The effects of stimulus pairings on autistic children's vocalizations: Comparing forward and backward pairings

In a procedure known as stimulus-stimulus pairing (Yoon and Bennett, 2000), the experimenter pairs a target sound (e.g., "bah") with a child's preferred item (e.g., a toy). Even though the stimulus pairings proceed independently of the child's behavior, this procedure has proved capable of increasing imitation of the target sound in developmentally delayed children (Shillingsburg et al., 2015). The underlying behavioral processes remain poorly known, however, and few systematic variations of the basic procedure have been published. In the present experiment, with autistic children as participants, (a) we compared the effects of forward versus backward pairings on the imitation of target sounds, and (b) we evaluated formally the relation between the children's preexisting verbal repertoires and the efficacy of the pairing procedure. As is often reported in the Pavlovian literature, backward pairings promoted lower levels of conditional responding than forward pairings. Also, we found a negative relation between a child's verbal level and pairing efficacy: children with the lower scores on the Behavioral Language Assessment Form (Sundberg and Partington, 1998) exhibited more conditioning. These findings confirm in a single study what has been so far only suspected informally.

A common heritage of behaviour systems

Behaviour systems theory had its beginnings with Nikolaas Tinbergen’s “hierarchical systems”, an aspect of his thinking and writing that he conspicuously left out of his very memorable 1963 manifesto. This starting point has since been developed within psychology, where it has provided numerous advances. Tinbergen’s aspiration for behaviour systems had been principled integration of ethology with physiology, but the bridge among sciences it ultimately provided led to psychology. To an ethology audience, this paper attempts to reintroduce behaviour systems as a part of Tinbergen’s legacy to make accessible the theoretical developments of behaviour systems theory that have occurred outside of ethology over the last several decades. To a psychology audience, the paper serves as a reminder of the ethological origins of behaviour systems. Both sciences and their integration stand to benefit from recognising this point of common heritage.

Neural responses to BEGIN- and END-stimuli of the smoking ritual in nonsmokers, nondeprived smokers, and deprived smokers

Drug-associated stimuli (cues) have a prominent role in addiction research because they are able to provoke craving and relapses. Generally, drug cues are seen as conditioned excitatory stimuli, which elicit drug seeking and usage. However, newer data suggest differential effects for smoking stimuli depending on their stage in the smoking ritual. Specifically, stimuli associated with the terminal stage of smoke consumption (END-stimuli) may evoke reactivity opposite to the reactivity evoked by stimuli associated with the beginning of smoke consumption (BEGIN-stimuli). This fMRI study compared 20 nondeprived smokers with 20 nonsmokers to unravel the influence of smoking-related pictures displaying the beginning (BEGIN-stimuli) and termination (END-stimuli) of the smoking ritual on neural activity in the addiction network. In addition, 20 deprived smokers (12 h deprivation) were investigated to explore the effects of deprivation on the processing of these stimuli. In nondeprived smokers, BEGIN-stimuli reliably activated the addiction network (for example, the ventral striatum, orbitofrontal cortex, and anterior cingulate cortex (ACC)). In contrast, END-stimuli triggered a differential pattern of activations as well as deactivations; deactivations were found in the ventral striatum and the ACC. Deprivation had no clear effect on the responses triggered by BEGIN-stimuli, but affected the reactivity to END-stimuli. Our data clearly suggest that stimuli associated with different stages of the smoking ritual trigger differential neuronal responses. While BEGIN-stimuli generally seem to activate the addiction network, END-stimuli presumably have some inhibitory properties. This new finding might add to a more differentiated understanding of cue reactivity and addiction.

A behavior systems view of the organization of multiple responses during a partially or continuously reinforced interfood clock

We examined how a 50% Pavlovian partial reinforcement (PRF) schedule, versus a 100% continuous reinforcement (CRF) schedule, altered the asymptotic amount and distribution of focal and general search behavior in rats during 48-sec trials with and without a four-segment interfood clock (S1-S2-S3-S4-US). Under CRF, but not PRF, average asymptotic focal search (nosing in the feeder) increased across the last two clock segments (S3 and S4), and more for the clock group than the no-clock group. Locomotor general search peaked in the second clock segment (S2) for the CRF-clock and CRF-no-clock groups and in S3 for the PRF-clock groups. Furthermore, the ratio of general search to maximum focal search was higher for the PRF-clock group than for the CRF-clock group. This pattern of results supports the view that predictable reward presentations temporally organize search states and related responses between food presentations. The relative expression of these responses varies with the predictability and proximity of reward and is more sharply defined in the presence of a clock.

Excitatory backward conditioning in an appetitive conditioned reinforcement preparation with rats

Four experiments were conducted to examine appetitive backward conditioning in a conditioned reinforcement preparation. In all experiments, off-line classical conditioning was conducted following lever-press training on two levers. Presentations of a sucrose solution by a liquid dipper served as an unconditioned stimulus (US) and two auditory stimuli served as conditioned stimuli (CSs); one was paired with the US in either a forward (Experiment 1a) or a backward (Experiments 1b, 2, and 3) relationship, and the other served as a control CS, which was not paired with the US. In testing, each lever-press response produced a presentation of one of the CSs instead of appetitive reinforcers. The response to a lever was facilitated, compared to the response to another lever, when the response produced the backward CS presentation as well as when it produced the forward CS presentation; that is, the backward CS served as an excitatory conditioned reinforcer.

Outcome-specific conditioned inhibition in Pavlovian backward conditioning

In the present experiments, the outcome specificity of learning was explored in an appetitive Pavlovian backward conditioning procedure with rats. The rats initially were administered Pavlovian backward training with two qualitatively different unconditioned stimulus conditioned-stimulus (US-CS) pairs of stimuli (e.g., pellet --> noise or sucrose --> light), and then the effects of this training were assessed in Pavlovian-to-instrumental transfer (Experiment 1) and retardation-of-learning (Experiment 2) tests. In the transfer test, it was shown that during the last 10-sec interval, the CSs selectively reduced the rate of the instrumental responses with which they shared a US, relative to the instrumental responses with which they did not share a US. The opposite result was obtained when the USs (in the absence of the CSs) were presented noncontingently. In the retardation test, conditioned magazine approach, responding to the CSs was acquired more slowly when the stimulus-outcome combinations in the backward and the forward conditioning phases were the same, as compared with when they were reversed. These results are collectively in accord with the view that Pavlovian backward conditioning can result in the formation of outcome-specific inhibitory associations. Alternative views of backward conditioning are also examined.