In the case of auditory information, your friend may have been describing many aspects about bicycles, indirectly causing you to picture your typical bicycle in your mind. Your visual receptors were parsing information about the scene around you, but as most of the information matches your schema for walking in a downtown shopping area, it is not flagged to your attention. Yet, a man in a green and white-stripped shirt may catch your attention as it is a rarity. Also your attention may be focused on this man as he is crossing a dangerous street, something not typically done this time of the day. Next I will describe the breakdown of a visual image into its components.
Light rays bounce from objects in the real world through the lens of the eye onto the retina.
The retina is composed of rods and cones which intercept and interpret the light signals in terms of color, position, and intensity of the signal. The first neural network involved in visual processing interprets these pixel values into visual primitives. This neural net has 1 input node for each rod and cone in the retina. The network has several layers of hidden units and outputs visual components called Geons. It is likely that this neural network has two layers of hidden units, thus allowing linear seperability along three dimensions.