Nest material and food as reinforcers for fixed-ratio responding in mice

Three experiments investigated the importance of operant-reinforcer distance as a factor affecting continuous reinforcement (CRF) and fixed-ratio (FR) performance in mice, with nest material and food as reinforcers. In Experiment 1, nest material (paper strips) was presented on a series of FR schedules of increasing size, with the operandum located as close as possible to the reinforcer dispenser. Subjects compensated for increases in FR size by proportionately increasing their response output, but ratio strain occurred at low FR values. In Experiment 2, response rate was found to be inversely related to operant-reinforcer distance on a CRF schedule with nest material as reinforcer. In Experiment 3, food was presented on a series of FR schedules at two levels of deprivation, and with three operant-reinforcer distances. Operant-reinforcer distance was found to affect CRF response rate, degree of compensation for increases in FR size, and occurrence of ratio strain, but only when deprivation level was low. The results support the view that nest material and food share fundamentally similar reinforcing properties, but that nest material is a weaker reinforcer under normal test conditions.     

Age related changes in the effectiveness of name and visual codes in recognition memory

In the first of three studies college, third grade, and kindergarten Ss were able to determine that two stimuli presented 700 msec apart were the same more quickly if they were visually identical than if they shared the same name. If 3000 msec elapsed between stimulus presentations third grade and college Ss responded at the same rate in making both types of matches, whereas kindergarten Ss appeared to continue to respond more quickly in making visual matches. Study II was an unsuccessful attempt to replicate the kindergarten finding. A warning signal, presented 500 msec prior to the second stimulus, reduced RTs at both interstimulus intervals, but no significant differences in making visual and name matches occurred. In Study III first-graders, responding either with or without a warning signal, were found to respond like the older Ss in Study I. The warning signal again reduced RT at both intervals. The results suggest that Ss across a wide age range are able to use the visual properties of a stimulus for only a very brief period as the basis for making matching judgments.     

Threats and promises: Reputational consequences and transfer of credibility

This study was designed to investigate the reputational consequences of making threats and promises and how they affect subsequent credibility. Eighty-eight high school girls were given predetermined information about the past behavior of their pairmates prior to receiving influence attempts from them. Each first learned that her pairmate had (1) threatened or promised in the past and then learned whether she had (2) fulfilled or failed to fulfill her threat or promise. The subject herself then received a threat or promise from her pairmate. As anticipated, threateners were viewed less favorably than promisers. These impressions were maintained when it was learned that commitments had been fulfilled, but altered decidedly when it was learned that they had not. Credibility or lack of it was found to generalize from threats to promises and from promises to threats only under some conditions. It was concluded that the fit between existing impressions and proclaimed future activity, not a person's record for past reliability, is often the critical determinant of whether or not she is judged to be credible.     

Retrieval processes in recall

A reaction time (RT) paradigm was developed to study retrieval processes in paired associate (PA) recall. Prior to the experimental session, subjects learned lists of PAs (varying in length from three to 24 pairs); during the experimental session, subjects' RT to say the response word from the onset of a visually presented stimulus word was measured. The implications of several classes of retrieval models were discussed in the context of this paradigm. The shape of the RT-list length function, practice, and sequential effects were all of interest in distinguishing among models. Four experiments were reported which were designed to (1) establish the baseline effects in this paradigm, (2) determine which of these effects should be attributed to the retrieval stage of processing, and (3) investigate the effect of semantic memory in this task. Results suggest that simple serial scanning models are inadequate to handle the data from this task. Strength, direct-access, or parallel processing models, on the other hand, seem to capture the qualitative effects present in our experiments. When a strength model was formalized and fit to the data from Experiment I, it was found that a two-trace version gave good quantitative fits while a one-trace version did not, suggesting that both short- and long-term memory independently contribute in this task.     

When what is said is important: A comparison of expert and attractive sources

Ninety-eight female subjects were presented with a statement made by an attractive or an expert source suggesting that people should sleep less than the usual eight hours. For approximately half of the subjects the source gave a simple statement of opinion, for the other half six separate supporting arguments were also presented. As predicted the manipulation of number of arguments provided had more influence on the effectiveness of the expert than the attractive source. Results were interpreted as supporting the hypothesis that quite different dynamics underly the persuasive power of attractive and expert individuals.     

Using conjoint-measurement models to investigate a theory about probabilistic information processing

A theory of how opinions are formed and revised on the basis of probabilistic evidence is presented. The decision maker is viewed as a limited information processor who attends to the dimensions of a sample of equivocal information in a sequential fashion, beginning with the most salient dimension and continuing in decreasing order of salience. The contribution of each dimension level to the final opinion depends on the strength of association between that level and each of the two hypotheses under consideration. This theory is represented formally as an additive-difference model, various special cases of which correspond to other algebraic models in the literature. Two of the special cases were empirically investigated under varying levels of experience and payoffs, using the techniques of conjoint-measurement theory and ordinal data from individual subjects. The data provided reasonably good support for the models under all conditions investigated, and in addition showed interesting effects on salience and on processing of the independent variables.     

The effect of frustrative nonreward on the attractiveness of the omitted reward

Two experiments were performed to test the hypothesis that omission of a previously received reward is followed by greater motivation to obtain that specific reward, as compared with the case where the reward had been present. In Experiment 1, experimental rats regularly received food rewards (R_a) at one goal, followed by a choice between food and milk (R_b). Control animals received the same choice without food preceding it. Reward magnitudes were manipulated so as to produce a preference for R_b, and additional forced trials were given each day to equalise experience of the two rewards. In the test phase both groups received trials with R_a present (R) or absent (N) at the first goal. The experimental Ss shifted their choice towards R_a on N trials; the controls did not behave differently after R and N. Experiment 2 was similar, except that R_a was milk and R_b food. The same effect of N on experimental animals was obtained. It is argued that the results are relevant to the double-runway ‘frustration effect’, and cannot be explained by existing theories of frustration.     

Motivation concepts and sexual identity

The association dimension of the Picture Identification Test (PIT) was used to investigate the motivation concepts of male and female university students classified as Declared Homosexual, Sexually Uncertain, Clinical Control, and Normal Control. The t test was used to identify Need Association Dyads which discriminated (p < .01) groups. Greater than chance numbers of variables discriminated each of the pairs of groups within each sex except the Sexually Uncertain versus Clinical Control Male groups, the Declared Homosexual versus Clinical Control Female groups, and the Declared Homosexual versus Normal Control Female groups. PIT Need Association Dyads were discussed as a type of implicit personality theory assessment with emphasis on the beliefs subjects hold about the simultaneous expression of needs.