Key-peck probability and topography in a concurrent variable-interval variable-interval schedule with food and water reinforcers.

The relation between variables that modulate the probability and the topography of key pecks was examined using a concurrent variable-interval variable-interval schedule with food and water reinforcers. Measures of response probability (response rates, time allocation) and topography (peck duration, gape amplitude) were obtained in 5 water- and food-deprived pigeons. Key color signaled reinforcer type. During baseline, response rates and time allocations were greater to the food key than to the water key, and food-key pecks had larger gapes and shorter durations. Relative probability measures (for the food key) were increased by prewatering and decreased by prefeeding. Deprivation effects upon topography measures were apparent only when food- and water-key pecks were analyzed separately. Food-key gape amplitudes increased with prewatering and decreased with prefeeding. The clearest effect occurred with prewatering. There were no consistent effects upon water-key gapes. The key color-reinforcer relation was reversed for 3 pigeons to determine how response topography was modulated during the transition from food- to water-key pecks. Reacquisition was faster for the probability than for the topography measures. Analysis of gape-amplitude distributions during reversal indicated that response-form modulation proceeded through the generation of intermediate gape sizes.     

Time-based and count-based measurement of preference

Rats' pressing on two levers was reinforced according to two independent variable-interval schedules that were varied during the experiment. Since the levers were connected directly to the programming equipment, bypassing the standard pulseformers, reinforcement could occur while a lever was held down. Although the time a lever was pressed might, therefore, have varied independently of number of presses, these two measures covaried substantially, because the average duration of the presses remained roughly constant. This rough invariance may have resulted from the rats' tendency to make bursts of brief presses (i.e., to jiggle the levers), even though the contingencies encouraged holding. When duration did vary, presses on the two levers tended to vary together. As a result, relative time spent pressing corresponded closely to relative number of presses. Both of these measures conformed well to the matching law. Absolute behavioral frequency at a lever, measured either way, varied directly with proportion of reinforcement for that lever, in accordance with the generalized version of the matching law. Number of presses seemed, on balance, to be a slightly more reliable measure than pressing time. The substantial interchangeability may prove more significant than the slight disparity, however, because it supports the notion that all behavior can be measured on a common scale of time.     

Performance in concurrent interval schedules: a systematic replication

Five pigeons were trained on a variety of concurrent interval schedules that arranged reinforcements at either fixed or variable times after the last reinforcement. Two measures were obtained: the number of responses on each schedule, and the time spent responding on each schedule. Ratios of response rates on the two schedules did not equal ratios of reinforcement rates when both schedules were variable nor when one was variable and the other fixed. Ratios of times spent responding approximately equalled ratios of reinforcement rates when both schedules were variable, but did not do so when one was fixed.     

Levels of aggregation: Relative time allocation in concurrent-schedule performance

The proportion of time allocated to one component of a concurrent variable-interval variable-interval schedule was computed for groups of interchangeover times (aggregates) within several intact time series. Variability in obtained proportions decreased as the number of interchangeover times within each aggregate increased; however, modal proportions failed to correspond to overall relative time allocation computed over the course of an entire experimental session, even at the largest aggregate size. The aggregated time series showed periodicities at small aggregate sizes and general trends in local preference at larger aggregate sizes. It is suggested that overall relative time allocation represents a molar extreme in the aggregation of behavior that may not accurately reflect central tendency in the allocation of time to available alternatives within the context of ongoing behavior.     

Sensitivity of time allocation to concurrent-schedule reinforcement

Four pigeons were trained on concurrent variable-interval schedules programmed on a center response key, with access to those schedules controlled by responses on left or right side keys. Two procedures were used. In one, the pigeon was given limited access, in that each side-key response produced 3-s access to a center-key schedule, and in the other procedure, access was unlimited. Data were analyzed using the generalized matching law. Comparison of sensitivities to reinforcement of interchangeover time for both procedures showed them to be of similar magnitude. Response sensitivities were also similar in magnitude for both procedures. From the limited-access procedure a second time measure that was available, switched-in time, was relatively uncontaminated by time spent emitting behavior other than key pecking. Sensitivities to reinforcement for the switched-in time measure were always smaller than interchangeover-time sensitivities for either procedure, and were approximately equal to response sensitivities for the limited-access procedure. Two other access times (5 and 7.5 s) were studied to validate the choice of 3 s as the main access time. These results indicate that when time spent emitting other behavior is excluded from interchangeover time, time and response sensitivities will be approximately equal.     

