XXI. INTERNATIONALER KONGRESS FÜR LUFT -UND RAUMFAHRTMEDIZIN
17.-21. SEPTEMBER 1973 - MÜNCHEN

XXI st INTERNATIONAL CONGRESS OF
AVIATION AND SPACE MEDICINE

XXI e CONGRES INTERNATIONAL DE
MEDICINE AÉRONAUTIQUE ET SPATIALE

Vorabdrucke der Vorträge
Preprints of scientific programma
Préprints des communications scientifiques

OBJECTIVE ASSESSMENT OF MENTAL LOAD DURING FREE ESCAPE FROM A DIVING CABIN.
LAYOUT (Graphical display)

Haylitt Retief

 Laboratory for Ergonomic Psychology of the Organization for Health Research TNO, Zuiderzeeweg 10, Amsterdam, The Netherlands.

Choice making capacity has often been claimed to be a basic operation in human information processing. In this context the term "mental load" is used when an appeal is made on human information handling capacity (1). This load can be systematically varied by changing the pace in a binary choice task. The binary choice task can also be self-paced. In this mode the next stimulus is presented only if the response to the previous one has been made. In the following experiments this mode was used. Fluctuations in performance are supposed to be related with fluctuations in effectiveness of higher cortical functions involved in continuous attention and short term retention. Such fluctuations might be due to cerebral pathology; to unfavorable physical environmental conditions such as temperature and inappropriate breathing mixture or to stressful psychological conditions such as fear and anxiety. This paper treats a preliminary study in which it was investigated if a binary choice task could be used during free escape from a diving cabin on the bottom of a lake (40 ft.) In a previous study its use in less complex submarine conditions has been evaluated (4).

MATERIAL AND METHODS.

The instrument used (Fig.1) is called a binary choice generator (2). This instrument presents random series of oral or visual binary stimuli to which the subject has to respond to by pressing keys or pedals accordingly. Correct responses, errors and omissions are shown on counters. The stimuli being presented at random order prevent the subjects from the possibility of 'anticipation. For each response a choice has to be made between two alternatives. For the undersea experiments the author developed a special long distance stimulus response unit (Fig.2) connected to the binary choice generator by a cable of 150 ft. The unit consists of a flat metal box which can be easily held in one hand. The light on the center line can be of two different intensifies. Two magnets, left and right of the centerline, are used for responding. The left button had to be pressed when the light was at low intensity, the right button had to be pressed when the light was at high intensity. The intensifies vary according to a random program, generated by the BCG.

Additionally a Moseley stripchart recorder was used. The pen was activated by pulses from a special output on the BCG. Low amplitude pulses represent correct responses. High amplitude pulses represent errors. From the same output an electromagnetic storage was made on a Depex cardiomod. This instrument allows low voltage currents to be stored on standard tape recorders, after preamplification and frequency modulation. All apparatus was situated in a boat moored at a buoy above the cabin. The task was self-paced. The next stimulus was presented immediately after a response was made to the previous one. It was emphasized to the subject that he had to work as quickly and accurately as possible. A competitive atmosphere was created. Measurement was in 3 conditions: 1) in cabin sitting relaxed on shaft edge just before free escape (60 seconds); 2) during free escape (variable time); 3) after free escape, floating alongside boat (60 seconds). The S-R unit was held in the left hand in all conditions.

RESULTS

Fig-3 is an illustration of how results appear on the stripchart recorder (chart speed 30cm/min). Four free escape samples are shown between black vertical lines starting at arrow (traces 1-4 only). Conditions 1 and 3 on either side were not fully reproduced here. At top trace S-R unit is held upside down in condition 3, resulting in errors for correct answers and visa versa. Bottom trace (trace 5) is illustrative of chaotic performance and is sh6wn for comparison. This is a novice diver's performance. Regular section is relaxed on land before diving. This is a type of performance which is more or less representative for performance under relaxed conditions in general. After vertical line (with arrow) performance under "relaxed" conditions in cabin is shown. Fig.4 shows average response rate per minute of 4 free escapees in the 3 conditions as described. The deterioration of performance during free escape is evident, being most pronounced in the error score and performance "blocks". Yet it is clear that choice making capacity is still adequately functioning.

DISCUSSION

The feasibility for using the BCG for measuring choice making capacity in complex submarine conditions has been demonstrated. Typical examples of performance deterioration have been shown. It should be mentioned that the experiment was unfortunately executed under severe conditions. The water was 00 , ice formation beginning, visibility was poor. The experiment continued until sunset, the subaquatic scene being dark by that time. In the cabin a thick fog was present. Various cables and wires leading towards the cabin constituted a risk factor. The author conducted the proceedings from inside the cabin and, as senior diver, was responsible for the divers' safety. This was given considerable priority over scientific discipline. The 4 subjects present the most successful registrations.
A considerable number of registrations with other subjects had to be disregarded since to many uncontrolled factors influenced the results.

The fact that the BCG can be used under water, places the submarine situation among a considerable variety of situations were this method is being used. The method of registration and presentation of results offers a considerable advantage, while lit does not require the continuous activity of an observer making notes and the tedious process of working out test results is eliminated. The fact that the entire procedure is automatic increases objectivity to a considerable extend, thus it has the advantage which an objective psychological test has over crude clinical observation without involving the work. A more sophisticated analysis of the subjects performance, for example with regard to response interval times and fluctuations is possible, because the electronic storage allows direct computer analysis (4). Furthermore since registration is automatic and the stimulus response unit can be placed as a considerable distance from the experimenter, situations can be studied which otherwise would not have been accessible for psychological testing. The method has been used with firemen finding their way in dark narrow subterranean corridors, filled with tear-gas and on top of their 100 ft. ladders. It has also been used in aircraft cockpits, both in simulated and actual flight (3,5). Research with the BCG is continued.

Above as the test was conducted in 1973 by Retief, below how it's done in 1997.
Cosmonauts practice underwater for MIR repair.

>Click here to read an special report by Nando.net on the underwater MIR training.

>>Click here to see undersea laboratory and experimental setup at sea bed

>>>Click here to see underwater and experimental setup at lake bed

REFERENCES

1, Kalsbeek, J.W.H. : Standards of Acceptable Load in ATC Tasks. In: Ergonomics,1971,vol,14,no-5, 641-650.
2. Kalsbeek, J.W.H. : On the Measurement of Deterioration in Performance caused by Distraction
Stress. In: Ergonomics,1964,vol.7,no.2, 187-195.
3. Retief, Haylitt : Variations in ATC-Workload as a Function of Variations in Cockpit. Workload. In: Ergonomics,1971,vol.14,no-5, 585-590.
4. Retief, Haylitt : An Electronic Measurement System for Mental Load in the Submarine Environment. In: Proceedings of the First. Annual. Scientific Meeting of the European Undersea Biomedical Society; Försvars-medicin, Stockholm.
5. Retief, Haylitt, C.H.J.M. Opmeer, : Towards an Objective Assessment of Cockpit Workload: II. The Objective Scoring of Flight Performance, combined with the Introduction of a Distraction Task during the Approach. In: Aerospace Med. in press.

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