Neural control of behavior: countermanding eye movements

Understanding the self-control of action entails knowledge about how actions are initiated, how planned actions are canceled and how the consequences of actions are registered. We have investigated neural correlates of these processes using the countermanding paradigm – a task that required subjects to occasionally cancel a planned speeded response, and an analysis that provides an estimate of the time needed to cancel a planned movement. By monitoring the activity of single neurons in the frontal cortex of macaque monkeys performing this task we have distinguished signals responding to the visual stimuli, other signals that control the production of movements, and still other signals that seem to monitor behavior. Received: 31 March 1999 / Accepted: 23 July 1999     

The role of verbal behavior in human learning: III. Instructional effects in children

Lever pressing of children from three age groups (2½ to 4, 5 to 6½, and 7½ to 9 years) could produce reinforcers according to a fixed-interval 40-s schedule: (1) Some were instructed to respond at a high rate, others at a low rate, and (2) they were subsequently taught to provide their own spoken self-instructions consonant with the earlier, experimenter-supplied instructions. All subjects who received high-rate instructions responded at a steady, high rate, which was maintained following self-instructional training. The effects of low-rate instructions were directly related to the age of the children. The two older groups produced low-rate patterns, with the oldest children responding at very low rates; effects were least noticeable in the youngest age group. Following self-instructional training, all three groups showed adult-like low-rate behavior and the oldest children showed an improved ability to estimate the interval length. The results provide further evidence of the importance of language as a determinant of human behavior.     

Sustained attention in combat-related posttraumatic stress disorder

There is substantial evidence that PTSD patients have information processing abnormalities for stimuli that are highly relevant to the traumas they have endured. The goal of the present study was to examine whether this extends to neutral stimuli as well. Twenty-four male Vietnam combat veterans with PTSD were compared to fifteen normal male comparison subjects on their performance on a sensitive measure of sustained attention, the Continuous Performance Test-Identical Pairs version (CPT-IP). PTSD subjects did not differ from controls in their ability to discriminate target stimuli from background noise on the CPT. Additionally they performed as well as controls, even in the presence of external distraction. Thus, this study did not find a generalized deficit in attention associated with PTSD on the CPT-IP. Nevertheless, further clarification of the nature of the information processing disturbance in PTSD is warranted.     

Cognitive theory,cognitive impairment and clinical practice

The aim of this paper is to present a practical model for investigating cognitive impairment which integrates the experimental-cogaitive-information processing-theory and the psychometric-intellectual-abilities-tradition in psychology to understanding cognitive functioning. It reviews developments in cognitive theory in terms of Processes, complex and simple, such as Intelligence and Information Processing, and Factors of attained Level and Learning ability in the Verbal and Performance modalities. The Savage Cognitive Impairment Model (SCIM) is outlined and types of cognitive impairment defined. Measures of cognitive impairment relevant to clinical practice and research are presented.     

Processing of information about location in brief visual displays

Within the context of the selective masking effect (Merikle, Coltheart, & Lowe, 1971), a series of five experiments investigated the utility of bar-marker probes as a poststimulus sampling procedure for partial report of brief visual displays. It was demonstrated that bar markers are inadequate as partial-report cues because subjects cannot properly locate the positions of the probes. An improved bar-marker procedure was developed which removed this problem of cue localization. Furthermore, it was shown that subjects, when given the opportunity, are able to report much more from brief visual displays than the bar-marker procedure typically permits. It was also suggested that subjects’ ability to employ bar-marker probes is governed by quite different factors than their capacity to report the contents of brief visual displays.     

The effect of stimulus person valence on divergent self-other attributions for success and failure

Two experiments investigated self-other attributions for success and failure. In Experiment 1, high and low achievers completed a modified IAR scale either for themselves or another. Regardless of achievement motives, more personal attribution for failure was assigned to oneself than to a neutral other. In Experiment 2, additional scales for liked and disliked others were administered and scale item importance was varied. On global and individual causal measures, neutral and liked others were credited more and disliked others less for success than oneself, and liked others were blamed less and disliked others more for failure than oneself and neutral others. Item importance produced few effects. Results were interpreted in terms of informational considerations in self-other attribution.     

The role of verbal behavior in human learning: infant performance on fixed-interval schedules

The performances of two infants less than one year old were investigated on fixed-interval schedules. When the infants touched a cylinder either music or food was presented according to fixed-interval schedules ranging in value from 10 to 50 seconds. With respect to two principal criteria, namely, pattern of responding and sensitivity to the schedule parameter, the subjects' behavior closely resembled that of animals but differed markedly from that of older children and adults. Negatively accelerated responding in the course of the fixed interval in the early sessions gave way to a scalloped pattern, consisting of a pause after reinforcement followed by an accelerated response rate. This scalloped pattern was the final form of responding on all schedule values. Analysis of data after performance had stabilized showed that postreinforcement pause was a negatively accelerated increasing function, and running rate (calculated after excluding the postreinforcement pause) was a declining function, of schedule value. On each schedule, the durations of mean successive interresponse times declined in the course of the fixed interval and were directly related to schedule value. The results supported Lowe's (1979) suggestion that verbal behavior may be responsible for major differences in the schedule performance of older humans and animals.