Response-cost punishment with pigeons: Further evidence of response suppression via token loss

Four pigeons responded on a two-component multiple token-reinforcement schedule, in which tokens were produced according to a random-interval 30-sec schedule and exchanged according to a variable-ratio 4 schedule in both components. To assess the effects of contingent token loss, tokens were removed after every second response (i.e., fixed-ratio 2 loss) in one of the components. Response rates were selectively lower in the loss components relative to baseline (no-loss) conditions, as well as to the within-condition no-loss components. Response rates were decreased to a greater degree in the presence of tokens than in their absence. To control for the effects of changes in the density of token and food reinforcement, two parts consisted of additional conditions where food density and token loss were yoked to those in a previous loss condition. In the yoked-food condition, tokens were produced as usual in both components, but the overall density of food reinforcement in one of the components was yoked to that obtained during a previous token-loss condition. In the yoked token-loss condition, tokens were removed during one component of the multiple schedule at a rate that approximately matched the obtained rate of loss from a previous token-loss condition. Response rates in these yoked components were less affected than those in comparable loss components, despite similar densities of token, exchange, and food reinforcement. On the whole, the results support the conclusion that contingent token loss serves as an effective punisher with pigeons.     

Children's internal organization of locative categories

4 locative categories were investigated to determine whether their examples were organized according to the prototype/nonprototype distinction. A ranking task was presented to 30 adult subjects to see whether they would judge those instances which had been designated as prototypes by the experimenter to be the best exemplars of each category. An elicited-drawing task was administered to see whether there was a preference for drawing adult-designated prototypical instances. A matching task was presented to determine whether fewer errors would occur in response to adult-designated prototypical instances. The latter 2 tasks were presented to 4-year-olds, 6-year-olds, and adults, with 17 subjects in each group. The results provide strong evidence of prototype/nonprototype organization in 3 of the locative categories and weak evidence in the fourth. Tentative conclusions regarding the development of such organization are drawn.     

Exploring the Effects of Financial Aid on the Gap in Student Dropout Risks by Income Level

Using national survey data and discrete-time logit modeling, this research seeks to understand whether student aid mediates the relationship between parental income and student dropout behavior. Our analysis confirms that there is a gap in dropout rates for low-income students compared with their upper income peers, and suggests that some types of aid are associated with lower risks of dropout. Thus, we examine the interaction between financial aid type and parental income to explore whether, and if so how, different types of aid may reduce the dropout gap by income level group. We find that the receipt of a Pell grant is related to narrowing the dropout gap between students from low- and middle-income groups, although overall the interaction between Pell grant and income is not significant. Loans and work-study aid both have similar effects on student dropout across all income groups. Methodologically, our results demonstrate the need to model dropout behavior temporally and to avoid main-effect bias by incorporating interaction effects.

Improving the compositions of students with learning disabilities using a strategy involving product and process goal setting.

This study was conducted to determine if a planning and writing strategy would improve the essay writing of students with learning disabilities. Four participants were taught a strategy designed to facilitate the setting of product and process goals, generation and organization of notes, continued planning during writing, and evaluation of goal attainment. Training effects were investigated using a multiple probe design across subjects. Strategy instruction had a positive effect on students' essay writing performance and knowledge of the writing process, and effects were maintained over time.     

The Effect of Relationship on Children's Distributive Justice Reasoning

Kindergarten, third-grade, and sixth-grade children were told 2 stories about a group of children who made artwork that was subsequently sold at a craft fair. The characters in one story were described as friends, while the characters in the other story were described as strangers (relationship condition). 1 character in each story was presented as the oldest in the group, 1 as the most productive, and 1 as the poorest. Children were asked to allocate 9 dollars to the 3 characters under each relationship condition, provide rationales for those allocations, and rate the fairness of 4 different patterns of allocation. Older children allocated more money to needy friends than to needy strangers and more to productive strangers than to productive friends. Kindergartners' allocations and fairness ratings did not vary with relationship. Rationales for allocation judgements suggested that equality was the most salient principle for decisions at all ages, but the older children provided rationales based on benevolence more often than younger children when characters were presented as friends.     

Noise assisted directed motion at the molecular level — 2

The term noise is used to describe fluctuations about the mean deterministic stationary value of a physical quantity. It is now being increasingly realised that noise is an important ingredient to bring order in dynamical processes. Though it appears counterintuitive, noise seems to help in directing transport processes in biological systems at the molecular level. In Part 2 of the article, we discuss some more examples of noise assisted directed motion.