflect more than immediate past history of reinforcement.  The cumulative-effects model is one that satisfies these conditions.

Response-Outcome versus Outcome-Response Associations in Pavlovian-to-Instrumental Transfer: Effects of Instrumental Training Context

One experiment with rats used Pavlovian-to-instrumental transfer (PIT) tests to explore potential competitive interactions between Pavlovian and instrumental processes during instrumental learning. Two instrumental response-outcome relations (e.g., left lever – grain pellets, right lever – sucrose pellets) were first trained in distinct contexts for one group of rats (Group Differential) or in each of two contexts for a second group (Group Non-Differential).  Both of these groups then received training with two Pavlovian stimulus-outcome relations in a third experimental context.  Selective PIT tests conducted in both the Pavlovian and instrumental contexts revealed greater selective PIT in Group Non-Differential than in Group Differential subjects.  This result is discussed in terms of the roles played by context-outcome, response-outcome, and outcome-response associations during instrumental learning. The results further help us understand the nature of Pavlovian-instrumental interactions in specific PIT tasks.

The Instrumentally-Derived Incentive-Motivational Function

Though differential reinforcement, a discriminative stimulus (S D ) acquires two properties.  The operant contingency is responsible for the S D s response-discriminative property.  However, as stimulus control develops an S D also acquires incentive-motivational properties through its association with reinforcement changes.  A systematic series of experiments are described that breaks the usual co-variation of response and reinforcement rates in most discriminative operant situations.  In three groups, S D s (a tone and a light) occasioned steady moderate lever pressing in rats that ceased when neither S D was present.  Probably of reinforcement in these S D s, relative to when both were off, was systematically manipulated to make them incentive-motivationally excitatory, neutral or inhibitory.  In each S D , for the “excitatory” group reinforcement (food) probability increased from 0 to 100%, for the “neutral” group it was unchanged and for the “inhibitory” group it decreased from 100 to 0%.  Although behaviorally indistinguishable in training, a stimulus-compounding assay revealed that tone-plus-light tripled response rate in the incentive-excitatory group, doubled rate in the incentive-neutral group and didn’t increase rate in the incentive-inhibitory group – producing the instrumentally derived incentive-motivational function for the first time.  This is discussed context of two-process learning theory, a functional analysis of transfer-of-control research plus how the response-discriminative and incentive-motivational properties acquired by an S D contribute to the stimulus control of behavior.