Time of day and the representation of text

This article reports an experiment to investigate the idea that time-of-day differences in memory for text are related to type of text processing that is carried out at different times of day. In particular, it was hypothesized that subjects tested in the morning tend to retain more of the exact wording of the text, whereas those tested in the afternoon are more likely to produce a meaning-based representation. The results of a recognition test showed that, in agreement with other studies, immediate text memory is better in the morning than in the afternoon. As predicted, the subjects tested in the morning better remembered the exact wording of the original passages. However, the idea that memory for meaning is better in the afternoon than the morning was not supported by the data. The results suggest that subjects at both times of day produce a meaning-based representation of the text but, in the morning, this representation is supported by good verbatim memory, enabling accurate recall of the text at that time.     

The societal and psycho-sociological background of football hooliganism

On October 11, 1985, the Belgian Council of Ministers ordered scientific research on violence on the football terraces. This research was conducted in the years 1986 and 1987 by the “Onderzoeksgroep Jeugdcriminologie” (Research group on Juvenile Criminology) of the K.U. Leuven in close relationship with the general police of the home office. (The report was submitted on December 23, 1987 [VAN LIMBERGEN, COLAERS en WALGRAVE, 1987].)     

Some comments on the projectibility of anthropological hypotheses: Samoa briefly revisited

The purpose of this article is to examine the applicability of the theory of projection for Anthropological hypotheses. The claim is made that Goodman's classic statement of the problem does not apply in its entirety to actual Anthropological hypotheses. The recent Freeman-Mead debate is employed as a framework for the discussion, illustrating that the issue of projectibility, while central for the social sciences, is best used as a backdrop to illustrate several important methodological problems. For Anthropology, and other related social sciences, the central methodological problem, which is directly related to the projectibility one, is the development and justification of evidence-rules that can be used for a theory of confirmation. A preliminary attempt is then made to articulate the nature of these rules within the general Hempelian framework of qualitative confirmation.     

Choice in situations of time-based diminishing returns: immediate versus delayed consequences of action.

Pigeons chose between two schedules of food presentation, a fixed-interval schedule and a progressive-interval schedule that began at 0 s and increased by 20 s with each food delivery provided by that schedule. Choosing one schedule disabled the alternate schedule and stimuli until the requirements of the chosen schedule were satisfied, at which point both schedules were again made available. Fixed-interval duration remained constant within individual sessions but varied across conditions. Under reset conditions, completing the fixed-interval schedule not only produced food but also reset the progressive interval to its minimum. Blocks of sessions under the reset procedure were interspersed with sessions under a no-reset procedure, in which the progressive schedule value increased independent of fixed-interval choices. Median points of switching from the progressive to the fixed schedule varied systematically with fixed-interval value, and were consistently lower during reset than during no-reset conditions. Under the latter, each subject's choices of the progressive-interval schedule persisted beyond the point at which its requirements equaled those of the fixed-interval schedule at all but the highest fixed-interval value. Under the reset procedure, switching occurred at or prior to that equality point. These results qualitatively confirm molar analyses of schedule preference and some versions of optimality theory, but they are more adequately characterized by a model of schedule preference based on the cumulated values of multiple reinforcers, weighted in inverse proportion to the delay between the choice and each successive reinforcer.     

Stimulus control of behavioral history.

Pigeons were exposed to two different reinforcement schedules under different stimulus conditions in each of two daily sessions separated by 6 hr (Experiments 1 and 2) or in a single session (Experiment 3). Following this, either a fixed-interval (Experiment 1) or a variable-interval schedule (Experiments 2 and 3) was effected in both stimulus conditions. In the first two experiments, exposure to fixed-ratio or differential-reinforcement-of-low-rate schedules led to response-rate, but not pattern, differences in subsequent performance on fixed- or variable-interval schedules that persisted for up to 60 sessions. The effects of reinforcement-schedule history on fixed-interval schedule performance generally were more persistent. In Experiment 3, a history of high and low response rates in different components of a multiple schedule resulted in subsequent response-rate differences under identical variable-interval schedules. Higher response rates initially occurred in the component previously correlated with high response rates. For 3 of 4 subjects, the differences persisted for 20 or more sessions. Previous demonstrations of behavioral history effects have been confined largely to between-subject comparisons. By contrast, the present results demonstrate strong behavioral effects of schedule histories under stimulus control within individual subjects.     

