Choice in a variable environment: visit patterns in the dynamics of choice

Molar and molecular views of behavior imply different approaches to data analysis. The molecular view privileges moment-to-moment analyses, whereas the molar view supports analysis of more and less extended activities. In concurrent performance, the molar view supports study of both extended patterns of choice and more local patterns of visiting the choice alternatives. Analysis of the present data illustrated the usefulness of investigating order at various levels of extendedness. Seven different reinforcer ratios were presented within each session, without cues to identify them, and pigeons pecked at two response keys that delivered food on variable-interval schedules. Choice changed rapidly within components as reinforcers were delivered and, following each reinforcer, shifted toward the alternative that produced it. If several reinforcers were delivered consecutively by one alternative, choice favored that alternative, but shifted more slowly with each new reinforcer. A discontinuation of such a series of reinforcers by the delivery of a reinforcer by the other alternative resulted in a large shift of choice toward that alternative. These effects were illuminated by analysis of visits to the two alternatives. Changes in visit length occurred primarily in the first postreinforcer visit to the repeatedly reinforced alternative. All other visits tended to be brief and equal. Performance showed multiple signs of moving in the direction of a fix-and-sample pattern that characterized steady-state performance in earlier experiments with many sessions of maintaining each schedule pair. The analyses of extended and local patterns illustrate the flexibility of a molar view of behavior.     

Effects of drawing on children's item recall

In four experiments, we used item recall tasks to investigate recent claims that young children's event recall can be facilitated by drawing. In Experiments 1 to 3, children of ages 5 to 8 years were tested 4 h after presentation for recall of a set of 25 items that had been presented in groups on a colored, segmented board. In Experiment 1, recall was enhanced by replacement of the objects on the board as they were recalled, but not by drawing them. In Experiments 2 and 3, drawing the board and objects concurrently with or just prior to verbal recall not only failed to facilitate recall, but significantly reduced the number of items reported by 5- to 6-year-olds. In Experiment 4, drawing again impaired recall of items that had been presented as paired associates. Overall, results indicate that under some conditions drawing can impair children's recall rather than facilitate it, as reported in several recent studies.     

Reinforcer-ratio variation and its effects on rate of adaptation

Six pigeons were trained in sessions that consisted of six or seven concurrent-schedule components, each of which could have a different reinforcer ratio arranged in it. The components were unsignaled and occurred in a random order separated by 10-s blackouts. The overall reinforcer rate arranged in each component was 2.22 reinforcers per minute. In Experiment 1, the range of reinforcer ratios in the seven components was varied from a condition in which the ratios were always 1:1, to a condition in which the ratios varied between concurrent variable-interval 27 s extinction (EXT) and concurrent extinction variable-interval 27 s (ratios of 1:EXT, 9:1, 3:1, 1:1, 1:3, 1:9, EXT:1). In Experiment 2, the range of reinforcer ratios was always 27:1 to 1:27, and the presence and absence of the intermediate reinforcer ratios used in Experiment 1 (9:1, 3:1, 1:1, 1:3, 1:9) were investigated. Log response-allocation ratios in components changed rapidly with increasing numbers of reinforcers in components, and Experiment 1 showed that sensitivity to reinforcement was usually higher when the range of reinforcer ratios was greater. When the range of reinforcer ratios was kept constant in Experiment 2, the presence or absence of less extreme reinforcer ratios had no clear effect on sensitivity. At a local level, individual reinforcers had predictable quantitative effects on response ratios: Successive same-alternative reinforcers in a component had rapidly diminishing effects in both experiments. Reinforcers obtained on the opposite alternative to one or more prior reinforcers always had large effects on preference, and these changes were greater when the range of reinforcer ratios was greater. The effects of such reinforcers in changing preference were enhanced, and produced clear preference reversals, when intermediate reinforcer ratios were absent in Experiment 2. Two processes, one local to reinforcers and one with a longer time course, may be necessary to account for these results.     

Concurrent schedules: How responses per reinforcer affects estimates of sensitivity to reinforcement

Conventionally, when choice is measured under concurrent schedules, all responses are included. However, the class of all responses consists of 2 sub-classes which are discriminable by their properties: Reinforced responses always equal obtained reinforcers, while unreinforced responses are free to vary. As a result, the inclusion of reinforced responses in choice measures results in sensitivity values in generalized matching that are biased toward larger values, and this bias becomes extreme in some combinations of overall response and reinforcer rates. Different ways of varying concurrent-schedule values also affect estimated sensitivity and the linearity between choice based on all responses and reinforcer ratios. To avoid spurious results and comparisons, and as a matter of good practice, generalized-matching fits and measures should be done using only unreinforced responses.     

