RESPONSE INSTRUCTIONS AND THE SPEED OF RELATIVE JUDGEMENTS.

It is hypothesized that the speed with which a relative judgement is made between two stimuli on any given dimension depends upon the relation between the general position of the stimuli on the dimension and the direction of the required judgement along this. Experiments involving the discrimination of light patches of different luminance are reported which support this hypothesis. They show that subjects are quicker at choosing the brighter than the darker of two relatively intense stimuli but quicker at choosing the darker of two relatively dark stimuli. A provisional explanation of the phenomenon in terms of a response competition theory of choice behaviour is offered. Some alternative hypotheses are considered and analogies are made with other psychological phenomena. It is concluded that this is a judgemental phenomenon of some considerable generality. [ABSTRACT FROM AUTHOR]