Semantic priming: on the role of awareness in visual word recognition in the absence of an expectancy

By hypothesis, awareness is involved in the modulation of feedback from semantics to the lexical level in the visual word recognition system. When subjects are aware of the fact that there are many related prime-target pairs in a semantic priming experiment, this knowledge is used to configure the system to feed activation back from semantics to the lexical level so as to facilitate processing. When subjects are unaware of this fact, the default set is maintained in which activation is not fed back from semantics to the lexical level so as to conserve limited resources. Qualitative differences in the pattern of data from two lexical decision experiments that employ masked priming are consistent with this hypothesis. Semantic context and stimulus quality interact when the prime is processed with awareness whereas these same two factors produce additive effects on RT when the prime is unlikely to have been processed with awareness. These experiments thus illustrate one way in which awareness (or lack thereof) affects the dynamics of visual word recognition.     

Word-fragment cuing: the lexical search hypothesis

In four experiments we evaluated aspects of the hypothesis that word-fragment completion depends on the results of lexical but not semantic search. Experiment 1 showed that the number of meaningful associates linked to a studied word does not affect its recovery when the test cue consists of letters and spaces for missing letters. Experiments 2 and 3 showed retroactive interference effects in fragment completion when words in a second list were lexically related to words in a first list but not when the words in the second list were meaningfully related. Experiment 4 indicated that for studied words, instructions to search at the word level facilitated completion performance and that instructions to generate letters to fill missing spaces had no effect. Other findings indicated that completion was affected by the number of words lexically related to the fragment and by the number of letters missing from the fragment. In general, experimental manipulations that focused on lexical characteristics were effective, and those that focused on semantic characteristics were ineffective. The findings support the conclusion that word fragments engender a lexical search process that does not depend on retrieving encoded meaning.     

Contrasting effects of age of acquisition in lexical decision and letter detection

Two experiments studied attention in beginning and skilled readers of Dutch to letter information in function words and content words. Early and late acquired nouns and function words were presented to third-grade students and skilled adolescent readers. Target words were presented in short story contexts, as in the study of Greenberg, Koriat, and Vellutino (1998). Target nouns were matched on word frequency. Predictions of the structural account hypothesis of letter detection (Koriat, Greenberg, & Goldshmid, 1991) were confirmed. No age-of-acquisition effect was found. In contrast, a separately conducted lexical decision experiment using the same content word stimulus sets showed shorter decision latencies for early acquired words. The combined results suggest that during silent reading, when attention is focused on meaning, phonological processes may play a less prominent role than in lexical decision tasks that demand explicit control of phonological codes. The letter detection results confirmed predictions of the structural account hypothesis for both beginning and skilled readers. Taken together, these studies demonstrate that phonological processes in silent reading may play a less prominent role and that the structural account of letter processing is valid for languages other than Hebrew and English but probably is not the unique mechanism involved in letter detection.     

Phonological information in immediate and delayed sentence recall

Potter and Lombardi (1990) state in their conceptual regeneration hypothesis that immediate sentence recall is only based on conceptual and lexical information; phonological information does not contribute. As experimental evidence for this hypothesis, they reported that if a sentence is followed by a word list that included a lure word similar to one of the content words of the sentence (target word), the lure word frequently intrudes into sentence recall. We demonstrated that Potter and Lombardi did not observe any influence of phonological information because list presentation followed sentence presentation, and phonological information was discarded. We observed that phonological information influenced the intrusion rate if recall was not delayed by the subsequent presentation of a word list. With immediate recall, the lure intrusion effect disappeared in auditorily presented sentences. This shows that, if available, phonological information contributes to sentence recall.     

Sequential dependencies in the lexical decision task

Two experiments addressed whether response latency in a trial of the lexical decision task is independent of the lexical status of the item presented in the previous trial. In Exp. 1, it was found that both word and nonword responses were significantly slower when the previous trial had involved a nonword than when it had involved a word. In Exp. 2, which employed a different list composition, it was found that responses to nonwords and pseudohomophones were significantly slower when the previous trial had involved a nonword or a pseudohomophone than when it had involved a word. However, responses to words were not influenced by the nature of the previous trial. We concluded that sequential dependencies exist across consecutive trials in the lexical decision task even when there is no semantic, morphological, phonological, or orthographic relationship between the items presented during those trials.     

