Differential backward masking of words and letters by masks of varying orthographic structure

Abstract

The effects of structural relationships between targets and masks were investigated using a backward-masking paradigm. Specifically, the masking of single letters, common fiveletter words, and five-letter pseudowords masked by a blank flash, strings of overlapped letters, pseudowords, and words was investigated. Target duration was varied from 2 to 32 msec, with mask duration held constant at 25 msec. The dependent measure was the critical interstimulus interval for correct target identification. Letters were more effectively masked than words and pseudowords. A blank mask caused the least amount of masking, followed by the overlapped letter strings, and then the word and pseudoword masks. In addition to the overall greater masking effectiveness for the three patterned masks, overlapped letter strings masked letters more effectively than they did words. The implications of current theories of masking for these results and the implications of these results for theories of word recognition were discussed.In 1969, Reicher demonstrated that for brief visual presentations, letters are recognized more accurately when embedded in four-letter words than when presented alone, even when the redundancy advantage for words is controlled. This advantage for words over letters, or "word-letter effect," was obtained when the letters and words were followed by a visual mask. Johnston and McClelland (1973) demonstrated that the word-letter effect depends on the presence of a pattern mask. They replicated Reicher's word-letter effect with a pattern mask, but found performance equivalent for words and letters when the pattern mask was replaced by a contourless masking field. Juola, Leavitt, and Choe (1974) also found equivalent performance for words and letters in the Reicher task when they used a dark postexposure field. The primary question raised by these findings is why different masks differentially favor the recognition of words and letters.One suggestion as to the source

Word superiority over isolated letters: The neglected case of forward masking

“…However, the finding that such a small duration shift can remove a substantial word advantage does have a precedence, at least for backward-masked displays. Taylor and Chabot (1978) examined the influence of exposure duration on the relative perceptibility of words and isolated letters in backward pattern-masked displays. Stimuli were presented over a range of exposure durations, and their relative perceptibility was determined by the interval between target offset and mask onset that was necessary to achieve a particular performance criterion (accurately reporting four consecutive targets).…”

“…Despite the popular interpretation placed on the findings of earlier research into the effects of pattern masks and blank fields on word-letter performance, this research actually provides only equivocal support for the notion that backward pattern masks are a necessary component of the WLP. Specifically, while Johnston and McClelland (1973), Juola et al (1974), Marchetti and Mewhort (1986), Massaro and Klitzke (1979), and Taylor and Chabot (1978) found that the WLP disappeared when blank fields were used instead of backward pattern masks, these findings were actually obtained using displays in which a blank field both followed and preceded each stimulus. Specifically, while each study used blank poststimulus fields, Juola et al (1974), Marchetti and Mewhort (1986), Massaro and Klitzke (1979), and Taylor and Chabot (1978) preceded each word and isolated letter with a plain dark field, and Johnston and McClelland (1973) used a plain white field for both poststirnulus mask and prestimulus fixation field.…”

“…More specifically, while the word advantage over single letters presented in arrays of meaningless characters (e.g., number signs, #h##; dollar signs, $h$$; ampersands, &h&&) appears to be insensitive to the type of poststimulus field employed (patterned or blank; Johnston & McClelland, 1973;Marchetti & Mewhort, 1986;Mewhort & Johns, 1988), the word advantage over isolated letters (e.g., h ) has so far been observed only when stimuli are followed by pattern masks and disappears when blank poststimulus fields are used (e.g., Johnston & McClelland, 1973;Juola, Leavitt, & Choe, 1974;Marchetti & Mewhort, 1986;Massaro & Klitzke, 1979; see also Taylor & Chabot, 1978). For example, Johnston & McClelland (1973) presented four-letter words (e.g., coin), letters in number signs (c###), and isolated letters (c ) in two backwardmasked conditions.…”

“…One particular finding in this area has maintained a considerable impact on contemporary views of word recognition since it was first reported more than twenty years ago. Using a two-alternative forced-choice procedure (generally known as the ReicherWheeler paradigm), a number of studies have shown that when alphabetic stimuli are followed by a pattern mask (composed of irregular arrangements of letter fragments or similar contours), letters in words are reported more accurately than are the same letters presented in isolation (e.g., Carr, Davidson, & Hawkins, 1978;Carr, Lehmkuhle, Kottas, Astor-Stetson, & Arnold, 1976;Estes, 1975a;Hawkins, Reicher, Rogers, & Peterson, 1976;Holender, 1979;Johnston, 1978Johnston, , 1981Johnston & McClelland, 1973, 1980Jordan & de Bruijn, 1993;Massaro & Klitzke, 1979;Purcell & Stanovich, 1982;Reicher, 1969;Rumelhart & McClelland, 1982;Taylor & Chabot, 1978;Wheeler, 1970). Moreover, this advantage for words appears to be due to the perceptual processing of these items, and not to the use of some form of postperceptual guessing strategy based on orthographic knowledge.…”

On the relations between crowding and visual masking

“…For example, masks consisting of letter segments, letters, or words produce different recognition performances for the same target letters (e.g., Massaro & Cohen, 1994;Taylor & Chabot, 1978;Turvey, 1973). Also, crowding effects depend on the kinds of flankers/masks (Bouma, 1970;Huckauf, Heller, & Nazir, 1999;Styles & Allport, 1986).…”