The use of abstract graphemic information in lexical access

Three experiments investigated the nature of the information required for the lexical access of visual words. A four-field masking procedure was used, in which the presentation of consecutive prime and target letter strings was preceded and followed by presentations of a pattern mask. This procedure prevented subjects from identifying, and thus intentionally using, prime information. Experiment I extablished the existence of a semantic priming effect on target identification, demonstrating the lexical access of primes under these conditions. It also showed a word repetition effect independent of letter case. Experiment II tested whether this repetition effect was due to the activation of graphemic or phonemic information. The graphemic and phonemic similarity of primes and targets was varied. No evidence for phonemic priming was found, although a graphemic priming effect, independent of the physical similarity of the stimuli, was obtained. Finally Experiment III demonstrated that, irrespective of whether the prime was a word or a nonword, graphemic priming was equally effective. In both Experiments II and III, however, the word repetition effect was stronger than the graphemic priming effect. It is argued that facilitation from graphemic priming was due to the prime activating a target representation coded for abstract (non-visual) graphemic features, such as letter identities. The extra facilitation from same identity priming was attributed to semantic as well as graphemic activation. The implications of these results for models of word recognition are discussed.     

Separating effects of orthographic similarity and contour summation in the identification of masked letter strings

We separated effects of contour summation and orthographic similarity under masking conditions, by comparing identification with simultaneous and sequentially presented letter strings, which either did or did not overlap spatially. With overlapping simultaneous stimuli, performance was better for strings with similar contours than for strings with the same letters (the orthographic similarity condition). This suggests that contour summation effects were strongest in the condition where stimuli had similar contours. With sequential presentations, performance in the similar contour and the orthographically similar conditions was equated when the stimuli were overlapping. However, effects of contour summation decreased when prime and target letters were spatially displaced, whereas performance in the orthographically similar condition was maintained. We conclude that effects of orthographic similarity can be distinguished from effects of contour summation, under masking conditions.     

Book reviews

Richards, G. (1987). Human evolution: An introduction for the behavioural sciences. London: Routledge & Kegan Paul. Pp. 374. ISBN 0-7102-0326-8. £40.

Roitblat, H. L. (1987). Introduction to comparative cognition. New York: Freeman. Pp. xiv+377. ISBN 0-7167-17784. Hardback £29.95; paperback £17.95.

Pauly, P. J. (1987). Controlling life: Jacques Loeb and the engineering ideal in biology. New York: Oxford University Press. Pp. 252. ISBN 0-19-50424-1. £22.50.