Multiletter Word Units in Visual Recognition: Direct Activation by Supraletter Visual Features

Multiletter priming effects have been interpreted as evidence for the representation of separable multiletter units in the visual word recognition system (Whiteley & Walker, 1994). The reported experiments examine whether the activation of such units is pre- or post-lexical. Experiments 2 and 3 employed priming in an alphabetic decision task in which subjects made a discrimination response to test stimuli which could be classed as either targets or foils. Targets were single letters, or consonant bigrams, present or absent in an immediately preceding word, or (Experiment 3 and 4) they were whole words semantically associated or not to a preceding word. Foils were single non-alphanumeric characters, a character plus a letter, or a word with one letter replaced by a character. Experiment 1 was a preliminary to determine the parameters of a sequential presentation manipulation. Experiment 2 compared conditions of simultaneous and sequential presentation where letters of prime words were presented together, or one at a time in rapid succession. With simultaneous presentation, responses to bigram targets were facilitated when these appeared in the prime word, while responses to individual constituent letters of those bigrams were not facilitated. Additionally, responses to primed bigram targets were faster than responses to primed single letter targets. The sequential presentation of prime words resulted in a qualitative change in the response pattern indicative of the disruption of multiletter unit activation. That change was replicated in Experiment 3 where semantic priming confirmed that the prime words were being processed to a level of meaning. The observations challenge a post-lexical account of the multiletter priming effects. Finally, Experiment 4 addressed the question of whether bigram priming reflects the intentional use of prime information to predict following targets. Strategic interpretations are undermined and it is argued that multiletter units are activated automatically as part of normal visual word recognition.     

Orthographic onsets and rimes as functional units of reading

Three experiments are described in which a partial identity priming procedure was used to investigate the hypothesis that orthographic onsets and rimes serve as units of visual word recognition. In Experiment 1, partial identity priming using word-final trigrams was observed only when the bigram corresponded to the orthographic rime unit. Nonrime primes were again ineffective primes. In Experiment 3, partial identity priming using word-initial bigrams was observed only when the bigram corresponded to the orthographic onset unit. Non-onset bigrams were ineffective primes. These differential priming outcomes cannot be explained by graphemic priming, prime frequency, or practice effects. They are consistent with the hypothesis that syllable onset and rime units serve as functional units of reading.     

Are letter codes always activated?

This investigation assesses whether a word’s constituent-letter codes are activated when whole-word processing is encouraged, as well as when letter processing is encouraged. In Experiments 1 and 2, word primes were followed by a target item that had to be named. The target was a word, a constituent letter that had appeared in the prime, or a nonconstituent letter that had not appeared in the prime. The measure of constituent-letter activation was the difference in letter-naming latency between constituent and nonconstituent letters. Presumably, if constituent letters are named faster, letters are being activated by the words in which they appear. To encourage either whole-word or letter analysis during the processing of the priming word, the proportion of word versus letter targets was systematically varied. When the proportion heavily favored letter targets, constituent letters were named faster than their nonconstituent controls. However, a constituent-letter (vs. a nonconstituent-letter) advantage was not obtained when the proportion favored word targets. Experiment 3 replicated the effect with a priming task that required a discrimination response, instead of a naming response. Thus the results suggested that the activation of constituent-letter codes need not take place during the processing of words, but occurs only when letter analysis is stressed by the task.     

Identity primes produce facilitation in a colour naming task

Five experiments examined associative or identity priming effects in a colour-naming task with colour-neutral words. In Experiment 1, subjects instructed to read the prime silently showed no associative priming effect but a colour-naming facilitation with identity priming. In Experiment 2, the typical associative priming interference in colour naming was demonstrated in subjects recalling the prime word, but not in subjects reading the prime silently, whereas associative primes facilitated word naming regardless of the prime response requirement. The remaining studies investigated the colour-naming facilitation observed with identity primes. Experiment 3 showed no effects on the facilitation of colour naming from varying the letter case of a silently read prime. Experiment 4 showed facilitation when subjects recalled the prime, and a target frequency effect, with faster colour-naming latencies for high- and medium- than low-frequency targets. In Experiment 5, there was no facilitation for naming the colour of target words paired with non-word primes differing in their initial letter from the target. Taken together, the results suggest that the facilitation of colour naming following identical primes reflects faster target word recognition, whereas the associative priming interference reflects an attentional effect.     

