Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Arguably the most important function of memory is categorization. The rings of a tree or the scratches on a stone can be said to "remember" the past, but human memory can do more: it is capable of using the literal past to build abstractions that are useful to predict the future. It is able to build generalizations. Actually, categorization is the principal way that humans have of making sense of their world. For example, if we analyze the grammar of our language, the basic mechanisms of meaning-bearing are processes of categorization.
One can even wonder whether all living beings, or at least many of them, need to achieve some level of categorization in order to deal with the world.
The German linguist Eric Lenneberg argued that all animals organize the sensory world through a process of categorization. They exhibit propensities for responding to categories of stimuli, not to single specific stimuli. In humans this process of categorization becomes "naming", ie, the ability to assign a name to a category. But even in humans the process of categorization is still a process whose function is to enable “similar” response to “different” stimuli. For example, we “sit” on a “chair”, regardless of how different this chair is from other chairs on which we sat in the past.
Traditionally, categories were conceived as being closed by clear boundaries and defined by common properties of their members. In the 1950s the US psychologist Jerome Bruner proposed that one could conceive of categories as sets of features: a category is defined by the set of features that are individually necessary and jointly sufficient for an object to belong to it. In order words, one can write down the rules that specify what is necessary and sufficient for a member to belong to a category.
This seems to be the case for nominal types (the one invented by us, such as “mother” or “triangle”), but not necessarily for natural types. As the great Austrian philosopher Ludwig Wittgenstein pointed out, a category like "sport" does not fit the classical idea (both cards and chess and football are sports, but they have very little in common). A dog that does not bark or a dog with three legs or a vegetarian dog would probably still be considered a dog, even if it violates the set of features we usually associate with the concept of a dog. What unites a category is "family resemblance", plus sets of positive and negative examples. Its boundaries are not important: they can be extended at any time.
Bruner was among the first to realize that most cognitive processes are nothing but classification processes in disguise. Cognitive activity ("thinking") depends on placing an event or situation in the appropriate category. A category is basically a set of events that can be treated the same way by the cognitive organism. Bruner also realized that categories are not "discovered" but "invented". They do not exist in the environment: they are construed by the human mind. Thus the inferences that matter are really the one that helps create a new category based on some events, and the inference that helps classify an event relative to the existing categories. A concept is a network of such inferences that allow us to infer an event's category based on some observed attributes of the event, and then to infer the unobserved attributes of that event. His "functionalist" definition of an object, for example, is the network of inferences about it that one is capable of employing after an act of categorization. There exist different kinds of concepts that employ and trigger different kinds of inferences A common kind of inference is the one that all members of a category share some common attributes, but this is only one of the possible inferences to define a category.
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