How does interhemispheric communication in visual word recognition work? Deciding between early and late integration accounts of the split fovea theory

It has recently been shown that interhemispheric communication is needed for the processing of foveally presented words. In this study, we examine whether the integration of information happens at an early stage, before word recognition proper starts, or whether the integration is part of the recognition process itself. Two lexical decision experiments are reported in which words were presented at different fixation positions. In Experiment 1, a masked form priming task was used with primes that had two adjacent letters transposed. The results showed that although the fixation position had a substantial influence on the transposed letter priming effect, the priming was not smaller when the transposed letters were sent to different hemispheres than when they were projected to the same hemisphere. In Experiment 2, stimuli were presented that either had high frequency hemifield competitors or could be identified unambiguously on the basis of the information in one hemifield. Again, the lexical decision times did not vary as a function of hemifield competitors. These results are consistent with the early integration account, as presented in the SERIOL model of visual word recognition.     

Priming the rules of spelling

This paper reports three spelling experiments that examined the effect of lexical priming through intervening items. In the first and second experiments, a strong effect of word priming on nonword spelling was found, even when two intervening filler items separated prime-target pairs. In addition, the absolute size of the effect was similar when one intervening item separated prime-target pairs and when two intervening items separated prime-target pairs. A much larger effect was found when no intervening items were used, however. This effect did not appear to be related to filler type, as Experiment 1 used nonword fillers, and Experiment 2 used word fillers. The third experiment examined the same effect with two intervening filler items, but instead used nonwords as primes (and thus examined a subsyllabic repetition effect). A similar-sized effect as that of the first and second experiments was found. The most plausible explanation of these results, which is consistent with the interactive dual-route model of spelling, is that they reflect the priming of sound-spelling rules that people use to spell nonwords.     

Recognition of affixed words and the word frequency effect

Three experiments are reported in which the word frequency effect is used as a diagnostic for determining whether affixed words coming from the same stem are stored together or separately in the lexicon. Prefixed words are examined in the first experiment, inflected words in the second and third. In the first two experiments, two types of word are compared where the words in each condition are matched on surface or presented frequency but are varied on the frequency of their stems or base frequency. It is found that lexical decision times are influenced by base frequency, thus indicating that words related by affixation are stored together in the lexicon. The third experiment, however, demonstrates that when base frequency is held constant and surface frequency is varied, lexical decision times are influenced by surface frequency. The results are accounted for by a model of word recognition whereby frequency has its effect at two different stages of the recognition process.     

How to say "no" to a nonword: a leaky competing accumulator model of lexical decision

We describe a leaky competing accumulator (LCA) model of the lexical decision task that can be used as a response/decision module for any computational model of word recognition. The LCA model uses evidence for a word, operationalized as some measure of lexical activity, as input to the YES decision node. Input to the NO decision node is simply a constant value minus evidence for a word. In this way, evidence for a nonword is a function of time from stimulus onset (as in standard deadline models) modulated by lexical activity via the competitive dynamics of the LCA. We propose a simple mechanism for determining the value of this constant online during the first trials of a lexical decision experiment, such that the model can rapidly optimize speed and accuracy in discriminating words from nonwords. Further optimization is achieved via trial-by-trial adjustments in response criteria as a function of task demands and list context. We show that the LCA model can simulate mean response times and response distributions for correct and incorrect YES and NO decisions for a number of benchmark experiments that have been shown to be fatal for deadline models of lexical decision. Finally, using lexical activity calculated by a computational model of word recognition as input to the LCA decision module, we provide the first item-level simulation of both word and nonword responses in a large-scale database.     

Lexical processing and text integration of function and content words: Evidence from priming and eye fixations

The results of two experiments comparing processing of function words and content words are reported. In Experiment 1, priming was present for both related function and related content word pairs, as measured in lexical decision response times. In Experiment 2, participants' eye movements were monitored as they read sentences containing either a high- or a low-frequency function or content target word. Average word length and word frequency were matched across the function and content word conditions. Function words showed frequency effects in first-fixation and gaze duration that were similar to those seen for content words. Clear differences in on-line processing of function and content words emerged in later processing measures. These differences were reflected in reading patterns and reading time measures. There was inflated processing time in the phrase immediately following a low-frequency function word, and participants made more regressions to the target word in this condition than in the other three conditions. The priming effects in lexical decision and the word frequency effects in initial processing measures in silent reading for both word types were taken as evidence of common lexical processing for function and content words. The observed differences in later processing measures in the eye-movement data were taken as evidence of differences in the role that the two word types have in sentence processing beyond the lexical level.     

