The equivalence of target and nontarget processing in visual search

A comparison of a forced-choice visual search task with an item recognition task did not support Neisser’s (1967) hypothesis of a preattentive stage that processes targets and nontargets differentially. In the forced-choice condition, Ss indicated which of two items in a visual display was a target; in item recognition, Ss determined whether or not the single item in the visual display was a target. The size of the memorized set of possible targets was varied from one to six items for both tasks. Latencies increased linearly with memory set size in both conditions; the slopes for forced choice and item recognition were 41.8 and 27.9 msec per item, respectively. The ratio of 1.38 between the two slopes was well fit by Sternberg’s (1967) item recognition model, which predicts a ratio of 1.50.     

A comparison of two methods of measuring conditioned taste aversions

Two methods of measuring conditioned taste aversions were compared. Following adaptation to a daily 10-min water drinking schedule, rats were made ill with an injection of cyclophosphamide after presentation of a novel-tasting fluid. Three days after this treatment, Ss were tested by (1) measuring the amount of the novel fluid consumed on the continuing 10-min access schedule or (2) measuring their preference between plain water and the novel fluid. When the drinking behavior of the conditioned animals was compared with that of appropriate controls, the preference method proved to be the more sensitive.     

Auditory generalization gradients for response latency in the monkey

Two monkeys were trained to press and hold a response key in the presence of a light and to release it at the onset of a pure tone. Initially, all responses with latencies shorter than 1 sec were reinforced without regard to the frequency of the pure tone, and the intensity of the pure tone that resulted in equal latencies at each frequency was determined. The second stage of the experiment consisted of discrimination training, during which releases to one pure-tone frequency (positive stimulus) were reinforced and releases to a second frequency (negative stimulus) were extinguished. Median latencies to the negative stimulus slowly increased as did the variability of the latency distribution for the negative stimulus. There was no evidence of a concurrent decrease in latencies to the positive stimulus indicative of behavioral contrast. The third part of the experiment consisted of determining maintained generalization gradients by increasing the number of nonreinforcement stimuli. The gradients that eventually resulted showed approximately equal latencies to all frequencies of the negative stimulus and shorter latencies to the positive stimulus frequency.     

Further studies on the psychophysics of irregular nerve action potential patterns

In this paper we consider two problems concerning human psychophysical discriminability of variable interval nerve action potential patterns. The first question asks which of two possible alternatives-additional sample size or elongation of duration-is responsible for the improvement in performance as the number of pulses in a stimulus train increases. Our data strongly indicated that the answer to this question is increased sample size. The second question concerns what effect, if any, parallel rather than serial presentation of the two alternatives in a forced choice psychophysical test will have on the function relating interpulse interval and discriminability. The answer to this question appears to be that other than a slight elevation of the absolute levels no changes in the general form of the response is produced.     

SCORIT: A computer subroutine for scoring electrodermal responses

Given digitized electrodermal response records sampled at a rate of 20/sec and at a sensitivity level between 140 and 170 ohms, a computer subroutine for scoring skin resistance responses is described. It is designed to score multiple responses on a trial, which makes it particularly suitable for classical conditioning experiments involving long interstimulus intervals. The subroutine returns to the main program response latency, base resistance, peak resistance, and time from base to peak. Since SCORIT is written in FORTRAN IV, it can be employed in virtually any modern central computing facility at costs substantially below those involved in hand scoring.