Glen H. Egstrom

Perceptual narrowing in novice divers.

It was hypothesized that in diving, danger-induced stress may contribute to performance decrement by narrowing perceptual scope. A study was conducted to examine the effect of task load and type of underwater exposure on response time to a signal light in the visual periphery. Novice divers monitored a peripheral light alone, or while simultaneously performing a central addition or dial-watching task. Each subject was tested on the surface, in a diving tank, and in the open ocean. It was found that the central tasks did not interfere with peripheral vigilance on the surface. During diving, a distinct subgroup of the dual-task subjects exhibited markedly increased response times to the peripheral light while maintaining near constant performance on the central tasks. Their behavior appeared more closely related to diving risk than to other environmental factors. The remaining dual-task subjects, and the light alone group, were almost uneffected by underwater exposure. The hypothesis was considered partially validated.

Perceptual Narrowing during Simulated Pressure-Chamber Exposure

In this study, 15 male subjects performed a central visual acuity task (Landolt ring detections) and a peripheral light detection task during what they thought to be a 60-ft. dive in a pressure chamber. There was no actual pressure change. A 15-man control group performed the same tasks at an outside location. Experimental measures included a posttest anxiety checklist and continuous heart rate recording. The chamber group showed significantly higher anxiety scores and also a significantly higher heart rate throughout the experiment. There was no difference between the groups with regard to correct Landolt detections, although the chamber group responded somewhat slower. Peripheral detection, however, was severely and significantly degraded in the chamber group. It was concluded that perceptual narrowing had been demonstrated as a result of psychological stress associated with exposure to the “dangerous” pressure-chamber.

Cognitive Efficiency of Divers Working in Cold Water

The cognitive efficiency of 14 divers was studied during 1-hour exposure to water of 40°F (4.4°C) and 78°F (25.6°C). Reasoning ability was tested using a sentence comprehension task presented at the beginning and end of each test session. Vigilance was tested by requiring subjects to detect the onset of a faint peripheral light during the performance of a two-man pipe assembly task. Memory was tested by requiring subjects to learn a number of “facts” during the dive, with retention tested by recall and recognition on land, after a 40-min delay. Despite a mean drop in rectal temperature of 1.3°F (0.72°C), neither reasoning nor vigilance was impaired. Memory performance did deteriorate, though it is suggested that this may reflect a peripheral context-dependent memory effect. It is concluded that a well-motivated subject may be cognitively unimpaired despite a marked drop in deep body temperature.

Effects of Environment and Experience on Underwater Work Performance

Five experienced divers and 15 novice divers completed a complex underwater assembly task and sets of written problems in a water-filled tank and in the ocean. Performance measurements included subtask completion times, problem-solving accuracy, activity analysis, and basic physiological variables. Experienced divers showed essentially unchanged performance between tank and ocean. Novice divers performed slower than the experienced divers in the tank and showed a marked decrement in both assembly time and problem-solving accuracy in the ocean. The results suggest that diving experience improves underwater motor skills rather than work strategy, and that psychological stress was a significant factor even at shallow ocean depths for novices.

Effects of an Emphasis on Conceptualizing Techniques during Early Learning of a Gross Motor Skill

Abstract Six randomly selected groups of 20 male college students with a right hand preference were studied to determine the effects of varying emphasis on conceptualizing and manual practice during the early learning of a novel ballistic gross motor skill. Variance analysis and an examination of learning curves indicated that five conceptualizing and manual practice methods were more effective in changing human performance than was practice limited to taking the three tests which were given to the control group at the beginning, middle, and conclusion of the four-week period. It was also found that alternating periods of emphasis on conceptualizing and manual practice was as effective as successive periods emphasizing manual practice.

Thrust forces in underwater swimming.

Instantaneous and mean static thrust levels were measured for eight underwater swimmers restrained in a submerged force platform. Swimming was examined barefoot and with two types of fins. The main beneficial effect of the fins was to eliminate the substantial negative thrust component associated with barefoot swimming. Higher maximal thrust outputs were achieved with curved fins than with straight-bladed ones. There were also significant differences between barefoot and finned swimming in the relationship of instantaneous thrust to leg position during the kick cycle. Kick rate and foot acceleration were both proportional to thrust output, but the relationship depended on diver size and experience.

Visual fields of the scuba diver.

The restricted visual fields available to SCUBA divers were examined by means of an under-water perimetry apparatus. Measurements were obtained for three standard partial masks (covering only the eyes and nose), one atypical “wrap-round” partial mask, and one full-face mask. Data are presented along with some consideration of the interactions between mask design and visual field, and a brief resumé of procedural variables affecting human factors experimentation underwater.

Acquisition of Throwing Skill Involving Projectiles of Varying Weights

Abstract This investigation was conducted in order to determine if there were differences in the degree to which accuracy in throwing with the nonpreferred hand was developed when practice with projectiles of varying weights was used during the learning period. The effects of transfer of learning from the throwing of a ball of one weight to performance with a ball of another weight was also studied. The result indicated that practice with a light ball was as effective as practice with a heavier ball in developing skill to throw a heavier ball. Practice with the heavier ball when transferred to the lighter ball did not demonstrate a corresponding effect.

Biomechanical Analysis of the U.S. Navy Mark V and Mark XII Diving Systems

This study is one of a series of human factors analyses comparing two U.S. Navy surface-supported hardhat diving systems - the standard Mark V and the prototype Mark XII. The study assessed the range of motion in the two diving systems, using a biomechanical analysis. Fourteen anthropometric measurements were chosen which represented gross body movements used in hardhat diving and likely to be affected most by diving suits. After measuring each movement, comparisons were made with swim suit baselines to determine how much loss of mobility had occurred. The Mark XII was superior to the Mark V overall, both in wet and dry modes.

Personal Autonomy of Scuba Diver Trainees

Abstract An investigation of personal autonomy levels as measured by the Pensacola Z scale was conducted on 147 scuba diving trainees at the University of California at Los Angeles. The study was part of an effort to develop insight into selection and training procedures for reliable underwater workers. Findings revealed that diver trainees described themselves as individualistically as did groups of astronauts and Antarctic scientists, but their Z-scale scores were not significantly different from other campus groups. Further, the Z-scale did not significantly differentiate between successful trainees and dropouts in the course. A weak relationship was found between the Z-scale score and scuba diving performance during pool testing. It was concluded that the qualities measured by the Z-scale test may be more important to the future diving careers of the subjects than to their selection and training.