Letter transpositions within and across morphemes

Three masked-prime naming experiments were conducted to examine the impact of morpheme boundaries on letter transposition confusability effects. In Experiment 1, the priming effects of primes containing letter transpositions within (sunhsine) and transpositions across (susnhine) the constituents of compound words were compared with correctly spelled primes and primes containing letter substitutions in naming correctly spelled targets. Primes containing transpositions within morphemes facilitated naming as much as correctly spelled primes. Primes with transpositions across morphemes did not facilitate naming more than primes with letter substitutions. Experiment 2 replicated Experiment 1 and extended the effects to so-called pseudocompounds (mayhem). Experiment 3 extended the results to agentive derivational morphology (boaster). The results are discussed in the context of visual word recognition.     

Automatic letter priming in an alphabetic decision task

An alphabetic decision task was used to study effects of form priming on letter recognition at very short prime durations (20 to 80 msec). The task required subjects to decide whether a stimulus was a letter or a nonletter. Experiment 1 showed clear facilitatory effects of primes being either physically or nominally identical to the targets, with a stable advantage for the former. Experiment 2 demonstrated that uppercase letters are classified more rapidly as letters (vs. non-letters) when they are preceded by a briefly exposed, forward- and backward-masked, visually similar uppercase letter than when they are preceded by a visually dissimilar uppercase letter. Finally, Experiment 3 demonstrated that nominally identical and visually similar primes facilitate processing more than do nominally identical, visually dissimilar primes. The alphabetic decision task proved to produce sensitive and stable priming effects at the feature, letter, and response-choice level. The present results on letter-letter priming thus constitute a solid data base against which to evaluate other priming effects, such as word-letter priming. The results are discussed in light of current activation models of letter and word recognition and are compared with data simulated by the interactive activation model (McClelland & Rumelhart, 1981).     

Associative priming in color naming: interference and facilitation

In Experiment 1, color-naming interference for target stimuli following associated primes was greater in a group making a lexical decision to the prime than in a group reading the prime silently. High-frequency targets were responded to more quickly than low-frequency targets. In Experiment 2, with subjects naming the prime, there was evidence of associative interference when the prime and the target were grouped temporally but not when the intertrial interval was comparable with the prime-target interval. Associative primes presented at a short (120-msec) prime-target stimulus onset asynchrony facilitated color naming in Experiment 3. Taken together, the results suggest that the effect of faster processing of the base word in a color-naming task is facilitatory and that color-naming priming interference arises when associative prime processing increases conflict between word and color responses by enhancing phonological or articulatory activation of the base word.     

The relative position priming effect depends on whether letters are vowels or consonants

The relative position priming effect is a type of subset priming in which target word recognition is facilitated as a consequence of priming the word with some of its letters, maintaining their relative position (e.g., csn as a prime for casino). Five experiments were conducted to test whether vowel-only and consonant-only subset primes contribute equally to this effect. Experiment 1 revealed that this subset priming effect emerged when primes were composed exclusively of consonants, compared with vowel-only primes (csn-casino vs. aia-animal). Experiment 2 tested the impact of letter frequency in this asymmetry. Subset priming effects were obtained for both high- and low-frequency consonants but not for vowels, which rules out a letter frequency explanation. Experiment 3 tested the role of phonology and its contribution to the priming effects observed, by decreasing the prime duration. The results showed virtually the same effects as in the previous experiments. Finally, Experiments 4 and 5 explored the influence of repeated letters in the primes on the magnitude of the priming effects obtained for consonant and vowel subset primes (iuo-dibujo and aea-madera vs. mgn-imagen and rtr-frutero). Again, the results confirmed the priming asymmetry. We propose that a functional distinction between consonants and vowels, mainly based on the lexical constraints imposed by each of these types of letters, might provide an explanation for the whole set of results.     

