Scalar adjectives and the temporal unfolding of semantic composition: An MEG investigation

A growing body of research implicates the left anterior temporal lobe (LATL) for combinatorial semantic processing. However, magnetoencephalography (MEG) studies have revealed this activity to be timed quite early, at 200-250ms, preceding the most common time window for lexical-semantic effects. What type of semantic composition could the LATL perform at 200-250ms? We hypothesized that the LATL computes an early stage of composition, taking as its input only the most readily available lexical-semantic information. To test this, we varied the context-sensitivity of prenominal adjectives, postulating that only context-insensitive intersective adjectives (e.g., dead, Italian) should compose in an early time window, whereas the composition of context-sensitive scalar adjectives (e.g., fast, large) should be delayed until the interpretation of the subsequent noun is fully determined. Consistent with this, early combinatory effects in left temporal cortex were observed only for intersective adjectives, though in this study the effects were somewhat more posterior than in prior reports. Overall, our results suggest multiple stages of semantic composition, of which the LATL may index the earliest.