A word’s meaning affects the decision in lexical decision

The influence of an isolated word’s meaning on lexical decision reaction time (RT) was demonstrated through four experiments. Subjects in two experiments made lexical decision judgments, those in a third experiment pronounced the words used in the lexical decision task, and those in a fourth experiment quickly pronounced their first associative response to the words. Differences in lexical access time for the words were measured with the pronunciation task, and differences in meaning were assessed with the association task. Multiple regression analyses of lexical decision RT were conducted using associative RT, pronunciation RT, and other target word properties (printed frequency, length, instance dominance, and number of dictionary meanings) as predictor variables. These analyses revealed a relationship between lexical decision RT and associative RT after the effects of other variables had been partialed out. In addition, word frequency continued to have a significant relationship to lexical decision RT beyond that shared with pronunciation RT and the other variables. The results of these experiments indicate that at least some of the effect of word meaning and word frequency in lexical decision is attributable to a decision stage following lexical access.     

Automatic processes in lexical access and spreading activation.

The semantic priming effect can be reduced or eliminated depending on how the prime word is processed. The experiments reported here investigate this prime task effect. Two experiments used identity and semantic priming tasks to determine whether the prime word is encoded at a lexical level under letter-search conditions. When the prime task was naming, both identity and semantic priming occurred; however, when a letter-search task was performed on the prime word, only identity priming occurred, thus supporting the argument that the search task affects activation of semantic associates rather than lexical access of the prime word. Another experiment demonstrated that this identity priming was the result of lexical processes rather than of letter-by-letter priming. A cross-modal priming technique demonstrated that the letter-search prime task does not actively suppress activation of semantic associates. The implications of these results for automaticity and for proposed mechanisms of priming are discussed.     

Lexical access and the spelling-to-sound regularity effect

A number of investigators have reported that words that follow spelling-to-sound rules can be recognized faster than words that violate such rules (the “regularity” effect). On occasion, the absence of a regularity effect is reported, however. The first two experiments of the present paper report that a regularity effect can be obtained in a lexical decision task with word sets that previously have been reported not to produce such an effect, when consideration is given to the consistency or inconsistency of the pronunciations of each word’s visually similar ‘neighbors” Subsequent experiments demonstrated that the obtained regularity effect does not vary as a function of mixed- vs. single-case presentation (Experiment 3) or visual quality (Experiment 4) in a lexical decision task. These results are explained in terms of Glushko’s (1979) activation and synthesis model of lexical access. It is argued that the obtained results are incompatible with traditional dual process models of lexical access (which incorporate separate visual and phonological pathways and spelling-to-sound rules) and fully compatible with Glushko’s model. It is concluded that spelling-to-sound regularity is not a property of a word in isolation, but rather a property of a word in the context of visually similar words that are activated in the course of recognition.     

A transfer analysis of the repetition effect in the lexical and ambiguity decision tasks

Two experiments were performed in an attempt to evaluate explanations of repetition priming-the facilitation observed when the same word is processed a second time in the same task. One task employed was lexical decision (word/nonword) and the other was ambiguity decision (ambiguous/ unambiguous). In the first experiment, transfer on a lexical decision task was measured following either a lexical decision or an ambiguity decision. When the identical lists were processed in the first phase for lexical and ambiguity decision, equal repetition effects were obtained on lexical decision. However, when the ambiguity task was presented without nonwords, no repetition priming occurred. In a second experiment, the within-task repetition effect was large for the ambiguity decision, whereas no transfer was obtained from lexical decision to ambiguity decision. The results were interpreted as being consistent with a transfer-appropriate processing account of repetition priming.     

Does the proportion of associatively related pairs modulate the associative priming effect at very brief stimulus-onset asynchronies?

A number of experiments have shown that the magnitude of the associative priming effect increases substantially when there is a high proportion of associatively related pairs in the list when the stimulus-onset asynchrony (SOA) between prime and target is long (more than 400 ms). In the present series of experiments we manipulated the proportion of associatively related pairs when the SOA was very brief (less than 200 ms). If processing of a target word is facilitated automatically by the prior presentation of a related prime, the occurrence of priming should be unaffected by the proportion of related pairs in the list. Experiment 1 showed a robust relatedness proportion effect obtained in a double lexical decision task. Experiments 2-4 used the masked priming technique at several very short SOAs (66, 116, and 166 ms) in lexical decision and naming. The results showed a reliable associative priming effect in the two tasks, which did not differ as a function of the proportion of related pairs. Finally, Experiment 5 used unmasked primes at an 83-ms SOA in which the primes remained in view after the target presentation. As in Experiments 2-4, the associative effect was not modulated by the proportion of associatively related pairs. The implications of these results are discussed.     

