Visual field asymmetries in attention and learning.

It has been suggested that attentional resolution is greater in the lower than in the upper visual field. As there is no corresponding asymmetry between the areas in the primary visual cortex where the input from upper and lower visual fields is processed, an 'attentional filter' has been proposed to act in one or more higher visual cortical areas in order to constrict the availability of visual information to the level of awareness. To investigate this, a visual search array was presented to the entire visual field and reaction times from upper and lower visual fields compared. In a second experiment, subjects were trained in detecting targets in different visual fields. There was no significant difference between reaction times for targets presented in either upper or lower visual fields when the array was presented to the entire visual field. However, when the array was restricted to either the upper or lower visual fields, reaction times were significantly slower for detection in the upper visual field.