Some Linguistic Evidence of Semantic Domain Knowledge
A central thesis of this chapter is that the semantic domains, as structured by conceptual spaces, form an important part of semantic knowledge. In this section I present linguistic evidence that the development of semantic knowledge can appropriately be described as the development of separable semantic domains.
In the analysis of child language data, the establishment of a word in the vocabulary of children is often analyzed for the average frequency of the word’s usage at a certain age. Typically, the frequency of a word’s usage starts at or close to zero, increases rapidly, then levels off once the word is established in the vocabulary. The resulting curve thus has an S shape. I hereafter call the interval during which usage increases rapidly the establishment period for a word.
I can now formulate a general hypothesis concerning semantic domains: If one word from a domain is learned during a certain establishment period, then other (common) words from the same domain tend to be learned during roughly the same period. In order to test this hypothesis, I have analyzed data from the Child Language Data Exchange System (CHILDES) corpus and have used the publicly available web-based ChildFreq application, a highly efficient tool for such investigations. In this chapter I can present only a few examples from my analysis.
For most of the domains discussed in the previous section, words are established during the language spurt that takes place between 12 and 24 months of age. This observation holds in particular for the different regions of the category domain. For example, consider the region of fruits, part of the category domain. Figure 12.2 shows the frequency curves for the names of several of the most common fruits: apple, banana, pear, grape, and orange. These words have an establishment period
Fig. 12.2 The establishment periods for some common fruit words (Reprinted from Gardenfors (2014, p. 67) with permission from MIT Press)
between 12 and 18 months of age. Orange is something of an exception, probably because it is also used within the color domain.
There are some domains for which the words are clearly established later. One such domain is that relating to life and death. Figure 12.3 shows that the establishment of the words live, die, alive, and dead occurs mostly between 30 and 42 months of age.
Another example is the domain relating to knowledge and memory. Figure 12.4 shows the frequency curves for the words believe, remember, forget, and guess. In this case the establishment period occurs between 36 and 54 months of age. Note that these words concern an individual’s relation to facts and thereby relate to the event domain (see the immediately preceding section). Furthermore, the period coincides with the one during which children learn to pass the false-belief tests.
A final example from ChildFreq concerns the levels of intersubjectivity (see the section on Levels of Intersubjectivity, above). It is difficult to find a clear correspondence between these levels and the learning of particular words. However, I have chosen the verb look as an indicator of understanding the attention of others; and the verbs want to and wanna as indicators of understanding desires; going to and gonna as indicators of understanding intentions; and know, think, and believe (the latter
Fig. 12.3 The establishment periods for some words from the “live” domain (Reprinted from Gardenfors (2014, p. 68) with permission from MIT Press)
two combined into one category) as indicators of understanding belief and knowledge (see Fig. 12.5).
Figure 12.5 suggests that the sequence of the establishment periods conforms to the one I proposed in Gardenfors (2008). An analysis of the uses of these words in different contexts is required in order to establish the connection with intersubjectivity more clearly than I have in this chapter. Note that know, think, and believe do not quite follow the usual S shape. Their trajectories may partly be explained by the many idiomatic uses of these words, which make their frequencies increase at a rate more constant than that of other words. Although I can present only a limited number of examples in these pages, it should be clear that my hypothesis on establishment periods is rich in empirically testable predictions. I invite corpus linguists and child development researchers to continue testing it.
Further evidence of the domain called organization of semantic knowledge is the way that metaphors do not come alone. Lakoff and Johnson (1980) convincingly argued that metaphors are organized around schemas such as “argument is war,” “time is a resource,” and “more is up.” I have proposed that a metaphor expresses an
Fig. 12.4 The establishment periods for some words from the “knowledge” domain (Reprinted from Gardenfors (2014, p. 69) with permission from MIT Press)
“identity in topological or geometrical structure between different domains” (Gardenfors, 2000, p. 176). That is, a word that represents a particular structure in one domain can be used as a metaphor to express the same structure in another domain. Once a metaphor has established such a mapping, it can be exploited to provide other metaphors from the same domain.
An example of such a mapping is the designation of certain computer programs as viruses. This metaphor drawing on the biological domain has created a new way of looking at this class of programs. It has suddenly opened up possibilities for expressions like invasive viruses, vaccination programs, and hard-disk disinfection.
-  An alternative to using age as the independent variable is to consider the general linguistic competence of the children, often measured in terms of an utterance’s mean length (number of words).
-  In fact, a word’s usage usually shows a slow decline, in part because the need for any particularword decreases as more words are learned.
-  ChildFreq was developed by Rasmus Baath. It is available at http://childfreq.sumsar.net/
-  It is difficult to identify any expression that corresponds to understanding emotions (empathy),for this capacity develops well before words are learned.