The Right Hemisphere: An Investigation into Its Roles in New Word Acquisition and Possible Individual Differences

The current project investigated the right hemisphere role in new words and meanings acquisition, and examined whether this is modulated by an individual's reading skill as measured by Nelson-Denny Reading Test. Beeman proposed that the right hemisphere has a coarse coding style, and is better able to integrate weak semantic relations in con-trast to more fine semantic coding within the left hemisphere (Beeman & Chiarello, 1998), A coarse coding style may help in learning the meanings of new words (Ince & Christman, 2002). In addition, a right hemisphere advantage in learning new words may be influenced by reading skill (see Perfetti, Wlotko, & Hart, 2005). The current project also examined quantitative versus qualitative hypotheses for lateralization of word acqui-sition; the former emphasizes the amount of experience with words, while qualitative hy-pothesis emphasizes brain maturation state. Two experiments were included in the cur-rent project. First experiment presented the new words and meanings were presented ei-ther 2 or 8 times, thereby varying the number of semantic learning contexts. Second ex-periment added an English condition. Forced choice recognition tested learning of new words, followed by the critical divided visual field semantic relatedness judgment test. It was predicted that skilled readers would utilize the most appropriate hemispheric strat-egy, resulting in a left hemisphere advantage for more experienced words, and right hemisphere advantage for less experienced words. Less-skilled readers were predicted to have less hemispheric asymmetry in the more experienced condition. The combined ex-periment data suggest an advantage for rvf/LH for English words. The top 25% of com-prehenders had lvf/RH performance that is much more efficient than the bottom 25% of comprehenders. This was not observed when the groups were divided by median split. Experiment 2 data showed English condition had a robust rvf/LH advantage, which was not observed in the 2x and 8x condition. This may be taken to support coarse-fine coding hypotheses. It is concluded that a highly increased experience with words is crucial for rvf/LH advantages to emerge, superior comprehenders have more efficient RH process-ing, and that left-lateralization happens through increased experience with individual words (i.e., the quantitative hypothesis is supported)