The saying, ``A little healthy competition can be a good thing,'' is as true for the brain as it is for other domains like economics and evolution. In the brain, competition between neurons leads to the selection of certain representations to become more strongly active, while others are weakened or suppressed (e.g., in the context of bootstrapping as described above). In analogy with the evolutionary process, the ``survival of the fittest'' idea is an important force in shaping both learning and processing to encourage neurons to be better adapted to particular situations, tasks, environments, and so on. Although some have argued that this kind of competition provides a sufficient basis for learning in the brain [EdelmanEdelman1987Edelman87], we find that it is just one of a number of important mechanisms. Biologically, there are extensive circuits of inhibitory interneurons that provide the mechanism for competition in the areas of the brain most central to cognition.
Cognitively, competition is evident in the phenomenon of attention, which has been most closely associated with perceptual processing, but is clearly evident in all aspects of cognition. The phenomenon of covert spatial attention, as demonstrated by the Posner task [PosnerPosner1980Posner80] is a good example. Here, one's attention is drawn to a particular region of visual space by a cue (e.g., a little blinking bar on a computer screen), and then another stimulus (the target) is presented shortly thereafter. The target appears either near the cue or in the opposite region of space, and the subject must respond (e.g., by pressing a key on the computer) whenever they detect the onset of the target stimulus. The target is detected significantly faster in the cued location, and significantly slower in the noncued location, relative to a baseline of target detection without any cues at all. Thus, the processing of the cue competes with target detection when they are in different locations, and facilitates it when they are in the same location. All of this happens faster than one can move one's eyes, so there must be some kind of internal (``covert'') attention being deployed as a result of processing the cue stimulus. We will see in section 8.5 that these results, and several other related ones, can be accounted for by a simple model that has competition between neurons (as mediated by the inhibitory interneurons).