Academic journal article Canadian Journal of Experimental Psychology

One Missing-Letter Effect: Two Methods of Assessment

Academic journal article Canadian Journal of Experimental Psychology

One Missing-Letter Effect: Two Methods of Assessment

Article excerpt

Abstract When participants search for a target letter while reading, they make more omissions if the target letter is embedded in frequent function words than in less frequent content words. This effect is usually observed with a paper and pencil procedure. It has been shown that a similar pattern is observed vising a rapid serial visual presentation procedure in which words appear one at a time on a computer screen. It has been questioned, however, whether the two methods tap the same cognitive processes. Item-based correlations between the paper and pencil and the rapid serial visual presentation procedure were high and not significantly different from reliability estimates of either procedure. It is concluded that both procedures highlight the same cognitive processes that are responsible for the missing-letter effect.

When readers are asked to circle all instances of a target letter while reading a prose passage for comprehension, they miss more target letters embedded in frequent function words than in less frequent content words (Corcoran, 1966; Healy, 1994; Koriat & Greenberg, 1994). This well-replicated phenomenon, termed the missing-letter effect, has been used to investigate the cognitive processes involved in reading. As of yet, this phenomenon has been intensively studied with a paper and pencil procedure. In an effort to evaluate the major competing theoretical proposals accounting for the missing-letter effect, investigators have begun to study it using different procedures (Haclley & Healy, 1991; Healy, Oliver, & McNamara, 1987; Saint-Aubin & Klein, 2001; Saint-Aubin, Klein, & Roy-Charland, 2003). Among these procedures, the rapid serial visual presentation (RSVP) procedure in which words are presented one at a time at the centre of a computer screen has been found very promising for such nn evaluation.

The RSVP procedure was initially introduced in the field by Healy et al. (1987) to examine the effects of display size on the missing-letter effect. Subsequently, based on RSVP and other findings, the parafoveal processing hypothesis was proposed to account for the influence of eye movements on the missing-letter effect (Hadley & Healy, 1991). The parafoveal processing hypothesis is based on the observation that frequent function words are more likely to be skipped during reading than control content words of the same length (O'Regan, 1979; Saint-Aubin & Klein, 2001). When a word is not fixated, it is assumed to be identified in the parafovea, during fixation of the previous word (see, e.g., Rayner, 1999). Because resolution decreases as the printed material is further away from the fovea, letter identification would be harder for nonfixated words. Because frequent function words are more likely to be skipped during reading, there would be more omissions of their target letter.

In support of this hypothesis, Healy et al. (1987) used an RSVP procedure in which words were presented one at a time at the centre of a computer screen. Because all words are presented at fixation, omission rate should be similar for frequent function words and less frequent content words. Although their results conformed to this prediction, Saint-Aubin and Klein (2001) subsequently showed that this was due to their usage of a too slow presentation rate (between 500 ms and 1,500 ms per word). With presentation durations closer to the usual fixation durations in reading (200, 250, and 350 ms per word), the usual missing-letter effect was found with a variety of target words and in both French and English (Saint-Aubin & Klein, 2001; Saint-Aubin et al., 2003).

Despite the observation of a large missing-letter effect with an RSVP procedure, it could be argued that the missing-letter effect in this procedure is due to different processes. Indeed, there have been some doubts about its validity for distinguishing between explanations of the missing-letter effect. For example, it has been argued that while with a usual paper and pencil procedure, readers are assumed to move on to the next text segment only after completing identification of the word currently in view, with an RSVP procedure, rend ers might be exposed to the next word before completing the identification of the word currently in view. …

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