Statistical decision theory and evolution

Two recent articles by Geisler and Diehl use Bayesian statistical decision theory to model the co-evolution of predator and prey in a simple, game-like environment. The prey is characterized by its coloration. The predator is characterized by the chromatic sensitivity of its visual system and its willingness to attack. The authors demonstrate how the coloration of prey and the perceptual system of the predator co-evolve, converging to a Nash equilibrium for both species.     

Effects of reinforcement magnitude on spontaneous recovery.

Extinction of operant behavior has been associated with a number of undesirable effects. One such effect is the temporary reappearance of behavior after responding appears to be completely extinguished, known as spontaneous recovery. In this report, the occurrence of spontaneous recovery and its attenuation with large amounts of reinforcement were examined during the treatment of disruption.     

Sleep's function in the spontaneous recovery and consolidation of memories

Building on 2 previous studies (B. R. Ekstrand, 1967; B. R. Ekstrand, M. J. Sullivan, D. F. Parker, & J. N. West, 1971), the authors present 2 experiments that were aimed at characterizing the role of retroactive interference in sleep-associated declarative memory consolidation. Using an A-B, A-C paradigm with lists of word pairs in Experiment 1, the authors showed that sleep provides recovery from retroactive interference induced at encoding, whereas no such recovery was seen in several wake control conditions. Noninterfering word-pair lists were used in Experiment 2 (A-B, C-D). Sleeping after learning, in comparison with waking after learning, enhanced retention of both lists to a similar extent when encoding was less intense because of less list repetition and briefer word-pair presentations. With intense encoding, sleep-associated improvements were not seen for either list. In combination, the results indicate that the benefit of sleep for declarative memory consolidation is greater for weaker associations, regardless of whether weak associations result from retroactive interference or poor encoding.     

Greater reinforcement rate during training increases spontaneous recovery

Spontaneous recovery occurs when a previously reinforced and recently extinguished response reemerges over the course of time, often at the beginning of a new session of extinction. Spontaneous recovery could underlie instances of treatment relapse that threaten otherwise effective behavioral interventions for problem behavior. In two experiments, we arranged multiple schedules with pigeons and a human child to assess the effects of different training reinforcer rates on spontaneous recovery. In both experiments, responding was both more resistant to extinction and more likely to relapse following training with greater reinforcement rates upon returning to extinction after time off from extinction testing. A quantitative model based on behavioral momentum theory accounted well for the data, which suggests reexposure to the extinction context following time off during extinction resulted in (1) the failure of extinction learning to generalize, and (2) greater generalization of original learning during training. The present model attempts to quantify theories attributing spontaneous recovery to changes in temporal context.     

Statistical methods for a theory of cue learning

A theory of cue learning, which gives rise to a system of recurrent events in Feller's sense, is analyzed mathematically. The distribution of total errors and sampling distribution of mean errors are derived, and the learning curve is investigated. Maximum likelihood estimates of parameters and sampling variances of those estimates are derived. Likelihood ratio tests of the usual null hypotheses and approximate tests of goodness of fit of substantive hypotheses are developed. The distinguishing characteristic of these tests is that they are concerned with meaningful parameters of the learning process.This research was facilitated by the writer's tenure as Faculty Research Fellow, Social Science Research Council, 1959–1961.     

The relationship between anxiety, fatigue and spontaneous recovery in stuttering

There is apparently no formalized hypothesis regarding the antecedents of spontaneous recovery of stuttering. Since adaptation and recovery appear to be functionally related, antecedents of adaptation have been considered to be antecedent to spontaneous recovery. Two disparate hypotheses of adaptation which have experimental support are the anxiety hypothesis and the fatigue hypothesis. The present study was initiated to investigate the relationship of anxiety and/or fatigue, if any, to spontaneous recovery. Twenty-one subjects (stutterers) participated in four conditions. Each condition consisted of eight oral readings of a passage. The experimental variables were introduced into the respective conditions after the fifth oral reading. They were: (I) no rest, same passage; (II) rest, same passage; (III) no rest, different passage; and, (IV) rest, different passage. Palmar sweat fingerprints of anxiety were taken concurrently with the first thirty seconds of trials one, three, five, six, seven and eight for all conditions. The results of the investigation led to the conclusions that: (1) there was no necessary relationship between a change in the frequency of stuttering and a change in the anxiety level ; (2) the Hullian concepts of reactive and conditioned inhibition appeared to provide a meaningful approach to the question of spontaneous recovery of stuttering behaviour.     

Extinction and spontaneous recovery of a conditioned flavor preference based on calories

After rats were conditioned to prefer a flavor (CS+) paired with sucrose over another flavor (CS−) paired with saccharin, this conditioned flavor preference was extinguished by presenting the CS+ flavor without sucrose. These results were replicated in a second experiment in which spontaneous recovery of the extinguished flavor preference was demonstrated 7, 14, and 21 days after the extinction test. This is the first clear demonstration of the extinction and spontaneous recovery of a conditioned flavor preference based on calories. The implications of these results for our understanding of the mechanism underlying the conditioning of flavor preferences are explored.     

Nicotine vs. ethanol discrimination: Extinction and spontaneous recovery of responding

Studies regarding extinction and spontaneous recovery of the discriminative stimulus effects of drugs are limited. Eight rats were initially trained to discriminate nicotine (0.4 mg/kg) vs. ethanol (800 mg/kg). For four rats, itraperitaneal (IP) administrations of nicotine fifteen minutes prior to fifteen-minute training sessions served as a discriminative stimulus (S^D) for predicting food-reinforced lever pressing (VI-1 min). On other sessions ethanol functioned in predicting nonreinforcement (S^Δ). The stimulus roles of the drugs were counterbalanced for the remaining four rats. S^Δ and S^D sessions alternated quasi-randomly with two daily sessions at 1000 and 1400 hours. Discriminative control was not disrupted following ten extinction sessions under a non-drug/saline condition, but was disrupted following extinction sessions under the original training drugs. Instances of spontaneous recovery (SR) occurred throughout extinction under the drug condtions. There was no evidence for SR two weeks following extinction, but partial recovery four weeks following the final extinction phase. Contextual status (context renewal) had neither a restorative or disruptive impact on extiguished or discriminated responding, respectively. Theser results support and extend the limited number of other studies by demonstrating extinction and spontaneous recovery of responding discriminated bytwo distinct drugs. Some theoretical interpretations regarding history effects and training in the context of drug discrimination are entertained.