Transient stimulation does not aid visual search: Implications for the role of saccades

Previous demonstrations that performance on visual search tasks with briefly flashed presentations declines over time after the initial onset imply that saccades might be necessary for efficient acquisition of visual information. We imposed an additional abrupt onset and a displacement on character arrays containing letters and one numeral while subjects searched for the numeral. Presentations were always followed by a visual noise field. Presentation time varied (50–800 msec). We found that performance with presentations containing one onset and remaining continuously visible was better than performance with presentations containing two onsets and containing displacements. Furthermore, information acquired near the onset of a continuous presentation was as effective as information acquired later. Our results demonstrate that abrupt onsets and displacements do not improve information acquisition with displays of alphanumeric characters. This finding is consistent with earlier reports that saccade-like retinal image motion does not contribute either to the maintenance of target visibility or to visual acuity.     

ACQUISITION OF SIGN LANGUAGE BY AUTISTIC CHILDREN. I: EXPRESSIVE LABELLING

There has been growing interest in teaching sign language to autistic children who have failed to develop speech. However, controlled experimentation in this area is nonexistent. In the present study, four nonverbal autistic children were taught expressive sign labels for common objects, using a training procedure that consisted of prompting, fading, and stimulus rotation. The efficacy of the procedure was demonstrated in a multiple-baseline design across objects. The results were reliable, replicable across children, and generalizable across therapists. A stimulus control analysis demonstrated that, for three of the children, correct signing was controlled solely by the visual cues associated with the presentation of a given object and was independent of the auditory cues related to the same object. These latter results are discussed with respect to the known perceptual and linguistic deficits of autistic children.     

Narcissism and the self in homicidal adolescents

Even where it emerges without any sexual purpose, in the blindest fury of destructiveness, the satisfaction of an instinct is accompanied by an extraordinarily high degree of narcissistic enjoyment? owing to its old wishes for omnipotence.     

Signal probability, reinforcement and signal detection.

Five pigeons were trained to detect differences in light intensity. Two stimuli, S1 and S2, differing in intensity, were arranged on the center key of a three-key chamber according to set probabilities. A peck on the center key turned on the two side keys. When S1 was presented on the center key, a peck on the left key was "correct" and when S2 was presented, a peck on the right key was "correct." Correct responses produced reinforcement and incorrect responses produced 3-second blackout. Detection performance was measured under three procedures. The first was a standard signal-detection design in which the probability of S1 was varied and the number of reinforcements obtained for correct responses to S1 was allowed to covary. In the second procedure, the probability of S1 was again varied but the distribution of reinforcements between the two choices was kept equal. In the third procedure, probability of S1 was held constant while the distribution of reinforcements was varied between the two choices. Changes in response bias were a function of variations in the relative reinforcement ratio for the choice responses and not a function of variations in the probability of stimulus presentation. Discriminability remained constant across the three procedures.     

Formal,systematic, and metasystematic operations with a balance-beam task series: A reply to Kallio's claim of no distinct systematic stage

This reply discusses the measurement of formal, systematic, and metasystematic stages. Recent multidomain studies have shown disparate results and we suggest that these results could be attributed not to actual variations in adult development or the existence or non-existence of stage, but instead may reflect differences in methodology regarding task, domain, and scoring. Our study indicates that when tested in only one domain—balance beams and extensions of those tasks—participants who performed at the higher stage were also able to perform at the lower stages. These results also coincide with similar studies conducted.     

Adaptive executive control: Flexible multiple-task performance without pervasive immutable response-selection bottlenecks

A new theoretical framework, the EPIC (Executive-Process/Interactive-Control) architecture, provides the basis for accurate detailed computational models of human multiple-task performance. Contrary to the traditional response-selection bottleneck hypothesis, EPIC's cognitive processor can select responses and do other procedural operations simultaneously for multiple concurrent tasks. Using this capacity together with flexible executive control of peripheral perceptual-motor components, EPIC computational models account well for various patterns of mean reaction times, systematic individual differences in multiple-task performance, and influences of special training on people's task-coordination strategies. These diverse phenomena, and EPIC's success at modeling them, raise strong doubts about the existence of a pervasive immutable response-selection bottleneck in the human information-processing system. The present research therefore helps further characterize the nature of discrete versus continuous information processing.     

Effects of the discriminability of alternatives in three-alternative concurrent-schedule performance

Six pigeons were trained on two- and three-alternative concurrent schedules in which the alternatives were signaled by different wavelengths of light on the main pecking key. The schedules were arranged according to a switching-key procedure in which pecks on a white side key produced a 3-s blackout and, intermittently, a change in the variable-interval schedule of food programmed on the main (center) key after the blackout. In Part 1, a two-alternative concurrent variable-interval schedule was arranged in which the alternatives were signaled by 560 nm and 630 nm. Parts 2 and 3 arranged three-alternative concurrent variable-interval schedules with the alternatives signaled by 560 nm, 600 nm, and 630 nm (Part 2) and 560 nm, 623 nm, and 630 nm (Part 3). Within each part, the relative rate of food reinforcers available on the alternatives was varied across a wide range. In all parts of the experiment, the ratios of responses emitted between pairs of alternatives were more extreme than the ratios of reinforcers obtained on the pairs of alternatives, a result termed overmatching. In Parts 2 and 3, generalized matching sensitivities between pairs of alternatives were found to be higher when the reinforcer rate on the third alternative was low than when it was high—an apparent failure of the constant-ratio rule. The data were well described by an extension of the Davison and Jenkins (1985) model, which assumes differing discriminabilities between concurrent-schedule alternatives in combination with a punishing effect of blackout following changeovers.     

Effectiveness of the counterconditioning procedure in eliminating avoidance behavior

Data were obtained on the effectiveness of three forms of counterconditioning—each differing in the degree to which competing responses were introduced. Counterconditioning was also compared with an extinction procedure in eliminating an instrumental avoidance response. Only the counterconditioning procedure which evoked and reinforced another conditioned response during extinction of the avoidance response, was significantly more effective than a traditional extinction procedure in achieving a decrement in avoidance responding and this was only on the first session on which such procedures were in effect. When the opportunity to perform the competing response was removed, only Ss in this group evidenced a significant increase in avoidance responding.

All procedures were equally effective over sessions in eliminating avoidance behavior. A delay in effectiveness occurred to the degree to which a procedure introduced a competing response. It was in terms of the immediacy of response reduction and achievement of a very low rate of responding with very few responses being performed, that the counterconditioning procedure was superior to the extinction procedure.

The implication of these results for behavior theory and therapy were elaborated.