Bihemispheric visual reaction tasks

The number of alternative stimuli plus the number of alternative responses and the reaction times are strongly related. But the exact relation is questionable. The law of Hick postulates a logarithmic fit and has dominated the discussion. The question arises whether new data fit Hick s law or some other law. Five subjects with nearly 10,000 measurements were used to answer this question. A linear relation was found between reaction time and the number of alternatives when the number of alternatives is not too high. With more alternatives, the relationship is clearly non-linear. 

In a discrimation task, one has to decide which stimulus of a set of stimuli is present and which key of a set of keys is to be pressed in response of this stimulus. The coordination of the stimuli to the keys is given by an instruction before the task begins. The subject has therefore only to decide, which stimulus is present and which key is to be pressed in each single trial. 

The Pathways of Mind Springer-Verlag/Wien 2001 

One can ask whether the logarithmic fit is the adequate function or only an elegant mathematical approximation to a more complex reality. The only way to answer this question is to make new and more measurements of reaction times in tasks with changing number of stimuli and response alternatives. 

Poppel stimulated the start of this work with his observation that a visual reaction task with 2 lamps and 2 keys produced on average a 70 ms longer reaction time that the llamp-lkey- task, the 21amps-lkey-task needed a 50 ms longer reaction time and the 31amps-3keys-task needed 105 ms longer than the llamp-lkey-task. If one takes the llamp-lkey-task as the reference task, the plus of the other times can be computed by this formula  

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A first mathematical theory of bihemispheric visual reaction tasks... 

Table 7. Comparison of the directly observed cycle times in the tasks v221 and v22r in healthy subjects. vCT is the bihemispheric visual reaction time i.e. the slope of the linear regression. A small letter behind the initials means repetition of the tasks...

Fig. 2. Bihemispheric visual median reaction times of the tasks vl 1 to vlOlO of subject PI5 with regression line (broken line). The task vll has a non linear position relative to the...

Fig. 15. Bihemispheric visual median finger reaction times of subject PI2 in the tasks v22...

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