Discrimination of time intervals marked by brief acoustic pulses of various intensities and spectra

Experienced observers were asked to identify, in a four-level 2AFC situation, the longer of two unfilled time intervals, each of which was marked by a pair of 20-msec acoustic pulses. When all the markers were identical, high-level (186-dB SPL) bursts of coherently gated sinusoids or bursts of band-limited Gaussian noise, a change in the spectrum of the markers generally did not affect performance. On the other hand, for 1-kHz tone-burst markers, intensity decreases below 25 dB SL were accompanied by sizable deterioration of the discrimination performance, especially at short (25-msec) base intervals. Similarly large changes in performance were observed also when the two tonal markers of each interval were made very dissimilar from each other, either in frequency (frequency difference larger than 1 octave) or in intensity (level of the first marker at least 45 dB below the level of the second marker). Time-difference thresholds in these two latter cases were found to be nonmonotonically related to the base interval, the minima occurring between 40- and 80-msec onset separations.     

Historical comparisons: Testing psychological hypotheses with cross-era data (1)

Cross-era research, an approach which involves developing and testing social science hypotheses in terms of historical time-series data, is first discussed as regards its relationship to other comparative research approaches. Some examples of cross-era research in psychology are described. Special problems that arise in cross-era research, and proposed methods of coping with them, are discussed as regards each of the three successive phases of research: creative hypothesis formation problems; difficulties that arise in the hypothesis-testing phase; and problems that emerge during the phase of communicating and utilizing the findings.     

Stimulus redundancy and immediate recall

This study examined immediate recall in two stimulus prefix and two stimulus suffix conditions and in a condition that combined a prefix and suffix. Suffixes and the combination of a prefix with a suffix interfered more with recall overall than did prefixes. Performance in each of the conditions that included a prefix was significantly better overall than in appropriate control conditions, in which interference was augmented by a redundant element in recall. It was suggested that prefixes and suffixes lie operationally on a continuum and that their effects result from the subject's inability to dissociate the redundant element from the memory series. However, the location of redundancy imposes different processing requirements that differentially influence recall.     

Manipulation of response-contingent unconditioned-stimulus intensity in human eyelid conditioning: A two-phase model analysis

Four groups of human subjects were given 360 classical eyeblink conditioning trials. All groups received the same UCS (unconditioned stimulus) intensity on[Formula: see text] (nonconditioned response) trials but differed in the intensity presented on CR trials. Response probability increased as a positive function of UCS intensity on CR trials. Phase 1 of the two-phase model was longer when no UCS was presented on CR trials, but did not differ in duration among the remaining three groups. Most subjects could be described with a single operator in Phase 2, the operator limit increasing as a positive function of CR-contingent UCS intensity. For subjects requiring different operator limits on CR and[Formula: see text] trials, the latter was lower with high CR-trial intensities but higher with low CR-trialintensities. The results were interpreted to be more consistent with drive theory than with "law-of-effect" or two-factor theories.     

Control-system theory and performance objectives

Behaviorism, the source of the concept of performance objectives, models behavior as an output emitted by an organism. Control theory suggests a different model, in which the stable patterns called behavior are perceptual variables stabilized against disturbances by variations in motor activities. Control theory provides a clear distinction between a learning model and a performance model. Learning is centered around the control of internal variables by means of changes in the organization of performance. Performance is centered around control of perceptual variables, which the experimenter or teacher must learn to share with the subject or student in order to understand what is being performed.