PREFERENCE REVERSALS DUE TO MYOPIC DISCOUNTING OF DELAYED REWARD

Abstract— A basic stationarity axiom of economic theory assumes stable preference between two deferred goods separated by a fixed time. To test this assumption, we offered subjects choices between delayed rewards, while manipulating the delays to those rewards. Preferences typically reversed with changes in delay, as predicted by hyperbolic discounting models of impulsiveness. Of 36 subjects, 34 reversed preference from a larger, later reward to a smaller, earlier reward as the delays to both rewards decreased. We conclude that the stationarity axiom is not appropriate in models of human choice.     

ADULTS LISTEN SELECTIVELY; INFANTS DO NOT

Abstract— Infants' auditory detection thresholds are higher than adult thresh olds. Since adults listen selectively for an expected test tone frequency, and selective listening improves their detection performance, one hypothesis about why infant thresholds are high is that infants do not listen selectively. This hypothesis was tested by obtaining listening bands from adults and from 7- to 9-month-old infants. The results replicate earlier findings that adults listen selectively but indicate that infants do not. Lack of selective listening likely contributes to infants' high thresholds. Further, the finding that infants and adults have different listening strategies has implications for infants' auditory perception in general.     

Abuse and neglect of adults with mental retardation in different residential settings

Eighty-two per cent of all cases of abuse or neglect of an adult with mental retardation substantiated by the Abuse Investigation Division of the Connecticut Office of Protection and Advocacy for Persons with Disabilities over a five-year period occurred in the victim's residence. Chi square analyses revealed that there was significantly more abuse in institutions and group homes and significantly less in the individual's own home. Furthermore, analyses revealed that there was significantly more personal neglect in group homes and community training homes and significantly less in own homes. The results were discussed and recommendations made regarding ways of reducing abuse and neglect.     

Compound word effects differ in reading,on-line naming,and delayed naming tasks

Bimorphemic compound words (e.g.,blueberry), bimorphemic suffixed words (e.g.,ceaseless), and monomorphemic controls (e.g.,arthritis) were read in neutral sentence contexts in Experiment 1. The main result revealed longer first fixation durations on compound words than on control and suffixed words. Different effects emerged when naming tasks were used. An on-line naming task revealed substantially shorter naming latencies for compound words than for control and suffixed words. Naming latencies for compound and control words were equivalent in a delayed naming task. These results indicate that on-line naming latencies and word-viewing durations may yield diverging results. They also suggest that activation of constituent words of compound words occurs independently from the specification of conventional word meanings.     

Delay-discounting probabilistic rewards: Rates decrease as amounts increase

The independence of delay-discounting rate and monetary reward size was tested by offering subjects (N = 621) a series of choices between immediate rewards and larger, delayed rewards. In contrast to previous studies, in which hypothetical rewards have typically been employed, subjects in the present study were entered into a lottery in which they had a chance of actually receiving one of their choices. The delayed rewards were grouped into small ($30–$35), medium ($55–$65), and large amounts ($70–$85). Using a novel parameter estimation procedure, we estimated discounting rates for all three reward sizes for each subject on the basis of his/her pattern of choices. The data indicated that the discounting rate is a decreasing function of the size of the delayed reward (p < .0001), whether hyperbolic or exponential discounting functions are assumed. In addition, a reliable gender difference was found (p = .005), with males discounting at higher rates than females, on average.     

The interactive effect of introversion-extraversion with caffeine induced arousal on verbal performance

In a test of the arousal hypothesis of introversion-extraversion, subjects were pre- and post-tested on practice Graduate Record Examination verbal performance items while administered caffeine at either 0, 2, or 4 mg/kg of body weight. Introverts increased dramatically in performance between the 0 and 2 mg/kg conditions and then decreased even more dramatically between the 2 and 4 mg/kg conditions. Extraverts showed decrements in performance at the 0 mg/kg level, improved slightly at the 2 mg/kg level, and showed marked improvement at the 4 mg/kg level. Further analyses revealed that introverts increased in both speed and accuracy at low levels of stimulation but then decreased in both at higher levels of stimulation. Extraverts showed continued increases in speed and accuracy across the increasing arousal levels.     

THE DEVELOPMENT OF KNOWLEDGE CONCERNING WRITTEN ARITHMETIC: A CROSS-CULTURAL STUDY

This study is concerned with the manner in which Western mathematics is assimilated by children raised in traditional African cultures. It was predicted that after an initial period of difficulty in learning school arithmetic, African children (Baoulé and Dioula from the Ivory Coast) acquire basic concepts, develop invented strategies, and make errors similar to those of American children. Further, it was predicted that Dioula children, since they are members of a commercial culture, perform at a somewhat higher level than the Baoulé, members of a farming culture which does not seem to stress computational activity. To investigate these hypotheses, American, Baoulé, and Dioula children at two age levels were given a variety of arithmetic problems involving basic skills (e.g., reading numbers), number knowledge (e.g., place value), and calculational abilities (e.g., written computation). The results showed that, in general, older African and American children (fifth- and sixth-graders) were quite similar in all respects. The only large and significant differences occurred in the case of younger children (second- and third-graders). At this level American children generally performed at a higher level than Africans, as predicted, and Dioula occasionally at a higher level than Baoulé, also as predicted. At the same time, qualitative aspects of African and American children's performance were similar: for example, both groups made the same types and proportions of errors in written calculations. The results generally support the hypotheses and can be explained in terms of both educational and cognitive factors.