Undermatching and overmatching as deviations from the matching law

A model of performance under concurrent variable-interval reinforcement schedules that takes as its starting point the hypothetical “burst” structure of operant responding is presented. Undermatching and overmatching are derived from two separate, and opposing, tendencies. The first is a tendency to allocate a certain proportion of response bursts randomly to a response alternative without regard for the rate of reinforcement it provides, others being allocated according to the simple matching law. This produces undermatching. The second is a tendency to prolong response bursts that have a high probability of initiation relative to those for which initiation probability is lower. This process produces overmatching. A model embodying both tendencies predicts (1) that undermatching will be more common than overmatching, (2) that overmatching, when it occurs, will tend to be of limited extent. Both predictions are consistent with available data. The model thus accounts for undermatching and overmatching deviations from the matching law in terms of additional processes added on to behavior allocation obeying the simple matching relation. Such a model thus enables processes that have been hypothesized to underlie matching, such as some type of reinforcement rate or probability optimization, to remain as explanatory mechanisms even though the simple matching law may not generally be obeyed.     

人格维度与注意分配的关系及其选拔意义

本研究以210名男性大学生为被试,EPQ确定人格维度,微机测量注意分配,运用正交设计实验与区组实验相结合的方法综合论述了人格维度与注意分配的关系发现:E、E×N、P×E对注意分配有显著影响,N有一定影响,P和P×N的影响不显著。各影响因素的重要性顺序:E×N→P×E/E→N→P→P×N/误差,绘制了单项人格维度与注意分配关系简图。确定了三种人格维度的最佳组合型(注意分配可望最优):P1N2E1,次佳组合型:P3N2E1,最差组合型:P2N3E1,各型注意分配均值分别为0.702、0.680、0.309,本文探讨了实验结果的选拔意义,认为可从个体EPQ的结果来估测其注意分配能力,这在职业心理选拔中有重要应用价值。     

The allocation of time to temporally defined behaviors: responding during stimulus generalization.

In one stimulus condition, reinforcement depended on rats holding a lever for a duration having both minimum and maximum boundaries. During a second light intensity, reinforcement was not available for some rats; for others, reinforcement depended on a second response duration requirement. Generalization test stimuli controlled the same response durations found during training, and the amount of time allocated to a given response duration depended on the proximity of the test stimulus to the training stimulus which controlled that particular duration. The results indicated that a gradient of stimulus control does not reflect an underlying continuous change in responding, but is a result of the mixing of responses previously controlled by stimuli present during conditioning.     

In Defense of Affirmative Action

Affirmative action refers to positive steps taken to hire persons from groups previously and presently discriminated against. Considerable evidence indicates that this discrimination is intractable and cannot be eliminated by the enforcement of laws. Numerical goals and quotas are justified if and only if they are necessary to overcome the discriminatory effects that could not otherwise be eliminated with reasonable efficiency. Many past as well as present policies are justified in this way.     

Dividing Attention Between Tasks: Testing Whether Explicit Payoff Functions Elicit Optimal Dual‐Task Performance

We test people's ability to optimize performance across two concurrent tasks. Participants performed a number entry task while controlling a randomly moving cursor with a joystick. Participants received explicit feedback on their performance on these tasks in the form of a single combined score. This payoff function was varied between conditions to change the value of one task relative to the other. We found that participants adapted their strategy for interleaving the two tasks, by varying how long they spent on one task before switching to the other, in order to achieve the near maximum payoff available in each condition. In a second experiment, we show that this behavior is learned quickly (within 2–3 min over several discrete trials) and remained stable for as long as the payoff function did not change. The results of this work show that people are adaptive and flexible in how they prioritize and allocate attention in a dual‐task setting. However, it also demonstrates some of the limits regarding people's ability to optimize payoff functions.