Task demands determine RT retinal location function.

With 3 types of tasks RTs at 7 retinal locations were measured. These tasks were called CRT in which the subjects responded with one of the two keys according to whether the presented digits were odd or even, simple-but-watch condition in which they tried to see clearly the presented digit and then respond in the simple RT manner, and simple-and-quick condition in which they simply responded to the onset of the stimuli. As may be expected, in the latter condition the subjects produced retinal-location function curve which showed only a little degradation at the peripheral positions, while in the CRT condition they responded to the peripheral stimuli much more slowly than to the central ones. The RTs of the simple-but-watch condition fell in between; most subjects showed the responses much like the ones in the simple-and-quick condition, but some of them produced a retinal location function identical in shape (although reduced by approximately 250 msec.) to the one obtained in the CRT condition. This was interpreted to be a failure (for most of the subjects) to direct attention to those parts of the stimulus properties that conveyed information on pattern. These findings gave warning as to the uncritical adoption of a simple-RT paradigm to measure iconic duration.