How is knowledge about word meaning represented in the mental lexicon? Current computational models infer word meanings from lexical co-occurrence patterns. They learn to represent words as vectors in a multidimensional space, wherein words that are used in more similar linguistic contexts—that is, are more semantically related—are located closer together.
However, whereas inter-word proximity captures only overall relatedness, human judgements are highly context dependent. For example, dolphins and alligators are similar in size but differ in danger.
Here, we use a domain-general method to extract context-dependent relationships from word embeddings [GloVe]: ‘semantic projection’ of word-vectors onto lines that represent features such as size (the line connecting the words ‘small’ and ‘big’) or danger (‘safe’ to ‘dangerous’), analogous to ‘mental scales’. This method recovers human judgements across various object categories and properties.
Thus, the geometry of word embeddings explicitly represents a wealth of context-dependent world knowledge.
Figure 2: Semantic projection predicts human judgements: sample cases. (a) Examples of 3 features for the same category (animals). Notice that the items—for instance, dolphin versus tiger—change their similarities to one another depending on context (feature), and semantic projection recovers these cross-feature differences. In other words, the model does not recover the same relationships across features. (b) Examples of 3 categories for the same feature (danger). Sample items are highlighted in red for illustrative purposes. For descriptive and inferential statistics, see Table 1: Each panel is based on data from n = 25 participants.