Effect of letter orientation and sequential redundancy on the speed of letter search

Subjects searched for target letters through upright or inverted sentences, words, and nonwords. Letters were easier to detect in sentences (vs. words) and words (vs. nonwords) under less demanding search conditions (e.g., one or two target letters in memory set, upright presentation). Familiar letter orientation aided search under all conditions and its aid did not vary with memory set size (intercept effect only). The latter result, taken together with previous findings, indicates a general familiarity effect at the encoding stage. An analysis of facultative and disruptive sequential redundancy effects indicated that facilitation depends on several key factors and, most important, on having words presented in uppercase.