Contextual facilitation in a letter search task depends on how the prime is processed

In a variety of situations it has been observed that the processing of a verbal stimulus is facilitated when it is preceded by an associated word. This article is concerned with determining whether such facilitation occurs automatically upon prime presentation or whether facilitation depends on the manner of processing the prime. Experiment 1 demonstrated that a letter search in a target word was facilitated when the target was preceded by either an identical or semantically associated word. If, however, a letter search was required in the prime as well as in the target (Experiment 2), the relative advantage enjoyed by targets preceded by identical-word primes disappeared. Experiment 3 replicated this loss of facilitation using semantically associated word pairs. Contextual facilitation thus appears to depend upon the mode of analysis of the prime. If the prime is analyzed as a meaningful unit, facilitation occurs. If, however, it is subjected to a more discrete, letter-by-letter analysis, the priming effect vanishes.     

The use of abstract graphemic information in lexical access

Three experiments investigated the nature of the information required for the lexical access of visual words. A four-field masking procedure was used, in which the presentation of consecutive prime and target letter strings was preceded and followed by presentations of a pattern mask. This procedure prevented subjects from identifying, and thus intentionally using, prime information. Experiment I extablished the existence of a semantic priming effect on target identification, demonstrating the lexical access of primes under these conditions. It also showed a word repetition effect independent of letter case. Experiment II tested whether this repetition effect was due to the activation of graphemic or phonemic information. The graphemic and phonemic similarity of primes and targets was varied. No evidence for phonemic priming was found, although a graphemic priming effect, independent of the physical similarity of the stimuli, was obtained. Finally Experiment III demonstrated that, irrespective of whether the prime was a word or a nonword, graphemic priming was equally effective. In both Experiments II and III, however, the word repetition effect was stronger than the graphemic priming effect. It is argued that facilitation from graphemic priming was due to the prime activating a target representation coded for abstract (non-visual) graphemic features, such as letter identities. The extra facilitation from same identity priming was attributed to semantic as well as graphemic activation. The implications of these results for models of word recognition are discussed.     

For a psycholinguistic model of handwriting production: testing the syllable-bigram controversy

This study examined the theoretical controversy on the impact of syllables and bigrams in handwriting production. French children and adults wrote words on a digitizer so that we could collect data on the local, online processing of handwriting production. The words differed in the position of the lowest frequency bigram. In one condition, it coincided with the word's syllable boundary. In the other condition, it was located before the syllable boundary. The results yielded higher movement durations at the position where the low-frequency bigram coincided with the syllable boundary compared to where the low-frequency bigram appeared before the syllable boundary. Syllable-oriented strategies failed with the presence of a very low-frequency bigram within the initial syllable. Further analysis showed that children in grades 3 and 4 privileged syllable-oriented programming strategies. The production times of children in grade 4 were also affected by syllable frequency and, to a lesser extent, bigram frequency. The adults writing durations were modulated by bigram frequency. Therefore, both bigrams and syllables regulate handwriting production although the influence of bigrams was stronger in adults than children. In the light of these results, we propose a psycholinguistic model of handwriting production.     

Graded effects of number of inserted letters in superset priming

Three masked priming experiments investigated the effects of target word length and number of inserted letters on superset priming, where irrelevant letters are added to targets to form prime stimuli (e.g., tanble-table). Effects of one, two, three, and four-letter insertions were measured relative to an unrelated prime condition, the identity prime condition, and a condition where the order of letters of the superset primes was reversed. Superset primes facilitated performance compared with unrelated primes and reversed primes, and the overall pattern showed a small cost of letter insertion that was independent of target word length and that increased linearly as a function of the number of inserted letters. A meta-analysis incorporating data from the present study and two other studies investigating superset priming, showed an average estimated processing cost of 11 ms per letter insertion. Models of letter position coding are examined in the light of this result.     

