Changes in functional response units with briefly delayed reinforcement

In two experiments, key-peck responding of pigeons was compared under variable-interval schedules that arranged immediate reinforcement and ones that arranged unsignaled delays of reinforcement. Responses during the nominal unsignaled delay periods had no effect on the reinforcer presentations. In Experiment 1, the unsignaled delays were studied using variable-interval schedules as baselines. Relative to the immediate reinforcement condition, 0.5-s unsignaled delays decreased the duration of the reinforced interresponse times and increased the overall frequency of short (<0.5-s) interresponse times. Longer, 5.0-s unsignaled delays increased the duration of the reinforced interresponse times and decreased the overall frequency of the short interresponse times. In Experiment 2, similar effects to those of Experiment 1 were obtained when the 0.5-s unsignaled delays were imposed upon a baseline schedule that explicitly arranged reinforcement of short interresponse times and therefore already generated a large number of short interresponse times. The results support earlier suggestions that the unsignaled 0.5-s delays change the functional response unit from a single key peck to a multiple key-peck unit. These findings are discussed in terms of the mechanisms by which contingencies control response structure in the absence of specific structural requirements.     

ON MARTIN EGER'S "A TALE OF TWO CONTROVERSIES"

Abstract. Criticisms are presented against Eger's challenge to the demarcation between the natural sciences and ethics. Arguments are given both against his endorsement of the "new" philosophy of science and against his rejection of the fact-value dichotomy. However, his educational recommendations are reinforced rather than weakened by these criticisms     

个人化设计在临床研究中的应用——从个体角度研究个体差异

本文从有关研究证据的基础上,介绍了个人化设计的理论基础和实验设计,并在此基础上讨论了个人化设计在临床研究领域中的应用价值,总结出一种适合临床病人使用的研究程序。个人化设计允许对个体的个人价值进行分析,并能同时研究不同刺激信息的作用,在个体水平上分析个体差异。通过简化了的实验程序,个人化设计为解决临床研究中的问题提供了一种新的思维方式。文中还对相关研究法的局限进行了讨论。     

Theory change in immunology part II: The clonal selection theory

This two-part article examines the competition between the clonal selection theory and the instructive theory of the immune response from 1957–1967. In Part I the concept of a temporally extended theory is introduced, which requires attention to the hitherto largely ignored issue of theory individuation. Factors which influence the acceptability of such an extended theory at different temporal points are also embedded in a Bayesian framework, which is shown to provide a rational account of belief change in science. In Part II these factors, as elaborated in the Bayesian framework, are applied to the case of the success of the clonal selection theory and the failure of the instructive theory.     

Least-squares approximation of an improper correlation matrix by a proper one

An algorithm is presented for the best least-squares fitting correlation matrix approximating a given missing value or improper correlation matrix. The proposed algorithm is based upon a solution for Mosier's oblique Procrustes rotation problem offered by ten Berge and Nevels. A necessary and sufficient condition is given for a solution to yield the unique global minimum of the least-squares function. Empirical verification of the condition indicates that the occurrence of non-optimal solutions with the proposed algorithm is very unlikely. A possible drawback of the optimal solution is that it is a singular matrix of necessity. In cases where singularity is undesirable, one may impose the additional nonsingularity constraint that the smallest eigenvalue of the solution be , where is an arbitrary small positive constant. Finally, it may be desirable to weight the squared errors of estimation differentially. A generalized solution is derived which satisfies the additional nonsingularity constraint and also allows for weighting. The generalized solution can readily be obtained from the standard unweighted singular solution by transforming the observed improper correlation matrix in a suitable way.     

