Short-term visual storage

The delay between the offset of a briefly exposed array of letters and digits and the onset of an arrow pointing at one of the array positions was varied from 0 to 5000 msec. In addition, the luminance of the stimulus array was varied over three levels. The Ss reported the item in the position indicated by the arrow. Luminance, delay, and the luminance by delay interaction were all significant I Performance monotonically decreased from a delay of 0 msec to a delay of 250 msec, but the percent correct remained fairly constant from 250 msec to 5000 msec. With delays shorter than 250 msec, high luminance arrays showed better performance.     

Strategies and learning models

A class of strategies is defined, each member of which possesses a certain plausibility. If a subject follows any strategy in this class in a two-choice learning experiment of the type dealt with by the Estes model, the subject's long-run behavior will be the same as that predicted by the Estes model.     

Do perception and motor production share common timing mechanisms: A correlational analysis

The two experiments of this study exploited individual variation in timing ability to ask whether the production of time intervals by different motor effectors and the judgement of perceptually based time intervals all share common timing mechanisms. In one task subjects produced a series of taps, attempting to maintain constant intervals between them. Individual differences in variability of the produced intervals correlated across the effectors of finger and foot. That is, people that were ‘good timers’ with one effector tended to be ‘good timers’ with another. Besides timing motor production, the subjects also judged durations of brief perceptual events. The acuity of perceptual judgements correlate substantially with regularity of motor production. Further results involving maximum speed of motor production suggested that variability of motor timing comes from two sources, one source in common with perception, and hence called clock variability, and the other source in common with motor speed, and hence called motor implementation variability. The second experiment showed that people high in skill on the piano were better at both types of timing on the average than control subjects with no expertise.     

Sex differences on the Wechsler preschool and primary scale of intelligence

Male-female differences on the Wechsler Preschool and Primary Scale of Intelligence were examined for 1200 children aged 4–6.5 yr. Results provided fundamental support for previous work with older children showing better female performance on memory and psychomotor tasks and better male performance on spatial tasks, although the distinctions in performance were not as clear as with older children.     

The role of prior knowledge in explaining hypothetical events

Having subjects explain a hypothetical future event biases their subjective likelihood estimates for that event. However, Sherman, Zehner, Johnson, and Hirt (1983, Journal of Personality and Social Psychology, 44, 1127–1143) found that the biasing effects of an explanation task were reduced when subjects formed an initial impression based on the information (prior to the explanation task). Nonetheless, there are no doubt many factors that may influence subjects' ability to form strong initial impressions. The present studies address two of these factors. Experiment 1 used both subjects who were knowledgeable and unknowledgeable (naive) about a stimulus domain (football). Experiment 2 used only knowledgeable subjects, but gave these subjects information about unfamiliar teams and players. Subjects first read information about teams in an upcoming game and were then asked to explain a hypothetical victory by one team. They then made judgments about the actual future game and recalled the information. Only knowledgeable subjects given an initial impression set and given information that was easily integrated with past knowledge were able to resist the explanation bias. All other subjects demonstrated judgments that were strongly biased in the direction of the outcome explained. An examination of the relation between judgment and recall implied that knowledgeable and naive individuals differed in the ways they made judgments.     

Dynamic changes in work/rest duty cycles in a study of sleep deprivation

The effects of moderate workload and 72 h of sleep deprivation were studied using a modified continuous-performance paradigm. Ten subjects were tested hourly on a number of perceptual and cognitive tasks designed to require approximately 30 min to complete, with the remainder of each hour free. As sleep deprivation continued, the average time on task increased at an accelerating rate. The rate of increase differed among tasks, with longer tasks showing greater absolute and relative increases than shorter ones. Such increases confound sleep deprivation and workload effects. In this paper, we compare the advantages and disadvantages of several experimental paradigms; describe details of the present design; and discuss methodological problems associated with separating the interactions of sleep deprivation, workload, and circadian variation with performance.     

Resistance to extinction following habituation to behaviourally disruptive novel stimuli

Three experiments tested the prediction, derived from generalized frustration theory (Amsel, 1972), that habituation to behaviourally disruptive stimuli increases resistance to extinction in the runway. In each experiment, rats received initial consistent reinforcement (CRF) training and then either continued CRF (Groups C), partial reinforcement (PRF) training (Groups P), or CRF accompanied by presentations of a novel tactile, tone, or obstacle stimulus (Groups D) in Experiments 1-3, respectively. PRF increased resistance to extinction whether non-reinforcement disrupted behaviour (Experiment 1) or not (Experiments 2 and 3). The tactile and obstacle stimuli very substantially disrupted behaviour, and the tone produced a modest disruption of behaviour. All subjects habituated to the disruptive effects of these stimuli, but Group D was not more resistant to extinction than Group C in any experiment. The results suggest that non-reinforcement has unique stimulus properties, a consequence of which is that habituation to other sources of disruptive stimulation does not promote responding to non-reinforcement in extinction.     

Short report: Object-centred inhibition of return of visual attention

Our response to visual events can be delayed at positions we have recently examined attentively. Such inhibition could organize visual search through static scenes by suppressing those loci already searched, but this mechanism would fail in moving scenes as objects' locations then change during search. We cued attention to a moving object and found subsequent inhibition at the locus the object later occupied. This implies that previously examined objects are suppressed. Such object-centred inhibition would be highly adaptive, but would require a sophisticated neural implementation for a mechanism held to be sub-cortical.