Perceptual recognition thresholds for verbal stimuli may be affected by a number of stimulus attributes related to meaning. Familiarity. meaningfulness, and concreteness of words are among the dimensions that have been investigated, although the findings have been reliable only in the case of familiarity. Whether familiarity is defined experimentally or in terms of word frequency counts, familiar words have consistently been found easier to recognize than unfamiliar words (for summaries, see Dember, 1960, andNeisser, 1967). Meaningfulness as defined by production m (Noble, 1952) has been found to be unrelated to tachistoscopic thresholds in some studies (Taylor, 1958; Winnick & Kressel, 1965) whereas others have found m to be effective in visual recognition (Kristofferson, 1957) and in signal-to-noise auditory perception (Spreen, Borkowski, & Benton, 1967). Contrasting evidence in regard to word concreteness likewise indicates facilitative effects of concreteness on visual duration thresholds (Riegel & Riegel, 1961) and on auditory recognition (Spreen et al, 1967) on the one hand, and qo effect on visual thresholds on the other (Taylor, 1958; Winnick & Kressel, 1965).The position adopted in the present study was that familiarity alone should be related to recognition thresholds. This follows from a theoretical analysis of meaning in terms of representational, referential, and associative levels. The first of these refers to the availability of some form of memory representation corresponding to the physical stimulus. Such a representation presumably is a function of frequency of experience with a stimulus pattern, which determines the ease with which the pattern will arouse the stored symbolic representation, thereby affecting the probability of a correct recognition response. The second level, referential meaning, is most obviously interpreted in terms of the availability of a verbal label for a nonverbal stimulus. Such a definition would be relevant to studies concerned with the effect of verbal codability on perceptual recognition of nonverbal stimuli (e.g., Epstein, 1967), but it is not directly relevant in the present study. What is relevant here is the reverse relation, that is, the availability of a nonverbal representation, such as an image, as an associative reaction to the verbal label. Referential meaning in the latter sense can be defined in terms of the latency of image arousal or concreteness of the words (see Paivio, 1969). Associative meaning is a further level that can be defined partly in terms of the availability of other words as associative reactions to the stimulus. Production m obviously represents one possible operational definition of such meaning.According to the present view, only representational meaning should be related to recognition thresholds because only the availability of a symbolic representation that corresponds most directly to the stimulus itself should be relevant for its recognition. Referential and associative meaning refer to higher-order processes aroused by the ...