An interactive activation model of context effects in letter perception: Part 2. The contextual enhancement effect and some tests and extensions of the model.

The interactive activation model of cor. text effects in letter perception is reviewed, elaborated, and tested. According to the model context aids the perception of target letters as they are processed in the perceptual system. The implication that the duration and timing of the context in which a letter occurs should greatly influence the perceptibility of the target is confirmed by a series of experiments demonstrating that early or enhanced presentations of word and pronounceablepseudoword contexts greatly increase the perceptibility of target letters. Also according to the model, letters in strings that share several letters with words should be equally perceptible whether they are orthographically regular and pronounceable (SLET) or irregular (SLNT) and should be much more perceptible than letters in contexts that share few letters with any word (XLQJ ). This prediction is tested and confirmed. The basic results of all the experiments are accounted for, with some modification of parameters, although there are some discrepancies in detail. Several recent findings that seem to challenge the model are considered and a number of extensions are proposed.