Language may be subdivided into smaller constituent components bearing autonomous meaning, that is to say words, whereas extralinguistic communication comes about through the use of components that cannot be decomposed into smaller, autonomous units: A smiling face is a smiling face, and not the sum of many small parts each of which is smiling. I shall present brain-imaging evidence in favor of my distinction in section 2.4, after introducing the theoretical concepts in need.
1.1.1. Linguistic communication: Compositional. Linguistic communication may be defined as the communicative use of a system of symbols. This means that language is an entity based on compositionality: Language is built up recursively from separate components that may be joined together (Chomsky 1957). Some linguistic expressions have an atomic structure; that is, they may not be subdivided into smaller, constituent units. Other expressions have a molecular structure; that is, they are composed of smaller constituents that may in their turn be either atomic or molecular. The semantic content of an expression -be it atomic or molecular -depends both on its global structure and on the semantic content of its constituents.
1.1.2. Extralinguistic communication: Associative. Passing on now to extralinguistic communication, this form of communication may be considered the communicative use of a set of symbols. This mode is essentially noncompositional; that is, it consists of parts and not of constituents. Extralinguistic signals are molecular blocks that cannot be decomposed any further, inasmuch as they are equipped with intrinsic, global significance. The parts do not possess atomic meanings into which they may be further subdivided. The pirouette performed by a ballerina is a pirouette performed by the entire body, and not a pirouette that is performed by the left leg plus a pirouette that is performed by the right leg plus the torsion of the trunk and so forth.
Mental states for communication
Human beings possess, at any given time, a series of mental states. These may be both emotional and cognitive, and both of these may be either conscious or unconscious. Here we will deal only with those states that are relevant for an understanding of the process of communication; that is, states that are causally relevant in interactions between humans. I omit some states on the assumption that they do not constitute primitive notions that form part of the process of the production and comprehension of communication acts.