Pigeons' choices in situations of diminishing returns: fixed- versus progressive-ratio schedules.

In two different discrete-trial procedures, pigeons were faced with choices between fixed-ratio and progressive-ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive-ratio schedule that increased in increments of 20 throughout a session and a fixed-ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed-ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive-ratio schedule back to its minimal value. In the no-reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed-ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline & Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums-of-reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no-reset conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

REPLICATION OF THE ACHIEVEMENT PLACE MODEL IN CALIFORNIA1

Attempting to replicate procedures from Achievement Place, token reinforcement procedures were used to modify savings, conversational interruptions, and table-setting of delinquent boys residing in a home-style, community based, treatment setting. The tokens (points) were redeemable for various privileges and could be earned for specified appropriate behaviors and lost for specified inappropriate behaviors. Contingent point fines reduced the frequency of interruptions. Point rewards improved table-setting, but even large point rewards did not substantially increase savings. Baseline data indicated that lateness to dinner was not a problem, as it was in Achievement Place. Withdrawal of contingent points and back-up rewards did not disrupt the clean-up behavior of two boys.     

Control of the temporal locations of polydipsic licking in the rat.

We studied the variables controlling the temporal location of polydipsic licking. Four rats were trained on a mixed fixed-ratio 10 (no tone) chained fixed-ratio 10 (no tone) fixed-ratio 90 (tone) schedule and on a multiple fixed-ratio 10 (tone) fixed ratio 100 (no tone) schedule. On the multiple schedule, drinking followed pellets if a fixed ratio 100 was upcoming for all four subjects and for two of the subjects if a fixed ratio 10 was upcoming. On the mixed schedule, drinking preceded the fixed-ratio 90 component of the chain. Two subjects also drank after pellet delivery on the mixed schedule before both the fixed ration 10 and the chain components. The number of licks was greater following a pellet than following a response. In a second phase with two of these subjects, the total response requirement of the chain was held constant at 100, while the size of the two ratios that constituted the chain was varied inversely. The tone signaled onset of the second link. Drinking followed the tone when it signaled fixed-ratio 90, 95, or 100 but not when it signaled fixed ratio 75, 80, or 85. These results show, on the one hand, that polydipsic licking is controlled by discriminative properties of the pellet rather than by its eliciting or "thirst-producing" characteristics. On the other hand, the fact that drinks were longer following a pellet than following a response suggests a contribution of thirst to polydipsia.     

Species differences in temporal control of behavior II: human performance

Human subjects responded on two panels. A differential-reinforcement-of-low-rate schedule with a limited-hold contingency operated on Panel A. In Condition 1, responses on Panel B produced a stimulus on the panel that signalled whether reinforcement was available on Panel A. In Condition 2, responses on Panel B briefly illuminated a digital clock. In both conditions, performance on Panel A was very efficient; with few exceptions, Panel A was pressed only when reinforcement was available. Thus, in effect, a fixed-interval schedule operated on Panel B. In Condition 1, a “break-and-run” response pattern occurred on Panel B; with increasing temporal parameters, the duration of the postreinforcement pause on Panel B increased linearly while overall response rate and running rate (calculated by excluding the postreinforcement pauses) remained approximately constant. In Condition 2, the response pattern on Panel B was scalloped; the postreinforcement pause was a negatively accelerated increasing function of schedule value, while overall response rate and running rate were negatively accelerated decreasing functions of schedule value. The performance of subjects in Condition 2, but not in Condition 1, was highly sensitive to the contingencies in operation, and resembled that of other species on the fixed-interval schedule.     

(Not) giving credit where credit is due: Citation of data sets

Adequate Citation of data sets is crucial to the encouragement of data sharing, to the integrity and cost-effectiveness of science and to easy access to the work of others. The citation behavior of social scientists who have published based on shared data was examined and found to be inconsistent with important ideals of science. Insights gained from the social sciences, where data sharing is somewhat customary, suggest policies and incentives that would foster adequate citation by secondary users, and greater openness and sharing in other disciplines.     

Finite Sets and Natural Numbers in Intuitionistic TT Without Extensionality

In this paper, we prove that Heyting's arithmetic can be interpreted in an intuitionistic version of Russell's Simple Theory of Types without extensionality.     

Euclidean Hierarchy in Modal Logic

For a Euclidean space , let L _n denote the modal logic of chequered subsets of . For every n 1, we characterize L _n using the more familiar Kripke semantics, thus implying that each L _n is a tabular logic over the well-known modal system Grz of Grzegorczyk. We show that the logics L _n form a decreasing chain converging to the logic L of chequered subsets of . As a result, we obtain that L is also a logic over Grz, and that L has the finite model property. We conclude the paper by extending our results to the modal language enriched with the universal modality.     

Unconscious activation of task sets

Using an explicit task cuing paradigm, we tested whether masked cues can trigger task-set activation, which would suggest that unconsciously presented stimuli can impact cognitive control processes. Based on a critical assessment of previous findings on the priming of task-set activation, we present two experiments with a new method to approach this subject. Instead of using a prime, we varied the visibility of the cue. These cues either directly signaled particular tasks in Experiment 1, or certain task transitions (i.e., task repetitions or switches) in Experiment 2. While both masked task and transition cues affected task choice, only task cues affected the speed of task performance. This observation suggests that task-specific stimulus–response rules can be activated only by masked cues that are uniquely associated with a particular task. Taken together, these results demonstrate that unconsciously presented stimuli have the power to activate corresponding task sets.