Different levels of word knowledge in the cerebral hemispheres

Two priming experiments were conducted to investigate if words at the known, frontier, and unknown levels of word knowledge reflect differences in the kind and/or strength of their underlying semantic representations. It was hypothesized that known word knowledge reflects acquired categorical and thematic knowledge, whereas frontier and unknown words reflect acquired thematic representations. It was also hypothesized that these word levels reflect a continuum of meaning acquisition in that as word knowledge increases from unknown to frontier and known levels of knowledge, there would be a corresponding increase in strength of the semantic representations. Both experiments entailed central presentations of known, frontier, and unknown word primes. The targets were also centrally presented in experiment 1, but were laterally presented in experiment 2. The results of experiment I suggest that the kind of semantic representations of known, frontier, and unknown words differ in the predicted manner. The only indication of a change in strength of the semantic representations was between frontier and unknown words. Experiment 2 further investigated the possibility of a lateral shift in processing dominance from the right hemisphere to the left hemisphere as word knowledge increases from the frontier to the known level. This was not fully supported. Rather, it appears as though the findings from experiment 1 were largely mediated by the right hemisphere. The combined results of these two experiments are discussed in terms of a right hemisphere role in acquisition of word knowledge and modulation of metacontrol.