Why 'looking' helps you 'see'

Common experience tells us that events portrayed on a cinema screen appear to flow smoothly in space and time. However, in reality we are experiencing a very rapid succession of discrete images that are projected at around 25 frames per second. The reason that images appear so smooth to us is because of the nature of our visual system, which creates an illusion of visual continuity. We have evolved this ability because humans make very frequent eye movements called saccades, which move our direction of gaze about three times per second towards interesting targets in the visual scene - a process known as active vision. These saccades cause an endless succession of images in our perception that need to be merged into a single picture.

Intrigued by such integration of rapid-fire images into visual perception, Associate Professor Michael Ibbotson and his colleagues from the Visual Sciences group began a systematic study of the visual brain in behaving animals..Working with primates, and tracking the responses of neurons activated by visual stimuli, they formed the exciting and original conclusion that saccades alter the way in which vision is processed. Visual sensitivity is reduced prior to the onset of a saccade and stays low during the execution of the eye movement; but immediately following a saccade, visual sensitivity is greatly enhanced. In effect, eye movements improve the efficiency of our visual system by adjusting processing capacity during and between saccades. As a result, neural activity in the visual pathway peaks when saccades are frequent.

These recent discoveries confirm the close interplay between the motor system that drives our eye movements, and the visual system with which we perceive our world. Using those highly-differentiated brain structures, we gather information from widely spaced sources then consider particular elements in fine detail, combining peripheral survey with a capacity to focus intensely on central items of interest. The detection of such items increases saccadic activity, so that ‘looking' helps us to ‘see'.

Further Info Online:

• http://www.rsbs.anu.edu.au/Profiles/Michael_Ibbotson