人类颜色视觉的计算理论

该文有机地结合了计算视觉理论和生态学视觉理论,指出颜色信息处理的根本任务是检测环境中的光不变量。在此基础上,作者提出了颜色视觉的计算理论以及计算理论本身的生物学标准。初级视觉计算是典型的不适定问题,动物的视觉系统则利用视环境中存在的条件将该不适定问题转化为定解问题。本文引入颜色视觉计算的免要条件,客观性约束,以及颜色认知的神经表象,证明了上述约束下颜色算法的存在性。本文给出了构造颜色知觉的基本假设。同时,该文还讨论了与上述问题密切相关的几个基本问题:神经表象的完备性,主观色觉的客观性,明度知觉和颜色知觉的统一,人类主观色觉的实现方式。     

Utility maximization and melioration: Internalities in individual choice

How do people go about choosing between alternatives in relatively simple settings? This study explores some of the variables that past work suggests may be relevant. Volunteer subjects worked for money in six procedures in which the probability of a payment from either of two alternatives was 1.0, but the rate of pay (i.e. the speed with which a payment was delivered or the size of the payment) interacted with the subjects recent allocation of choices, which we define as the ‘internalities’. Because of the internalities, choosing the currently more profitable alternative did not maximize total earnings. Subjects were more likely to fail to maximize when the interaction between present pay and past choices was spread over longer sequences of choices, or when the reward variable was the speed, rather than the value, of each payment. Subjects often disregarded the internalities and were instead guided by the current yields of the two alternatives, which is a frequently observed tendency, called ‘melioration’, in experiments on choices by animals. The tendency toward melioration was only partially counteracted by explicit instructions on how to maximize earnings. We discuss a theoretical framework for melioration that postulates both motivational and cognitive sources.     

Taking visual disability into account: Explaining failure to experts and non-experts

The present study was designed to investigate visually handicapped students' explanations for failure when the motive to maintain or enhance self-esteem was in conflict with the motive to present a favorable social image. Subjects experienced manipulated failure in a text comprehension task and were subsequently asked to give causal and responsibility attributions in the presence of either a visually handicapped or a non-handicapped experimenter. It was expected that visually disabled participants would claim a handicap-bonus from the non-handicapped experimenter by explicitly presenting non-defensive attributions and accounts as well as handicap-related responses, while defensive explanations should be more pronounced when faced with a blind experimenter. The data provide support for the existence of presumed social expectations as determinants of individuals' verbal self-presentations.     

Family preservation using multisystemic treatment: Long-term follow-up to a clinical trial with serious juvenile offenders

In a randomized clinical trial, multisystemic family preservation was shown to significantly reduce rates of criminal activity and incarceration in a sample of 84 serious juvenile offenders and their multi-need families. In the current study, archival records were searched for re-arrest an average of 2.4 years post-referral. Survival analysis showed that youths who received multisystemic family preservation were less likely to be re-arrested than were youths who had received usual services. Such results represent the first controlled demonstration that family preservation, when delivered via a clearly specified treatment model, has lasting effects with serious juvenile offenders. Implications for family preservation and juvenile justice research are discussed.     

The effects of family composition,family health,parenting behavior and environmental stress on children's divorce adjustment

The traditional family composition model of children's divorce adjustment was compared to a family competence model. Subjects included 81 children whose parents remained married, were divorced, or were divorced and subsequently remarried. Divorced families had been separated for between 24 and 48 months. Custodial parents completed questionnaires regarding family functioning, occurrence of stressful life events, and child's psychosocial adjustment. Children completed questionnaires regarding parenting behaviors and self-esteem. A trained examiner conducted a structured diagnostic interview of the child. Multivariate analysis of covariance showed that family composition had a significant effect on the occurrence of stressful events and change in income but not children's adjustment. Hierarchical multiple regression correlations indicated the most powerful predictors of child adjustment were family competence variables which accounted for 21% of the variance in child adjustment scores. In contrast, family composition accounted for only 8% of variance in child adjustment scores. Further, hierarchical multiple regression correlations indicated that higher levels of family functioning were associated with families where parental hostility was low and parents displayed few rejecting behaviors while practicing consistent and appropriate discipline.     

Delay reduction: current status.

Delay-reduction theory states that the effectiveness of a stimulus as a conditioned reinforcer may be predicted most accurately by the reduction in time to primary reinforcement correlated with its onset. We review support for the theory and then discuss two new types of experiments that assess it. One compares models of choice in situations wherein the less preferred outcome is made more accessible; the other investigates whether frequency of conditioned reinforcement affects choice beyond the effect exerted by frequency of primary reinforcement.     

Momentary maximizing in concurrent schedules with a minimum interchangeover interval

Eight pigeons were trained on concurrent variable-interval variable-interval schedules with a minimum interchangeover time programmed as a consequence of changeovers. In Experiment 1 the reinforcement schedules remained constant while the minimum interchangeover time varied from 0 to 200 s. Relative response rates and relative time deviated from relative reinforcement rates toward indifference with long minimum interchangeover times. In Experiment 2 different reinforcement ratios were scheduled in successive experimental conditions with the minimum interchangeover time constant at 0, 2, 10, or 120 s. The exponent of the generalized matching equation was close to 1.0 when the minimum interchangeover time was 0 s (the typical procedure for concurrent schedules without a changeover delay) and decreased as that duration was increased. The data support the momentary maximizing theory and contradict molar maximizing theories and the melioration theory.     

The asymptotic posterior normality of the latent trait in an IRT model

It has long been part of the item response theory (IRT) folklore that under the usual empirical Bayes unidimensional IRT modeling approach, the posterior distribution of examinee ability given test response is approximately normal for a long test. Under very general and nonrestrictive nonparametric assumptions, we make this claim rigorous for a broad class of latent models.This research was partially supported by Office of Naval Research Cognitive and Neural Sciences Grant N0014-J-90-1940, 442-1548, National Science Foundation Mathematics Grant NSF-DMS-91-01436, and the National Center for Supercomputing Applications. We wish to thank Kumar Joag-dev and Zhiliang Ying for enlightening suggestions concerning the proof of the basic result.The authors wish to thank Kumar Joag-Dev, Brian Junker, Bert Green, Paul Holland, Robert Mislevy, and especially Zhiliang Ying for their useful comments and discussions.