The effects of prime visibility on ERP measures of masked priming

Abstract

In two experiments, the effect of the duration (40, 80 and 120 ms) of pattern masked prime words on subsequent target word processing was measured using event-related potentials. In Experiment 1, target words were either repetitions of the prior masked prime (car-CAR) or were another unrelated word (job-CAR). In Experiment 2, primes and targets were either semantically related (cap-HAT) or were unrelated (car-HAT). Unrelated target words produced larger N400s than did repeated (Exp 1) or semantically related (Exp 2) words across the different prime durations and these N400 priming effects tended to be smaller overall for semantic than repetition priming. Moreover, there was only a modest decline in the size of N400 repetition priming at the shortest prime durations, and there was no relationship between this N400 effect and a measure of prime categorization performance. However, the size of semantic priming at the shortest durations was relatively smaller than at longer durations and was correlated with prime categorization performance. The findings are discussed in the context of the functional significance of the N400 as well as a model that argues for different mechanisms during masked repetition and semantic priming.

ERP Evidence of Morphological Analysis from Orthography: A Masked Priming Study

“…It is difficult to know how to interpret this limited difference, although one possibility is that it arose from variations in the visibility of the primes over trials or subjects (cf. Holcomb et al, 2005). Such variations could have allowed limited semantic processing, a possibility not inconsistent with the somewhat reduced (though not reliably so) magnitude of RT priming in the opaque pairs relative to the transparent pairs.…”

“…In attempting such a demonstration, we followed Rastle et al (2004) by comparing the magnitude of masked priming effects in three experimental conditions: transparent morphological (e.g., cleaner-CLEAN ), nonmorphological form (e.g., brothel-BROTH), and opaque morphological (e.g., corner-CORN ). As in other ERP studies (Holcomb et al, 2005;Dominguez et al, 2004;Barber et al, 2002), our principal measure of neural priming was the degree of attenuation in the N400 component of the ERP in response to the targets preceded by the related primes as compared to those preceded by the unrelated primes. We also investigated the onset of the ERP differences elicited by our priming manipulation by examining the earlier part of the ERP segment.…”

“…Behavioral effects were consistent with other long SOA visual priming studies (e.g., Rastle et al, 2000): Robust priming effects emerged only for the semantically related morphological pairs. However, intriguing effects were found in the N400 component of the ERP waveform, previously shown to be sensitive to lexico-semantic information (e.g., Holcomb, Reder, Misra, & Grainger, 2005;Kiefer, 2002;Kutas & Federmeier, 2000). Specifically, Dominguez et al (2004) and Barber et al (2002) found that in the early part of the N400 temporal window, both morphologically related pairs and stem homograph pairs were associated with an attenuated N400 relative to the N400 elicited by unrelated words ( pavo-META, turkey-goal).…”

“…However, this study may also have more general implications in respect of recent controversy regarding the form of processing reflected by N400. Specifically, showing that N400 can be influenced by the morpho-orthographic structure of a consciously imperceptible stimulus would add to the increasing body of evidence disputing Brown and Hagoort's (1993) assertion that N400 reflects conscious, postlexical integration processes alone (e.g., Holcomb et al, 2005;Kiefer, 2002;Deacon, Hewitt, Yang, & Nagata, 2000). This demonstration would instead suggest that N400 can be sensitive to the unconscious, automatic processes characterizing the earliest stages of visual word perception, and which are engaged in the activation of stored orthographic knowledge (see also Holcomb et al, 2005).…”

“…Other claims of unconscious semantic processing have been based on priming experiments that use associates (e.g., Marcel, 1983); priming effects between genuine category coordinates are much more difficult to find, unless primes are classified in visible form prior to subliminal presentation (e.g., Draine & Greenwald, 1998). In the rare cases in which genuine semantic priming effects that do not involve prior conscious manipulation of the prime have been observed (e.g., Perea & Gotor, 1997), prime exposure durations have usually been in the range of partial visibility (67 msec), and could thus be explained through conscious processing of some proportion of the trials (see also Holcomb et al, 2005). To our knowledge, there is no evidence for genuine semantic priming effects on lexical decision under the strict presentation conditions in which this form of morphological decomposition has been observed.…”