ABSTRACT
A typical visual scene is filled with a variety of perceptual objects that could lead to a variety of responses on the part of an observer. For example, if one's goal is to avoid a collision with the bike crossing the path ahead, the important information to be extracted from the visual scene is the distance of the bike (i.e., its depth) and its velocity. Properties such as the color of the bike and the identity of the rider may be of less importance to the immediate goal of avoiding collision. However, if one has agreed to meet a friend at a certain time and location, and that friend generally travels by bike, then the color of and the identity of the rider of any bike in the general location become more important. Certain perceptual judgments, such as determining the location and velocity of objects, may be carried out quickly and rather automatically by the visual system; that is, certain perceptual judgments seem to occur whether or not the observer is attending to them. Other judgments, such as determining the identity of objects, may not be automatic but may require the concentration of attention to perform.
