Resistance to extinction versus extinction as discrimination

The hypothesis that response strength might be measured by persistence of responding in the face of extinction was discredited in the 1960s because experiments showed that responding persists longer following intermittent reinforcers than following continuous reinforcers. Instead, researchers proposed that the longer persistence following intermittent reinforcers arises because intermittent reinforcement more closely resembles extinction—a discrimination theory. Attention to resistance to extinction revived because one observation seemed to support the persistence hypothesis: Following training on a multiple schedule with unequal components, responding usually persisted longer in the formerly richer component than in the formerly lean component. This observation represents an anomaly, however, because results with single schedules and concurrent schedules contradict it. We suggest that the difference in results arises because the multiple-schedule procedure, while including extensive training on stimulus discrimination, includes no training on discrimination between food available and food unavailable, whereas comparable single- and concurrent-schedule procedures include such training with repeated extinction. In Experiment 1, we replicated the original result, and in Experiment 2 showed that when the multiple-schedule procedure includes training on food/no-food discrimination, extinction following multiple schedules contradicts behavioral momentum theory and agrees with the discrimination theory and research with single and concurrent schedules.     

Overtraining, extinction and shift learning in a concurrent discrimination in rats

Two experiments examined the influence of overtraining on the reversal of a concurrent discrimination. After rats are trained to criterion on two different discriminations in the same apparatus, the reversal of one of these proceeds more rapidly than when both are reversed. If the reversal is conducted after overtraining on the original discriminations, then the opposite pattern of results is observed. That is, learning about the reversal of both discriminations is more rapid than when only a single discrimination is reversed. Experiment 1 replicated this effect and suggested that it is not caused by differences in the rate of extinction during reversal learning. In order to test a cue-association account for these findings, Experiment 2 examined the effect of exchanging the negative stimuli of a concurrent discrimination. This manipulation had a disruptive influence on performance, but only when subjects were not overtrained on the original discrimination.     

Optional shift behavior as a function of age and dimensional dominance

An optional reversal-nonreversal shift task for which the relevant color or form cues were either dominant or nondominant was presented to 320 Ss, 6 through 20 years of age. Dominance, as defined in terms of relative cue similarity, was related to initial learning and shift behavior for kindergarten and third-grade Ss; but not for sixth-grade and college Ss. The speed of initial learning and percentage of reversal shifts was related to age when the nondominant dimension was relevant. There were no developmental differences when the dominant dimension was relevant.     

Acquisition and extinction in autoshaping

C. R. Gallistel and J. Gibbon (2000) presented quantitative data on the speed with which animals acquire behavioral responses during autoshaping, together with a statistical model of learning intended to account for them. Although this model captures the form of the dependencies among critical variables, its detailed predictions are substantially at variance with the data. In the present article, further key data on the speed of acquisition are used to motivate an alternative model of learning, in which animals can be interpreted as paying different amounts of attention to stimuli according to estimates of their differential reliabilities as predictors.     

Local contour characteristics as determinants of pattern discrimination

Subjects were required to discriminate complex random polygons which had the same global shapes but differed in local contour characteristics. Discrimination was most often successful when local contour features comprised a few long line segments or when they were relatively complex. Local contour features of intermediate sized elements and intermediate complexity played a smaller role in discrimination. Presentation time and interstimulus interval effects, and their interaction were observed. A two-factor explanation was offered for the effect of the contour variable.     

Ideological beliefs as determinants of discrimination in positive and negative outcome distributions

Social identity theory proposes that discrimination contributes favourably to group members' social identity. In minimal group paradigm (MGP) studies involving positive outcome distributions (e.g. money), discrimination is associated with a more positive social identity. But studies on the positive‐negative asymmetry effect show that categorization leads to less discrimination when negative (salary cuts) than when positive outcomes (salary increases) are distributed. Using structural equation modelling, this study (N = 279) tested whether discrimination involving negative outcome distributions could contribute as much to group members' positive social identity as discrimination on positive outcomes. The study also tested if ideological beliefs (i.e. social dominance orientation, authoritarianism), measured one month before the MGP experiment, could predict positive and negative outcome discrimination. While the fit of the hypothesized model was adequate, only social dominance orientation predicted both positive and negative outcome discrimination. Also, discrimination on positive outcomes but not on negative ones contributed to positive social identity. Copyright © 2004 John Wiley & Sons, Ltd.     

Acquisition and extinction of signaled avoidance as a function of intermittent reinforcement

Signaled, shuttle-box avoidance responding in female rats of the Fischer₃₄₄ strain was examined as a function of four separate contingencies of intermittent reinforcement. In Experiment 1, when avoidance responses during acquisition were reinforced 25% of the time with prompt CS termination, animals responded equally often during acquisition and significantly more often during extinction than animals who received such reinforcement on a 100% schedule. Similar results were found under a trace procedure in Experiment 2 when avoidance responses were reinforced 25% of the time with informational feedback stimuli. In contrast, during Experiment 3, when animals were shocked on only 25% of the trials on which they failed to respond, the level of avoidance responding during both acquisition and extinction was significantly less than it was when animals were shocked on a 100% schedule. Comparable results were found in Experiment 4 when avoidance responses during acquisition averted shock on only 25% of the trials. Thus, intermittent reinforcement contingencies involving response-contingent feedback stimuli and shock have differential effects on avoidance responding during both acquisition and extinction trials under the signaled avoidance procedure.     

Startbox-goalbox confinement durations as determinants of self-punitive behavior

Two levels of confinement duration (5 or 60 sec) in either startbox or goalbox were factorially combined with presence or absence of shock during extinction of a runway escape response in a self-punitive paradigm under a spaced-trials procedure. All groups were equated for amount and temporal spacing of handling before and after each trial. Shocked rats were more resistant to extinction than nonshocked rats only when startbox confinement was short. When startbox confinement was long, shock facilitated extinction. Long goalbox confinement enhanced running speed for shocked rats, but only in the presence of shock. It was suggested that duration of startbox confinement affects strength of conditioned fear, with long confinement leading to its extinction.