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Ocular accommodation and cognitive demand: an additional indicator besides pupil size and cardiovascular measures?

Jainta S, Hoormann J, Jaschinski W - J Negat Results Biomed (2008)

Bottom Line: Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects.An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut fuer Arbeitsphysiologie an der Universitaet Dortmund, Ardeystrasse 67, D-44139, Dortmund, Germany. jainta@ifado.de

ABSTRACT

Background: The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows for remote measurement at the human eye. Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects. Cognitive demand was varied by presenting monocularly numbers at a viewing distance of 5 D (20 cm) which had to be read, added or multiplied; further, letters were presented in a "n-back" task.

Results: Cardiovascular parameters and pupil size indicated a change in autonomic balance, while error rates and reaction time confirmed the increased cognitive demand during task processing. An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.

Conclusion: Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies. From a human factors perspective, expected changes of accommodation due to cognitive demand are of minor importance for design specifications - of, for example, complex visual displays.

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Related in: MedlinePlus

Time scheme of experiment 4. The n-back task contained a letter sequence and subjects had to indicate if the letter in the present step "n" was the same as the one before in step "n-1" or "n-2".
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Figure 6: Time scheme of experiment 4. The n-back task contained a letter sequence and subjects had to indicate if the letter in the present step "n" was the same as the one before in step "n-1" or "n-2".

Mentions: Presenting a central target and varying cognitive demand is easily done within an adaptation of the "n-back"-task: a series of characters is presented in random order for 1000 ms (at 600 ms intervals) and the subjects have to indicate whether the letter in the present step n was the same (or not) as the one before in step n-1 (or n-2) [34,35,39] (see Figure 6). By increasing the number of steps backwards, the demand on processes of the short-term memory is increased, indicated by an increase in reaction time and errors. Typically, the reaction time increases mostly by changing the task from n-1 to n-2, whereas the errors continuously increase with n steps backwards [34,35,39]. To our knowledge, the accommodative response to this "n-back" task is not reported elsewhere yet. We started the letter presentation with a short instruction line and three green letters (A or H); then a series of As and Hs was presented for a 160 s period. After each letter a response was given with a button and the reaction time was measured. Mainly, we varied cognitive demand using n-1 and n-2 tasks (N = 20), but had an additional control run with a n-4 task.


Ocular accommodation and cognitive demand: an additional indicator besides pupil size and cardiovascular measures?

Jainta S, Hoormann J, Jaschinski W - J Negat Results Biomed (2008)

Time scheme of experiment 4. The n-back task contained a letter sequence and subjects had to indicate if the letter in the present step "n" was the same as the one before in step "n-1" or "n-2".
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2542343&req=5

Figure 6: Time scheme of experiment 4. The n-back task contained a letter sequence and subjects had to indicate if the letter in the present step "n" was the same as the one before in step "n-1" or "n-2".
Mentions: Presenting a central target and varying cognitive demand is easily done within an adaptation of the "n-back"-task: a series of characters is presented in random order for 1000 ms (at 600 ms intervals) and the subjects have to indicate whether the letter in the present step n was the same (or not) as the one before in step n-1 (or n-2) [34,35,39] (see Figure 6). By increasing the number of steps backwards, the demand on processes of the short-term memory is increased, indicated by an increase in reaction time and errors. Typically, the reaction time increases mostly by changing the task from n-1 to n-2, whereas the errors continuously increase with n steps backwards [34,35,39]. To our knowledge, the accommodative response to this "n-back" task is not reported elsewhere yet. We started the letter presentation with a short instruction line and three green letters (A or H); then a series of As and Hs was presented for a 160 s period. After each letter a response was given with a button and the reaction time was measured. Mainly, we varied cognitive demand using n-1 and n-2 tasks (N = 20), but had an additional control run with a n-4 task.

Bottom Line: Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects.An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut fuer Arbeitsphysiologie an der Universitaet Dortmund, Ardeystrasse 67, D-44139, Dortmund, Germany. jainta@ifado.de

ABSTRACT

Background: The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows for remote measurement at the human eye. Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects. Cognitive demand was varied by presenting monocularly numbers at a viewing distance of 5 D (20 cm) which had to be read, added or multiplied; further, letters were presented in a "n-back" task.

Results: Cardiovascular parameters and pupil size indicated a change in autonomic balance, while error rates and reaction time confirmed the increased cognitive demand during task processing. An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.

Conclusion: Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies. From a human factors perspective, expected changes of accommodation due to cognitive demand are of minor importance for design specifications - of, for example, complex visual displays.

Show MeSH
Related in: MedlinePlus