James L. Knight

Inferring decay in short-term memory: The issue of capacity.

Experiments examining the issue of decay in short-term memory have assumed a single undifferentiated source of processing capacity which cannot be devoted to rehearsal when consumed in the processing of a nonverbal interpolated task. Three experiments reported here call this logic into question, since variations in difficulty in the nonverbal interpolated task failed to affect recall. Slight forgetting produced by a nonverbal interpolated task, relative to a no interpolated task control, was attributed to qualitative differences from performing two tasks simultaneously rather than only one. Results from the third experiment indicated that retrieval after a period of nonverbal interpolated activity is from primary rather than secondary memory.

Effects of task feedback and stringency of external pacing on mental load and work performance

Sixteen subjects were used to study the effects of two levels of pacing constraint and four performance feedbacks on the performance and menial load associated with a manual task. The following main conclusions emerged: (1) performance feedback reduces the mental load of the task only when the pacing constraint is low and (2) feedback improves task performance when the pacing constraint is low since operators are able to meet work requirements more closely. Feedback, however, does not improve the performance or reduce the mental load of a highly paced task

Speed-accuracy tradeoff in double stimulation: Effects on the first response

A single-stimulation and two double-stimulation response conditions were compared using explicit payoff matrices to vary speed-accuracy tradeoff. Under accuracy payoff, response latency (RT1) to the first stimulus increased as ISI dropped but accuracy remained high and relatively constant. Under speed payoff, RT1 was only slightly affected by ISI but accuracy dropped as ISI decreased. Transmitted information rates consistently reflected detrimental effects of short ISI. In double stimulation, but not in single stimulation, error response latency exceeded correct response latency. Furthermore, error response latencies were found to be far more variable and more sensitive to changes in speed-accuracy condition than were correct response latencies. Finally, under both speed and accuracy conditions, response latency to the first of two successive stimuli was faster if a response was also required to the second stimulus. Implications of the data for possible models of double-stimulation speed-accuracy tradeoff are considered.

A minicomputer method for generating dichotic word pairs

A computer method is described for generating dichotic word pairs. The Purdue Laboratory system is implemented with a DEC PDP-12 computer.

Impact of personality and intelligence on job satisfaction of assembly line and bench work - an industrial study.

A study of the impact of machine-paced (M/P) and self-paced (S/P) work on job satisfaction of 28 female industrial assembly workers was evaluated in which M/P work was confounded with simplified work and the S/P job was confounded with enriched tasks. Results indicated the following: 1. Over three-quarters of workers were more satisfied in S/P jobs, while only less than one-quarter were more satisfied in M/P jobs. 2. The 16PF personality test effectively predicts (0.88 multiple correlation) the satisfaction ratios of M/P to S/P jobs.

Speed-accuracy tradeoff in double stimulation: II. Effects on the second response

In the double-stimulation paradigm subjects respond to two successive stimuli. Previous research (Knight & Kantowitz, 1974) showed that a subject’s speed-accuracy tradeoff (SAT) strategy interacted with the interval between the two stimuli to determine response performance to the first stimulus. The present experiment examined the influence of SAT strategy on response performance to the second stimulus. Interest focused on effects of SAT strategy upon the psychological refractory period (PRP) effect. If a single mechanism underlies beth first-and second-response performance (e.g., the PRP effect) in double stimulation, effects of SAT upon the second response should be similar to effects upon the first response. Results showed that the PRP effect appeared only when second-response accuracy was stressed. Under speed emphasis double-stimulation second-response latency never exceeded a single-stimulation baseline. This was analogous to first-response latency effects found by Knight and Kantowitz (1974). Response grouping was strongly influenced by SAT strategy and two response-grouping mechanisms were distinguished. Implications of these and interresponse time data for models of double-stimulation performance are discussed.

Circulatory responses to machine-paced and self-paced work: an industrial study

In a statistically balanced experimental design, 36 experienced industrial operators performed the same light assembly task in machine-paced (M/P) and self-paced (S/P) modes. The task was performed for 2 weeks in each pacing condition. Data was collected continuously for the following variables: heart rate; and systolic, diastolic and physiological mean blood pressures. Neither statistically significant nor clinically meaningful differences were found between the M/P and S/P mode.

Physiological basis of machine-paced and self-paced work

Currently, the majority of the machine-paced jobs in industry are manned by younger workers while older workers are predominantly working on self-paced work. Laboratory research suggests the hypothesis that the above policy of allocating people to jobs results in lower physiological efficiency of the human body than may be possible to achieve through new policies of job design and manpower allocation procedures. Hence, this study is proposed to test the above hypothesis in industrial work situations. In a statistically balanced, designed experiment 33 female operators, representing the age range of 28 to 64 years, performed in industry the same task at both machine-paced and self-paced performance for a total duration of four weeks. During the period of this experimentation, data was collected and analyzed on physiological costs (sinus arrhythmia, mean heart rate, blood pressure and rate of breathing) associated with the machine-paced and self-paced operation. Results are discussed for the following: (1) comparisons between the stress levels associated with machine-paced and self-paced work for the younger and the older subjects, and (2) changes, over the working day, in work capabilities of operators which significantly effect the stress levels in work situations. Methodologies are proposed, the implementation of which may result in reduction of stress at work.

Attitudinal, personality, and age characteristics for machine-paced and self-paced operations

In studying the personality, attitude and subjective feelings of 33 female operators regarding their jobs, the following is concluded: that workers with specific identifiable attributes are more suited for machine-paced work than people having different attributes; attributes of people most suited for self-paced work are also identified. These attributes are detailed and discussed.

Locating and Reducing Cognitive Load in Paced and Unpaced Tasks

Heart rate variability often decreases with increased cognitive load (Kalsbeek, 1971). Studies (Manenica, 1977) varying task pacing requirements unexpectedly revealed decreased SA in self-pacing (self-controlled intra-task event timing) compared to external-pacing (experimenter- or apparatus-controlled event timing). But why should self-pacing ever involve higher cognitive load? Since Ss must time events and otherwise monitor and structure their own performance in self- but not external-pacing, perhaps these responsibilities lead to higher cognitive load in self-pacing when work-rates are equated between self-and externally-paced conditions. Two experiments were conducted to examine possible sources of cognitive load in self-pacing. In Experiment II, an attempt was made to reduce cognitive load by providing new sources of extrinsic feedback on a visual display. In both studies physical work load was held constant across experimental conditions.