A joint aim of cognitive psychology and neuropsychology has been the decomposition of mental function-the isolation and characterization of basic processes underlying behavior. By convention, the principal techniques used to identify such processes are based on functional dissociation-the observation of selective effects of variables on tasks. Yet, despite their widespread use, the inferential logic associated with these techniques is flawed in two ways. First, it is possible to posit single processes that mimic both single and double dissociation; and second, observation and interpretation of both kinds of dissociation are limited by an assumption of selective influence that most, if not all, psychologists would now reject as false. The aims of this article are twofold: (a) to review and make explicit the inferential limits of single and double dissociation; and (b) to introduce a new technique that overcomes these limits. Called reversed association, this new technique is denned as any nonmonotonic relation between two tasks of interest. We argue that reversed association, in place of functional dissociation, offers a sounder basis for inferring the number of functionally independent processes underlying performance and, having fewer assumptions, offers researchers greater scope for discovering such processes and determining their nature and effects. This research was funded by a grant from the Australian Research Grants Scheme.We wish to thank Max Coltheart and Alistair Mees for their helpful comments on an early draft of this article.

Although it is generally believed that the representational characteristics of verbal stimuli (typescript or speaker's voice, for example) persist for a very brief time in sensory memory, some recent studies suggest that such characteristics may persist much longer. The present experiments show that words are recognized faster and more accurately when they are re-presented in the same voice. This same-voice facilitation did not decline over a 2-min lag. Further experiments showed that subjects could recall the voice in which a word had been presented with 65–75% accuracy after 2 min and 31 intervening items. It is concluded that, in some circumstances, the physical features of verbal stimuli persist in memory for several minutes.

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Two experiments were conducted to determine the functional status of cognates. Two hypotheses were considered. According to the first hypothesis, language is a critical feature governing lexical organization, and cognates may therefore be equated with morphologically unrelated translations. According to a second hypothesis, however, language is not a critical feature governing lexical organization. Instead, the boundaries between perceptual categories are determined by morphological considerations, and cognates may therefore be equated with intra-lingual variations such as inflections and derivations. If the first hypothesis is correct, cognate performance should follow that observed for translations, but if the second hypothesis is correct, cognate performance should follow that observed for inflections and derivations. The experiments used different procedures in order to discount taskspecific explanations. The first experiment involved repetition priming in a lexical decision task, and emphasis was placed on relative priming; that is, on the amount of facilitation which occurs when, for example, OBEDIENCIA primes OBEDIENCE, expressed as a fraction of the amount of facilitation that occurs when the same word is presented on each occasion (i.e., when OBEDIENCE is used to prime OBEDIENCE). The second experiment tested memory for language. Four types of cognates were tested. These were: orthographically identical cognates, regular cognates with cion/tion substitution, regular cognates with dad/ty substitution, and irregularly derived cognates. The results were unequivocal. The priming values observed previously for cognates were qualitatively and quantitatively similar to those observed for inflections and derivations, and this classification was confirmed in the second experiment, involving memory for language. The results are consistent with the general proposition that morphology rather than language governs the boundaries between perceptual categories, and a number of specific explanations are reviewed.

Eight experiments were conducted to resolve: (1) empirical inconsistencies in repetition effects under intermodality conditions in word identification and lexical decision, and (2) an associated theoretical conflict concerning lexical organization. The results demonstrated that although more facilitation occurs under visual-prime!visual-test (VV) conditions than under auditory-prime/visual-test (AVI conditions, significant repetition facilitation also occurs under AV conditions. The results also indicated that: repetition effects observed for the VV and AV conditions apply to high-as well as to low-frequency words; they are insensitive to a variety of encoding tasks designed to emphasize different properties of words; and they are unaffected by differences in the ease of encoding of isolated auditory and visual words. The results are consistent with the existence of both modality-specific and common or modality-free processes in word recognition, in which word-frequency effects are restricted to the second and, by implication, lexical stage.Research into modality differences has focused on a variety of empirical issues over the last 2 decades. For much of this time, interest has focused on episodic questions concerning, for example, the distinctions among sensory, short-term, and long-term memory systems. At the heart of this problem, however, is the modal specificity of the system responsible for the transition from sensory to categorical representation. If categorical information emanates from a single lexicon, albeit via distinct access routines, it follows that equivalent item information will be available following auditory and visual presentation. In this case, then, modality information must be stored dependently, as an associate of the item information. But if distinct lexical systems are involved in reading and in speech recognition, the item information available following auditory and visual presentation may not be equivalent. In this case, modality information may be provided automatically by the item information.Research into the modal specificity of lexical processes has not yielded a definitive answer. One approach to the question involves observation of repetition effects in word-processing tasks. When equivalent repetition effects are observed under inter-and intramodality conditions, it is assumed that a common system is involved. But when the repetition effects are restricted to intramodality conditions, it is assumed that separate mechanisms are involved in text and speech recognition. sented in Morton's (1979) results and is reflected in his model. Using word recognition, with threshold-estimation procedures in vision and audition, he found no evidence of transfer under intermodality conditions. The model that he subsequently developed includes modality-specific word recognition units, or "logogens." According to Morton, these units are not connected except through a separate cognitive system, so intermodality transfer is absent in tasks that tap only word identification processes. Any task...

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An experiment was designed to investigate the locus of persistence of information about presentation modality for verbal stimuli. Twenty-four Ss were presented with a continuous series of 672 letter sequences for word/nonword categorization. The sequences were divided equally between words and nonwords, and each item was presented twice in the series, either in the same or in a different modality. Repetition facilitation, the advantage resulting from a second presentation, was greatest in the intramodality conditions for both words (+ve responses) and nonwords (-ve responses). Facilitation in these conditions declined from 170 msec at Lag 0 (4 sec) to approximately 40 msec at Lag 63. Facilitation was reduced in the cross-modality condition for words and was absent from the cross-modality condition for nonwords. The modality-specific component of the repetition effect found in the word/nonword categorization paradigm may be attributed to persistence in the nonlexical, as distinct from lexical, component of the word categorization process.A number of recent experiments (Hintzman, Block, & Inskeep, 1972;Kirsner, 1973;Craik & Kirsner, 1974) have shown that memory for the physical properties of verbal stimuli-features such as the modality of presentation, the case of visually presented letters, the sex of the speaker of auditorially presented words-lasts for a period too long to be accounted for in terms of echoic or iconic storage (Neisser, 1967). This experiment was concerned with examining how one of these physical features, namely, modality of presentation, is maintained in memory.One possibility is that the effect is a by-product of activation of the lexicon, the permanent memory system which translates stimulus events into the verbal code. If there exist separate auditory and visual lexica, then during the period that activation of a particular lexical unit persists, information about the modality of the stimulus event would be available. Once the encoding was completed and the activation had ceased, this information would be lost. A second possibility is that there is a single lexicon which is involved in encoding all verbal stimuli, regardless of modality of presentation, and that the retention of modality information resides with a different memory component which is not involved in semantic analysis.To differentiate between these two possibilities, a modification of a word identification paradigm introduced by Rubenstein, Lewis, and Rubenstein (197 I) was employed. Ss were exposed to a long series of letter sequences, half of which were common English words. The task was to classify each sequence as to whether or not it was an English word. In this experiment, each item in the continuous series was presented a second time after one of four possible intervals. Reaction time was measured, and the dependent variable was the decrease in the amount of time required to decide whether the sequence was a word when the stimulus was presented for the second time. Pilot work had indicated that such a repetition effe...

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