Speculation and theory-building in the development of psychology as a science

In this commentary on a classic article by Paul Wachtel on the importance of theoretical work in empirical research, the author expresses agreement that reward structures discourage the kind of theoretical speculation that may lead to new understandings of existing data and, even more critically, to new ways of formulating questions to be addressed in controlled research. Our students in particular need to be encouraged to reflect on what their own empirical research really means within the larger framework of trying to understand the world in psychological terms. New theories and paradigms do not emerge inevitably from a body of data. Rather, they represent creative insights whose sources are poorly understood and yet are overlooked at our risk.     

A theory of attending, remembering, and reinforcement in delayed matching to sample

A theory of attending and reinforcement in conditional discriminations is extended to working memory in delayed matching to sample by adding terms for disruption of attending during the retention interval. Like its predecessor, the theory assumes that reinforcers and disruptors affect the independent probabilities of attending to sample and comparison stimuli in the same way as the rate of overt free-operant responding as suggested by Nevin and Grace, and that attending is translated into discriminative performance by the model of Davison and Nevin. The theory accounts for the effects of sample-stimulus discriminability and retention-interval disruption on the levels and slopes of forgetting functions, and for the diverse relations between accuracy and sensitivity to reinforcement reported in the literature. It also accounts for the effects of reinforcer probability in multiple schedules on the levels and resistance to change of forgetting functions; for the effects of reinforcer probabilities signaled within delayed-matching trials; and for the effects of reinforcer delay, sample duration, and intertrial-interval duration. The model accounts for some data that have been problematic for previous theories, and makes testably different predictions of the effects of reinforcer probabilities and disruptors on forgetting functions in multiple schedules and signaled trials.     

STIMULUS EFFECTS ON LOCAL PREFERENCE: STIMULUS—RESPONSE CONTINGENCIES,STIMULUS—FOOD PAIRING,AND STIMULUS—FOOD CORRELATION

Four pigeons were trained in a procedure in which concurrent‐schedule food ratios changed unpredictably across seven unsignaled components after 10 food deliveries. Additional green‐key stimulus presentations also occurred on the two alternatives, sometimes in the same ratio as the component food ratio, and sometimes in the inverse ratio. In eight experimental conditions, we varied the contingencies surrounding these additional stimuli: In two conditions, stimulus onset and offset were noncontingent; in another two, stimulus onset was noncontingent, and offset was response contingent. In four conditions, both stimulus onset and offset were contingent, and in two of these conditions the stimulus was simultaneously paired with food delivery. Sensitivity to component food ratios was significantly higher when stimulus onset was response contingent compared to when it was noncontingent. Choice changes following food delivery were similar in all eight conditions. Choice changes following stimuli were smaller than those following food, and directionally were completely determined by the food‐ratio:stimulus‐ratio correlation, not by the stimulus contingency nor by whether the stimulus was paired with food or not. These results support the idea that conditional reinforcers may best be viewed as signals for next‐food location rather than as stimuli that have acquired hedonic value, at least when the signals are differential with respect to future conditions.     

Control by past and present stimuli depends on the discriminated reinforcer differential

The extent to which a stimulus exerts control over behavior depends largely on its informativeness. However, when reinforcers have discriminative properties, they often exert less control over behavior than do other less reliable stimuli such as elapsed time. We investigated why less reliable cues in the present often overshadow stimulus control by more reliable cues presented in the recent past, by manipulating the reliability and duration of stimulus presentations. Five pigeons worked on a modified concurrent schedule in which the location of the response that produced the last reinforcer was a discriminative stimulus for the likely time and location of the next reinforcer. In some conditions, either the location of the previous reinforcer, or the location of the next reinforcer, was signaled by a red key light. This stimulus was either Brief, occurring for 10 s starting a fixed time after the most recent reinforcer, or Extended, being present at all times between food deliveries. Brief and Extended stimuli that signaled the same information had a similar effect on choice when they were present, but control by Brief stimuli weakened as time since stimulus offset elapsed. Control was divided among stimuli in the present and recent past according to the apparent reliability of the information signaled about the next reinforcer. More reliable stimuli in the present degraded, but did not erase, control by less reliable stimuli presented in the recent past. Thus, we conclude that less reliable stimuli in the present control behavior to a greater degree than do more reliable stimuli in the recent past because these more reliable stimuli are forgotten, and hence their relation to the likely availability of food cannot be discriminated.