Johan Hueting

Expectancy or automatic facilitation? Separating sequential effects in two-choice reaction time.

Two concepts have been proposed to explain sequential effects in serial reaction time, namely, automatic facilitation and subjective expectancy. The present study clarifies the relation between these concepts and specific data patterns obtained in a two-choice task. The proposed repetition-alternation function is particularly suited to distinguish the benefit-only pattern of automatic facilitation from the cost-benefit pattern of expectancy in higher order sequential effects. The data indicate that facilitation and expectancy are independent mechanisms that react in a different way to manipulations of response-stimulus interval, compatibility, and practice. It is suggested that facilitation effects are decaying memory traces related to the structural pathway of the reaction process, whereas expectancy effects are functional and only intervening in the information flow when enough time is available.

Effect of amphetamine on long-term retention of verbal material

A series of five experiments was conducted to investigate the temporal aspects of human memory consolidation of symbolic material through the administration of amphetamine. Subjects had to recall or recognise unrelated words from a previously presented list. The first experiments support the conjecture, based on animal studies, that amphetamine enhances long-term memory performance. Subsequently, enhancement is demonstrated with oral administration before learning, as well as with intramuscular injection after learning. It is shown that improved recall cannot be explained solely by general arousal or attentional processes, but must be due to consolidation. By introducing different test delays we show that consolidation of symbolic material can be modulated by amphetamine during the 1st hour after learning. In a final experiment we demonstrate that the memory enhancement applies to recall as well as to recognition. The implications of the present results are discussed in the context of recent research on LTP processes.

Amphetamine enhances human-memory consolidation

Although it is generally accepted that CNS stimulants have enhancing effects on long-term storage processes in laboratory animals, little is known about their influence on human learning. We report a series of experiments with free recall of lists of unrelated words, demonstrating a significant enhancement on long-term retention after amphetamine administration. A gradual increase of recall was observed up to 1 h after learning, remaining stable for at least 3 days, after oral administration before learning as well as intramuscular injection after learning. The results show that research on humans with drug-induced memory-enhancement techniques is necessary to supplement the animal studies for the understanding of the mechanisms involved in information consolidation.

Automatic aftereffects in two-choice reaction time: a mathematical representation of some concepts.

A mathematical model is developed to describe sequential effects in two-choice reaction time experiments with a short response-stimulus interval. Evidence is briefly discussed that in conditions with short response-stimulus intervals, automatic aftereffects dominate sequential effects, and the influence of subjective expectancy can be neglected. In these conditions the model premises three components of automatic aftereffects--facilitation, inhibition, and noise, with a common decay factor. Influence of response-stimulus interval and practice on sequential effects are examined and related to parameter changes in the proposed single-decay model. The decrease of automatic aftereffects with increasing response-stimulus interval is primarily ascribed to an increasing decay factor. The parameter representation of the model also clarifies the issue of the disappearance of automatic aftereffects with practice. It shows a gradual fading of inhibition in the initial stages of practice, together with a slower decrease of the facilitation effect. The single-decay model provides a satisfactory explanation for the processes involved in compatible two-choice reaction time with short response-stimulus interval.

Traces of fatigue in an attention task

The present study is one in a series undertaken to analyze the influence of physical fatigue on a visual perception task. Thirty minutes after being exhausted on a bicycle ergometer, 20 subjects executed a visual perception task involving tachistoscopically presented random groups of 3 to 12 dots. The subjects responded by reporting the number of dots, and their response times were measured. Under the influence of fatigue, the number of correct responses decreased, especially for the larger groups of dots. No significant differences in response times were found between fatigued and nonfatigued subjects. We conclude that fatigued subjects avoid attention that demands controlled processing and tend to adhere to uniform automatic processing.

Traces of fatigue in an attention dual task

Effects of physical effort have been difficult to find in attention tasks for various reasons, such as the activating effect of the laboratory situation or the spare capacity in automated tasks. Instead, a double task, reflecting quantitatively the changes of information processing, is proposed. Thirty minutes after a paced circuit training, a visual-auditory task was presented for 40 min: tachistoscopically presented dot patterns together with high and low tones. This was done at an easy pace, leaving it up to the subject to decide what to reproduce, as in normal circumstances. No effect was found in the total correct scores or in the auditory task. Deterioration was found only in the more difficult part of the visual task. The results can be explained in terms of Kahneman’s variable-allocation capacity model. This method seems promising for separating effects on different stages of information processing.

Spatial compatibility with a two-dimensional stimulus arrangement

In this study, spatial compatibility of two-dimensional stimulus arrays versus one-dimensional response and effector arrays was investigated. A two-choice reaction time task was performed with rotating stimuli arranged on the periphery of a black vertical disk. Response was bimanual, with a crossed- and uncrossed hands condition. Depending on the cues presented, subjects tended to use different relations in responding. Furthermore, it was demonstrated that a second dimension in the stimulus arrangement could improve performance in some situations, especially if the transposition of dimensions was facilitated by spatial cues.

Traces of fatigue in an attention dual task: II

Effects of physical effort have been difficult to trace in attention tasks for various reasons, such as the activating effect of the laboratory situation or the spare capacity in automated tasks. Instead, Vervaeck, Deboeck, Hueting, and Soetens (1982) proposed a dual task, reflecting quantitatively the changes that take place in the processing of information when fatigue is introduced. This is a follow-up paper with a similar method; that is, a visual-auditory dual task is presented 30 min after physical effort. The results revealed that the deterioration of performance in the more difficult part of the visual component of the task, found in the previous study, was not due to an increased distraction of fatigued subjects, but rather to a shortage of allocatable capacity. It is suggested that parallel processing occurs with one fast processing line, which is used for evaluating the requirements of the task. Combining this information with an estimation of the available allocatable capacity, subjects decide to continue or to interrupt the processing of the stimulus.