Niedeggen M, Ludowig E, Heil M, Rolke B, Harris C, 2003, "Priming a visual illusion" Perception 32 ECVP Abstract Supplement
Priming a visual illusion
M Niedeggen, E Ludowig, M Heil, B Rolke, C Harris
The perception of an illusory word can be induced by using the technique of rapid serial visual presentation (RSVP). If two consequently presented words share the same string of letters ('CREEP' - 'SHEEP'), a partial repetition blindness is induced, generating a free-floating fragment ('SH'). This fragment is likely to be linked to a second one ('IFT') if both combine to a meaningful word (illusion: 'SHIFT'). The illusory word shares the perceptual quality of 'real' words, and is reported with the same confidence. Using event-related brain potentials (ERPs), we examined whether the illusory word shares the semantic properties of a real word. RSVP streams (10 Hz item-1) containing two meaningful words (W1, W2) and a word fragment (FR) were presented to fourteen subjects. Each trial was preceded by a prime word, was semantically unrelated, or related either to the real word (W2), or the intended illusory word. The probability of naming W2, but not the illusion, was 24% for unrelated, and increased to 42% for related primes. The corresponding probabilities for naming the illusion, but not W2, were 52% and 71%, respectively. A pairwise comparison (unrelated - related) was also applied to extract the ERP correlates of semantic priming. If W2 was named, the effects of priming reflected in a negative-going wave starting at 200 ms, located at frontal leads. A similar negativity characterised the semantic priming effect in the case of a word illusion. However, the onset of the more transient ERP effect was delayed at 500 ms, and it was focused at left-posterior leads. The topographical differences of ERPs indicate that priming of real words facilitates the activation of higher semantic associations, whereas it supports the construction of a visual word form if illusions are triggered.
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