Integration and coarse coding: right hemisphere processing of message-level contextual information

A number of different models have been proposed in order to explain the underlying processing mechanisms of each hemisphere for contextual information in sentences. While the coarse-coding hypothesis (Beeman, 1998) remains prominent in the literature, it is inconsistent in its current form with strong evidence suggesting that the RH has a capacity for comprehension that extends beyond word-level processing. Experiment 1 set out to investigate the proposed special role of the RH for integrating broad concepts by centrally presenting one, two, or three sentences followed by an associated word or nonword target to either the left or right visual field. Each sentence, in itself, provided only minimal cues to the nature of the target, but in combination with others created a much more powerful context. A total of 32 right-handed undergraduate psychology students participated in a computer-based lexical decision task where reaction time and error rates were recorded. In contrast to expectations based on the coarse-coding hypothesis, targets presented to the RVF/LH were as strongly facilitated as targets presented to the LVF/RH at all levels of contextual support. Due to some ambiguity in the results as to the level of processing of each hemisphere, an additional experiment was conducted which aimed to resolve this difficulty through a modification to the scrambled sentence condition. Experiment 2 provided a clear demonstration that the equality of facilitation observed in both experiments occurred as a result of message-level processing. This finding indicates that the coarse/fine-coding distinction between left and right hemisphere processing cannot be applied to message-level processing.