Slowed lexical access in nonfluent aphasia: a case study.

A list priming paradigm (LPP) was used to examine the hypothesis that nonfluent aphasics are literally slowed down in automatic access to lexical information. In this paradigm, words are presented visually, and the subject's task is to make a lexical decision on each word as quickly as possible after its presentation. As soon as a lexical decision is made on one word, that word is removed and, after a predetermined interword interval, the next word is presented. In this way, a continuous "list" effect is obtained. Prior studies with both college-age and elderly subjects using the LPP have shown that, independently of age, on the LPP, priming obtains at interword delays of 500 to 800 msec, but not at either shorter or longer interword delays. In the study reported here, the LPP was used to examine delays at which priming obtained for LD, a nonfluent aphasic with a lesion primarily in the left frontal region. Examining interword delays ranging from 500 to 1800 msec, the subject showed priming only at a delay of 1500 msec, a considerably longer delay than that at which neurologically intact subjects have shown priming. Based on these results, it is argued that while automatic access is retained, that access is much slower in a nonfluent aphasic than in neurologically intact elderly subjects. These results are discussed in terms of how slowed lexical access might impact on discourse comprehension.     

Identifying the speech codes

Models of speech processing typically assume that speech is represented by a succession of codes. In this paper we argue for the psychological validity of a prelexical (phonetic) code and for a postlexical (phonological) code. Whereas phonetic codes are computed directly from an analysis of input acoustic information, phonological codes are derived from information made available subsequent to the perception of higher order (word) units. The results of four experiments described here indicate that listeners can gain access to, or identify, entities at both of these levels. In these studies listeners were presented with sentences and were asked to respond when a particular word-initial target phoneme was detected (phoneme monitoring). In the first three experiments speed of lexical access was manipulated by varying the lexical status (word/nonword) or frequency (high/low) of a word in the critical sentences. Reaction times (RTs) to target phonemes were unaffected by these variables when the target phoneme was on the manipulated word. On the other hand, RTs were substantially affected when the target-bearing word was immediately after the manipulated word. These studies demonstrate that listeners can respond to the prelexical phonetic code. Experiment IV manipulated the transitional probability (high/low) of the target-bearing word and the comprehension test administered to subjects. The results suggest that listeners are more likely to respond to the postlexical phonological code when contextual constraints are present. The comprehension tests did not appear to affect the code to which listeners responded. A “Dual Code” hypothesis is presented to account for the reported findings. According to this hypothesis, listeners can respond to either the phonetic or the phonological code, and various factors (e.g., contextual constraints, memory load, clarity of the input speech signal) influence in predictable ways the code that will be responded to. The Dual Code hypothesis is also used to account for and integrate data gathered with other experimental tasks and to make predictions about the outcome of further studies.     

Lexical access of function versus content words

There has been a simmering debate as to whether evidence exists for differential processes of lexical access for function and content words. This has centered around the frequency effect (higher word frequency reducing access times for content words but not function words). Previous work has used the lexical decision paradigm, which has been shown to reflect more than lexical access times. We measured naming times for words in sentences read for meaning. Our findings confirm that lexical access for function words is indeed faster than for content words as predicted by neurolinguistic theory and electrophysiological evidence, but that this difference can be attributed to word predictability (Cloze value) and word familiarity (log frequency). We also show that differences in frequency effect for the two word types holds only for the lower frequency words and not at all for the higher frequency words. We discuss the implications of the results for neurolinguistic theory.     

The influence of word function in the missing-letter effect: Further evidence from French

When asked to detect target letters while reading continuous text, subjects miss more letters in highly common function words than in less common content words. This is known as themissing-letter effect. According to the structural account, the higher omission rates for frequent function words are attributable to their role in supporting the extraction of phrase structure, after which they become lost in the transition from structure to meaning. This implies that word function in and of itself should affect letter detection accuracy. This issue was examined in four experiments while controlling for a number of confounded factors associated with another influential model: the unitization account. The first experiment extended the missing-letter effect to the French language. The second showed that letter detection is influenced by slight variations in the function assumed by the same word, such as when it is used as a definite article as opposed to a pronoun. This effect was observed even when the frequency of the orthographic pattern and the syllable stress patterns were controlled. In the last two experiments, a control was added for another factor: frequency of word meaning. The results indicate that word function contributes to the missing-letter effect over and above what is contributed by frequency of word meaning.