Читать книгу The Handbook of Speech Perception - Группа авторов - Страница 53

Despite the difficulty of comprehending the totality of what an example of speech might mean to your brain, there are some relatively easy places to begin. One kind of meaning a word might have, for instance, will relate to the ways in which you experience that word. Take the word ‘strawberry.’ Part of the meaning of this word is the shape and vibrant color of strawberries that you have seen. Another is how it smells and feels in your mouth when you eat it. To a first approximation, we can think of the meaning of the word ‘strawberry’ as the set of associated images, colors, smells, tastes, and other sensations that it can evoke. This is a very useful operational definition of “meaning” because it is to an extent possible to decode brain responses in sensory and motor areas and test whether these areas are indeed activated by words in the ways that we might expect, given the word’s meanings. To take a concrete example of how this approach can be used to distinguish the meaning of two words, consider the words ‘kick’ and ‘lick’: they differ by only one phoneme, /k/ versus /l/. Semantically, however, the words differ substantially, including, for example, by the part of the body that they are associated with: the foot for ‘kick’ and the tongue for ‘lick.’ Since, as we know, the sensorimotor cortex contains a map of the body, the so‐called homunculus (Penfield & Boldrey, 1937), with the foot and tongue areas at opposite ends, the embodied view of meaning would predict that hearing the word ‘kick’ should activate the foot area, which is located near the very top of the head, along the central sulcus on the medial surface of the brain, whereas the word ‘lick’ should active the tongue area, on the lateral surface almost all the way down the central sulcus to the Sylvian fissure. And indeed, these predictions have been verified now over a series of experiments (Pulvermüller, 2005): when you hear a word like ‘kick’ or ‘lick,’ not only does your brain represent the sounds of these words through the progression of acoustic, phonetic, and phonological representations in a hierarchy of auditory‐processing centers that has been discussed in this chapter, but your brain also represents the meaning of these words across a network of associations that certainly engage your sensory and motor cortices, and, as we shall see, many other cortical regions too.

The result of ‘kick’ and ‘lick’ is of fundamental importance because it gives us a leg up, so to speak, on the very difficult problem of trying to understand the representation of semantics in the brain. Of course, not all words are grounded in embodied semantics in the same way. For example, some words are abstract. Consider the word ‘society.’ Questions like “What does a society taste like?” or even “What does a society look like?” are difficult to answer, because societies are not the kinds of things that we taste or see. Societies are not like strawberries. But even abstract words like ‘society’ may contain embodied semantics that become apparent when we consider the ways in which metaphors link abstract concepts with concretely experienced objects (Lakoff & Johnson, 1980). One feature of societies, we might assert, is that they have insides and outsides. In this respect, they are like a great many objects that we experience directly: cups, bowls and rooms. Therefore, it may be hypothesized that even abstract words such as ‘society’ could have predictable effects on the sensorimotor system. Brain areas such as the insula that respond to the physical disgust of fetid smells also respond to the social disgust of seeing an appalled look on someone else’s face (Wicker et al., 2003). There are limits, however, to the embodied view of meaning. Function words such as conjunctions and prepositions are more difficult to associate with concrete experiences. As we have described it, the approach is also limited to finding meaning in the sensorimotor systems, which is unsatisfying as it ignores large swathes of the brain. In the next subsection, we turn to a more ambitious, if abstract, way of mapping the meaning of words that is not limited to finding meaning in the sensorimotor systems.