The psychophysics of spending

Several theories of decision making are based, in part, upon the principles of psychophysics (Kahneman and Tversky, 1979; Thaler, 1985). For example, due to the psychophysics of quantity, the difference between $10 and $20 seems greater than the difference between $110 and $120. To determine whether psychophysics influences consumers' decisions, subjects in four studies made real or hypothetical purchases. It was predicted that as the size of the purchase increased, subjects would be more willing to buy additional smaller items. Small extra purchases should seem like minor expenditures when they follow larger purchases. Results of the four studies supported our hypothesis. In addition, it was found that subjects responded not only to actual changes in purchase size but also to changes in the presentation or framing of a purchase.     

A nonparametric approach for assessing latent trait unidimensionality

Assuming a nonparametric family of item response theory models, a theory-based procedure for testing the hypothesis of unidimensionality of the latent space is proposed. The asymptotic distribution of the test statistic is derived assuming unidimensionality, thereby establishing an asymptotically valid statistical test of the unidimensionality of the latent trait. Based upon a new notion of dimensionality, the test is shown to have asymptotic power 1. A 6300 trial Monte Carlo study using published item parameter estimates of widely used standardized tests indicates conservative adherence to the nominal level of significance and statistical power averaging 81 out of 100 rejections for examinee sample sizes and psychological test lengths often incurred in practice.The referees' comments were remarkably detailed and greatly enhanced the writeup and sensitized the author to certain pertinent issues. Discussions with Fritz Drasgow, Lloyd Humphreys, Dennis Jennings, Brian Junker, Robert Linn, Ratna Nandakumar, and Robin Shealy were also very useful.This research was supported by the Office of Naval Research under grant N00014-84-K-0186; NR 150-533, and by the National Science Foundation under grant DMS 85-03321.     

Political Extremism and a Generalized Propensity to Discriminate Among Values

Research exploring the psychological differences between people supporting extreme versus moderate ideologies is growing. However, this research has rarely examined the domain of values. Here, we explore this domain by assessing the possibility that political extremists discriminate more among values compared to moderates, namely, that extremists exhibit strong commitment toward some values at the expense of other values, whereas moderates would acknowledge a multiplicity of values as equally important. First, we propose a model positing that a value discriminability parameter captures a general tendency to discriminate among values. Second, we test empirically the prediction that, compared to moderates, political extremists exhibit a higher discriminability parameter. This prediction is supported by four studies (including one based on the European Social Survey where representative samples from 29 European countries are examined) where participants reported their ideological orientation and rated the importance of basic human values (we focused on basic values because these transcend the political domain, thus highlighting general effects). Specifically, in all studies we observed a positive correlation between political extremism and residual variability in ratings, a hallmark of a higher discriminability parameter. These findings highlight the value domain as critical to understanding differences between political extremists and moderates.     

La balance optimisme/pessimisme : détermination des styles d’expectations envers le futur en se basant sur la bidimensionnalité du Life Orientation Test–Revised

IntroductionSince the 1980s, two major conceptions of the representation of optimism and pessimism have been disputed: a unidimensional structure and a bidimensional structure.ObjectiveThe bidimensional properties of the LOT-R in French are further explored in order to determine the styles of expectations towards the future according to the levels of optimism and pessimism.MethodA study carried out on a sample of 913 adults from France (72.7% women, M = 41.14 years) proposes (1) to analyze the factorial structure of the instrument, the relationship between the two constructs as well as their separability, (2) to explore the styles of expectations according to the levels of positive and negative expectations by latent profile analysis, (3) to study the influence of socio-demographic factors (age, sex, socio-professional category) on cognitive expectations about the future.ResultsThe confirmatory factor analyzes establish the replicability of the bidimensional latent structure of the instrument across age and gender groups, with the separability between the two constructs increasing with advancing age. The latent profile analysis supports the existence of three styles of expectations towards the future within the sample: the optimistic style, the mixed style and the pessimistic style. The MIMIC model demonstrates that increasing age and socio-professional category are determinants of levels of optimism and pessimism as well as of expectation styles.ConclusionThis research makes it possible to use the styles of expectations towards the future which empirically models the balance between the levels of optimism and pessimism.