Low-dose caffeine discrimination and self-reported mood effects in normal volunteers.

A caffeine versus placebo discrimination procedure was used to determine the lowest caffeine dose that could produce discrimination and self-reported mood effects in normal volunteers. During daily sessions under double-blind conditions, caffeine-abstinent subjects orally ingested a capsule containing 178 mg caffeine or placebo. Before beginning discrimination training, the compounds were identified to subjects by letter codes. Fifteen, 30, and 45 min after capsule ingestion, subjects guessed the capsule's letter code. Correct guesses at 45 min earned money. After each session, subjects received a supplementary capsule containing caffeine or placebo to ensure that, within each phase of the study, subjects received the same daily dose of caffeine equal to the training dose. Five of the 15 subjects acquired the caffeine versus placebo discrimination within the first 20 sessions (greater than or equal to 75% correct); 6 other subjects acquired the discrimination with additional training. Nine subjects who acquired the discrimination were subsequently trained at progressively lower caffeine doses. In general, the lowest dose to produce discrimination (greater than or equal to 75% correct) was also the lowest dose to produce self-reported mood effects: 4 subjects showed discrimination and self-reported mood effects at 100 mg caffeine, 2 at 56 mg, 1 at 32 mg, and 1 at 18 mg. One of these subjects also showed self-reported mood effects at 10 mg. The present study documents discriminative stimulus and self-reported mood effects of caffeine at doses below those previously shown to affect any behavior in normal volunteers.     

The nonequivalence of behavioral and mathematical equivalence.

Sidman and his colleagues derived behavioral tests for stimulus equivalence from the axiom in logic and mathematics that defines a relation of equivalence. The analogy has generated abundant research in which match-to-sample methods have been used almost exclusively to study interesting and complex stimulus control phenomena. It has also stimulated considerable discussion regarding interpretation of the analogy and speculation as to its validity and generality. This article reexamines the Sidman stimulus equivalence analogy in the context of a broader consideration of the mathematical axiom than was included in the original presentation of the analogy and some of the data that have accumulated in the interim. We propose that (a) mathematical and behavioral examples of equivalence relations differ substantially, (b) terminology is being used in ways that can lead to erroneous conclusions about the nature of the stimulus control that develops in stimulus equivalence experiments, and (c) complete analyses of equivalence and other types of stimulus-stimulus relations require more than a simple invocation of the analogy. Implications of our analysis for resolving current issues and prompting new research are discussed.     

Behavioral contrast: Pavlovian effects and anticipatory contrast.

Two sources of behavioral contrast have been identified previously: Pavlovian stimulus-reinforcer relations and component sequence effects (anticipatory contrast). This study sought to isolate these sources of control procedurally in a four-ply multiple schedule composed of two fixed two-component sequences. Different cues were associated with the first component of each sequence, and contrast effects were studied in these target components. In Experiment 1, differential cuing of Component 2 between sequences and availability of reinforcement during target components were varied across three groups of pigeons; the stimulus-reinforcer relation between target-component cues and schedule of reinforcement in Component 2 was varied within subjects. Control by the Pavlovian relation was demonstrated under all conditions, and anticipatory contrast was not observed. In Experiment 2, target-component duration was systematically varied in the three groups of Experiment 1. Control by the Pavlovian relation was reliably obtained only when target-component behavior was unreinforced, and diminished with increases in component duration. Anticipatory contrast emerged in the two groups for which target-component reinforcement was available. These and other data indicate that Pavlovian effects in multiple schedules may be obscured when the requisite conditions for anticipatory contrast are present.     

Comparison of variance and covariance patterns in parallel and serial theories of timing.

Parallel and serial timing processes are analyzed for their account of the dynamics of intertrial responding in the peak procedure. A strictly serial model, such as the behavioral theory of timing (Killeen & Fetterman, 1988), does not fit the dynamic correlation pattern in the location and duration of the middle high-rate responding portion of peak trials. In contrast, the parallel scalar expectancy theory model, with a sample for memory and threshold, does fit this pattern. A modification of the serial model is presented that also accommodates the within-trial covariance pattern. The modification, which is formally equivalent to a model for human tapping (Wing & Kristofferson, 1973), entails the addition of concurrent processes operating in parallel with serial timing.