If I describe respiration globally, I must first describe the large meteorological and social movements that in their interaction regulate the quality of the air. Gradually, I arrive at a global description of the physiology of respiration. At the interior of these large movements of the environment and of the organism, the scientist will study some local events. For example, he can study the interaction between the nostrils and the air. This is a local interaction if we think that the nostrils automatically inhale the air that is near the nose. As soon as a local environment is situated in a global mechanism, the question of the organization that relates one global mechanism to a local mechanism becomes relevant.
The notion of module is an example of a local mechanism. A modular mechanism attends to a number of events. When these events occur, it extracts a certain amount of information, treats this information in a standard way, and produces a behavior that varies according to the information received in a standardized way. Here are three domains that illustrate different ways of using the concept of a module.
1. Modules and the neurology of vision.91 The concept of modules was mostly introduced in psychology by the researchers who studied the visual cortex.92 For example, Hubel and Wiesel observed that the stimulation of the retina creates a neurological activity that starts at the eyes and ends up in the visual cortex above the nape of the neck. There, small pillarsâ of neurons extract particular information from this flow of neurological activity and produces distinctions that did not hitherto exist in the brain. Each pillar is a module,93 to the extent that it extracts a certain type of information and deduces a certain number of properties that produce a chemical behavior that correlates with the analyzed data. This behavior is information that will be used to create a perception. Each module will produce, in independent fashion, data on the shape, color, contrasts, degree of mobility, direction of movement, and so on. Not only does each module work independently of the others, in addition, its analysis does not take into account the operations that were previously performed in the brain by other modules.
2. The subroutines of a computer program. We find a similar organization in most computer programs. One program is composed of one or more programs; and each one coordinates a series of subprograms or subroutines that can be used in many different ways by each program. In addition, each subroutine can coordinate many other subroutines. The more we descend in the hierarchy of the organization of a software program, the more the hierarchy becomes fuzzy. A subroutine can activate another subroutine; it can activate or deactivate a program; it can shut down the computer. Some subroutines are used more often than others. Thus, the majority of existing programs contain a series of subroutines that make it possible to save data on an external data storage device (a CD, a USB drive, etc.). Each time a program is used by someone who does not use such a device, this series of subroutines will not be used.
3. Modularity and philosophy. Models on modular brains and machines appeared in U.S. research institutes during the 1960s. One of these was the Massachusetts Institute of Technology (MIT). MIT is one of the centers of artificial intelligence. It created this discipline by recruiting the help of not only engineers but also researchers in other disciplines and philosophers. They set about to elaborate a theoretical model that allowed for the fabrication of machinery, the study of how nature manages modular information, and to find the concepts necessary to create the relationship between the formulations of the engineers and what is observable. The work of U.S. philosopher Jerry Alan Fodor (1983), Modularity of Mind, is often quoted; I suspect that it is mostly due to his title, because the content is focused on the rapport between modularity and theories concerning the localization of the psychic functions in the brain, like phrenology. Somewhat like Kant with regard to Hume, Fodor (1998, 2000) tries to show that modularity is a form of the organization of information that makes it possible to describe relatively simple neurological mechanisms, but that it is improbable that the functioning of human reasoning could be understood with a model of this type.