Showing papers in "Journal of Experimental Psychology in 1966"

Conservatism in a simple probability inference task.

Abstract: 3 experiments investigated the effects on posterior probability estimates of: (1) prior probabilities, amount of data, and diagnostic impact of the data; (2) payoffs; and (3) response modes. Ss usually behaved conservatively, i.e., the difference between their prior and posterior probability estimates was less than that prescribed by Bayes' theorem. Conservatism was unaffected by prior probabilities, remained constant as the amount of data increased, and decreased as the diagnostic value of each datum decreased. More learning occurred under payoff than under nonpayoff conditions and between-S variance was less under payoff conditions. Estimates were most nearly Bayesian under the (formally inappropriate) linear payoff, but considerable overestimation resulted; the log payoff condition yielded less conservatism than the quadratic payoff. Estimates were most nearly Bayesian when Ss estimated odds on a logarithmic scale.

Use of a delayed signal to stop a visual reaction-time response.

Abstract: In a visual RT experiment, 5 male Ss were each confronted with 2lights and instructed to respond to 1 light but not respond whenboth lights occurred. The onset of the 2 lights was made asynchronousby 0, 12, 33, or 63 msec. Probability of inhibiting the responsedeclined markedly for each delay and increased with RT. It was con-cluded that choice RT is correlated with the extent of the stimulusinformation processing and the duration of effective stimulation whichhas preceded initiation of the motor event.

Premotor and motor components of reaction time.

Abstract: Reaction time (RT) was fractionated into premotor and motor components based upon the difference between EMG and finger-lift responses. EMGs were recorded from the extensor muscle of the responding forearm during measurement of simple auditory RTs of 54 Ss. The premotor time was that period from the presentation of the stimulus to the appearance of increased muscle firing, while the motor time was that period from this change in action potential to the fingerlift response. 4 preparatory intervals (PI), 0.5, 3.0, 6.0, and 15.0 sec., were used in both a regular and irregular series. Premotor time and RT were highly correlated and showed comparable variations as a function of PI and type of series. Motor time was poorly correlated with RT and was independent of PI and type of series. It was concluded that set, as inferred from the relations between RT and PI and type of series, is a premotoric process.

Visual and proprioceptive adaptation to optical displacement of the visual stimulus.

Abstract: The effects of long-term optical displacement of the visual stimulus were measured in a wide variety of sensory coordinations. The pattern of changes observed indicated that a transient adaptation in the proprioceptive system is succeeded by a stable adaptation in the visual system. It was found that viewing the whole body during optical displacement, rather than just a part of it, serves to induce the visual adaptation.

Adaptation to displaced and delayed visual feedback from the hand.

Abstract: S viewed an oscilloscope trace of a short bar which appeared at the position of his nonvisible right hand. The motion of the trace was equivalent to the movements of the hand, which were restricted to a frontal plane. The bar could be optically displaced by 20 diopter prisms, either to the left or right, and its motion could be made to lag behind that of the hand by 1 of 6 delay intervals ranging from 0.0 to 3.0 sec. Results show that the adaptation to displacement found with no delay is completely eliminated under all delay intervals, including the minimum of 0.3 sec.

Clustering in free recall as a function of certain methodological variations.

Abstract: : Three experiments involving category clustering in lists composed of high-frequency (HF) and low-frequency (LF) associates of the category names are reported. The major results were: 1. Block presentation augments clustering in both lists and augments word recall in HF but not in LF lists. 2. Word recall and clustering are higher in HF lists than in LF lists. 3. Duration of item presentation interval augments both clustering and word recall within limits. 4. An immediate recall augments or maintains clustering and word recall on a second recall, obtained after a short delay. 5. These findings and certain interactions are discussed with respect to the interpretation of recall of categorized lists. It is concluded that a coding hypothesis cannot do justice to all the findings. Associations between the category names and their instances or among the instances themselves are suggested as supplemental or alternative mechanisms. (Author)