Variations in watch keeping performance as a function of the rate and duration of visual signals

This study was designed to assess the relative effects on watch keeping performance of five signal durations (0.5, 1.0, 2.0, 4.0, and 8.0sec) combined factorially with five signal rates (6, 12, 24, 48, and 96 sig/h). A visual display consisting of a red and green light mounted on a vertical vector was used; red-onset and green-offset were critical signals. The probability of correct detections increased monotonically with increases in signal duration; a stable rate of nearly 100% detection was approached at signal durations of 4.0 and 8.0 sec, independently of signal rates. The likelihood of detection was enhanced by increases in signal rates only at the 0.5-sec duration with the green-offset critical signal. Response time to correct detections increased with time on watch, independently of signal rates and durations.     

Haptic identification of letters using the left or right hand

The present study investigated the effects of the use of the right and left hands on haptic identification of letters of the alphabet. Each of the 64 right-handed subjects was given three series of randomly ordered presentations of the 26 letters of the alphabet. The subjects were asked to feel each letter and name correctly each letter as quickly but as accurately as possible. Analysis showed faster identification by those subjects using their left hands on Series 1 with no hand-differences appearing on Series 2 and 3. Significant over-all improvement in identification time occurred with practice. The results were interpreted in terms of a novelty hypothesis of right-hemisphere function and an explanation of perceptual learning of letter identification.     

A cognitive-psychological perspective on Gillespie's "Lights and lattices": some relations among perception, imagery, and thought

George Gillespie's valuable observations on light and lattice imageries are played in the context of current research and theory on cognitive imagery (Kosslyn, Pylyshyn), ordinary and lucid dreaming, representational geometric imagery in scientific thought, the author's previous writings on altered states of consciousness, and Gibson's views on perception and imagery. Gillespie's reports show categories of imagery deconstruction and abstraction that link these areas and suggest an integrative model of the varieties of symbolic imagery.     

Individual differences in secondary task performance

The purpose of this research was to use secondary task performance as a predictor of performance on a difficult primary task. Reaction time (RT) to secondary probes that occurred during the rehearsal period of an easy memory task were used to measure spare capacity associated with the memory task. This measure was then correlated with performance on a harder version of the same memory task. Experiments 1-4 involved a paired associate memory task. Probe RT was sensitive to the difficulty of the paired associate task, and analysis of individual differences showed that probe RT during the easy version of the task was correlated with performance on a harder version of the task. Experiment 4 also utilized a spatial memory task. Probe RT was less sensitive to the demands of the spatial memory task, and in that case, the "easy-to-hard" prediction was not successful.     

Effects of stimulus-response uncertainty on watchkeeping performance and choice reactions

The present study was conducted to assess the effects of S-R uncertainty on performance in watchkeeping and typical type-b choice-reaction situations. The assessment was based in part on measurements of S-R compatibility effects in the two performance conditions. Four levels of S-R uncertainty (1, 2, 3 and 4 bits/S-R event) were combined factorially with two levels of S-R compatibility (high and low) and the two kinds of tasks (watchkeeping and choice-reaction); 12 Ss were assigned at random to each of the 16 conditions. A matrix of lights was used as stimuli in the choice-reaction condition; Ss monitored the matrix for a I-h duration in the watchkeeping condition. In both tasks, Ss responded by pressing a corresponding key after the presentation of a stimulus or “critical signal.” Reaction time (RT) was found to be an increas ing linear function of S-R uncertainty in both tasks. and the effects of S-R compatibility were essentially identical in the two. However, choice reactions were significantly faster than watchkeeping responses, and the rate of gain of information in watchkeeping was greater than in the comparable choice-reaction situations. The results are interpreted as supporting the hypothesis that watchkeeping differs from the simpler choice-reaction task principally in presenting an additional source of (temporal) uncertainty for information processing.     

Effects of discriminability and irrelevant information on absolute judgments’

The effects of irrelevant information (0, 1, 2, or 3 bits stimulus) on absolute judgments of size were measured at different levels of discrimination difficulty. The stimuli were 7 small circular spots of light of different sizes, selected from an eaual-discriminability scole, and arranged into 6 pairs that represented different levels of stimulus dissimilarity. Three of the pairs comprised a low-dissimilarity (LD) subgrouping in which different lepels of dissimilarity and discriminability were confounded, whereas the remaining three pairs comprised a high-dissimilarity (HD) subgrouping in which different levels of dissimilarity occurred at a single high level of discriminability. Different colors were used to provide the four levels of irrelevant information; 240 Ss (10 in each of the 24 experimental conditions) made absolute judgments of size under the classical procedure for the method of single stimuli. Separate analyses of errors, reaction times, and rates of information transmission indicated that irrelevant information had an increasingly detrimental effect on absolute judgments as discrimination difficulty was increased (in the LD subgroup), but essentially no effect where discriminations were easily modefin the HD subgroup).