Visual search in large letter arrays containing words: are words implicitly processed during letter search?
The word superiority effect (Cattell, 1886) is discussed in psychology for more than a century. However, a question remains whether automatic word processing is possible without its spatial segregation. Our previous studies of letter search in large letter arrays containing words without spatial segregation revealed no difference in performance and eye movements when observers searched for letters always embedded in words, never embedded in words, or when there were no words in the array (Falikman, 2014; Falikman, Yazykov, 2015). Yet both the percentage of participants who noticed words during letter search and their subjective reports whether words made search easier or harder significantly differed for target letters within words and target letters out of words. In the current study, we used the Processes Dissociation Procedure (Jacoby, 1991) to investigate whether words are processed implicitly when observers search for letters. Two groups of participants, 40 subjects each, performed 1-minute search for 24 target letters (either Ts, always within words, or Hs, always out of words) in the same letter array of 10 pseudorandom letter strings, 60 letters each, containing 24 Russian mid-frequency nouns. After that, they filled in two identical word-stem completion forms, each containing the same 48 word beginnings (24 for words included in the array). First, the participants were instructed to use words that could appear in the search array ("inclusion test"), then – to avoid using such words ("exclusion test"). Comparison of conscious and unconscious processing probabilities revealed no difference between them (with the former not exceeding 0.09 and the latter not exceeding 0.11), no difference between the two conditions, and no interaction between the factors. This allows concluding that, despite of subjective reports, words embedded in random letter strings are mostly not processed either explicitly or implicitly during letter search, and that automatic unitization requires spatial segregation.