The time course of semantic richness effects in visual word recognition

Abstract

The richness of semantic representations associated with individual words has emerged as an important variable in reading. In the present study we contrasted different measures of semantic richness and explored the time course of their influences during visual word processing as reflected in event-related brain potentials (ERPs). ERPs were recorded while participants performed a lexical decision task on visually presented words and pseudowords. For word stimuli, we orthogonally manipulated two frequently employed measures of semantic richness: the number of semantic features generated in feature-listing tasks and the number of associates based on free association norms. We did not find any influence of the number of associates. In contrast, the number of semantic features modulated ERP amplitudes at central sites starting at about 190 ms, as well as during the later N400 component over centro-parietal regions (300-500 ms). Thus, initial access to semantic representations of single words is fast and word meaning continues to modulate processing later on during reading.

Keywords: ERPs; N400; semantic richness; visual word recognition; word meaning.

Figure 1

Global field power (GFP; n = 24; 62 channels) as a function of lexicality (A), the number of semantic features (B), and the number of associates (C). Vertical lines indicate borders of ERP segmentation, based on measures of global map dissimilarity (GMD; D).

Figure 2

Top. Influences of lexicality and the number of semantic features on event-related brain potentials at posterior electrode sites. Bottom. At left is a map of electrode locations with the depicted sites PO9 and PO10 highlighted in dark gray. To the right is the topographical distribution of the lexicality effect (words minus pseudowords) between 130 and 240 ms.

Figure 3

Influences of the number of semantic features on event-related brain potentials at centro-parietal electrode sites. On the right are topographical distributions of feature effects (many minus few semantic features) between 180 and 240 (top) and between 300 and 500 ms (middle), as well as a map of electrode locations with the depicted sites highlighted in dark gray.