Masked onset priming effect for high-frequency words: further support for the speech-planning account

Two experiments investigated whether priming due to a match in just the onset between a masked prime and target is found with high-frequency target words. Forster and Davis (1991, Exp. 5) reported that the masked onset priming effect was absent for high-frequency words and used the finding to argue that the effect has its locus in the grapheme-phoneme mapping process that operates serially within the nonlexical route. Experiment 1 used primes that were unrelated to targets and found a masked onset priming effect of equal size for high-frequency and low-frequency target words. Experiment 2 used form-related primes as used by Forster and Davis, and again found that the effect of onset mismatch was not dependent on target word frequency. These results are interpreted in terms of an alternative view that the masked onset priming effect has its origin in the process of preparing a speech response.     

Parts outweigh the whole (word) in unconscious analysis of meaning

In unconscious semantic priming, an unidentifiable visually masked word (the prime) facilitates semantic classification of a following visible related word (the target). Three experiments reported here provide evidence that masked primes are analyzed mainly at the level of word parts, not whole-word meaning. In Experiment 1, masked nonword primes composed of subword fragments of earlier-viewed targets functioned as effective evaluative primes. (For example, after repeated classification of the targets angel and warm , the nonword anrm acted as an evaluatively positive masked prime.) Experiment 2 showed that this part-word processing was potent enough to oppose analysis at the whole-word level. Thus, smile functioned as an evaluatively negative (!) masked prime after repeated classification of smut and bile . Experiment 3 found no priming when masked word primes contained no parts of earlier targets. These results suggest that robust unconscious priming (a) is driven by analysis of part-word information and (b) requires previous classification of visible targets that contain the fragments later serving as primes. Contrary to a widely held view, analysis of subliminal primes appears not to function at the level of analysis of complete words.     

Activation of morphemic meanings in processing opaque words

Two masked priming experiments were conducted to examine the activation of morphemic forms and meanings during opaque word processing. In Experiment 1, opaque primes significantly facilitated the recognition of transparent targets, which was consistent with previous results. However, transparent primes did not influence the recognition of opaque targets. This asymmetry could not be explained solely by morpho-orthographic processing, but it was consistent with models that have assumed early morpho-semantic activation. Experiment 2 directly tested whether the meanings of the constituent morphemes in opaque words were activated. In the critical condition, the targets were unrelated to the opaque primes at the lexical level, but were semantically related to their morphemes (e.g., “butterfly–bread”). Facilitation was observed in this condition, providing strong evidence of morpho-semantic activation during opaque-word recognition. These findings indicate that although initial morphological decomposition is determined by surface morphological form, it does not necessarily imply that morphemic meanings will be activated at later stages of processing. Rather, the morphemic meanings may be available automatically once segmentation is complete.     

On the interaction between linguistic and pictorial systems in the absence of semantic mediation: Evidence from a priming paradigm

Use of the letter search task in the context of the priming paradigm has proved to be an invaluable tool for the investigation of the strategic control of processes involved in word recognition. In particular, previous findings that letter search on a prime word interferes with the priming of semantically/associatively related targets, but not with the priming of either identical or morphologically related targets, suggests that letter search may selectively interfere with semantic processing, leaving other levels of processing intact. In the present experiments, this investigation was extended by exploring the priming of pictures following letter search of either a same-concept word (repetition priming) or a semantically/associatively related word (semantic priming). There was significant repetition priming of picture categorization following both silent reading and letter search of the prime word (Experiments 1 and 2). In contrast, semantic priming of pictures was found only following silent reading of the prime; there was no semantic priming following letter search of the prime (Experiment 2). This pattern of results suggests that focusing attention at the letter level during prime processing selectively attenuates activation of the semantic system by the prime. It does not prevent the spread of activation between the lexical and pictogen levels of representation of a given concept.     

Processing of distractors inside and outside the attentional focus in a priming procedure

A priming procedure was used to study the processing of distractors located either inside (between the location of two targets) or outside (peripherally to the locations of the targets) the focus of attention. The stimuli were five-letter arrays, and participants had to decide whether two marked target letters were the same or different. In Experiments 1 and 2, positive priming was obtained both when targets and in-distractors in primes repeated as targets in probes; negative priming was found when out-distractor primes repeated as targets in probes. In Experiment 3, we also manipulated the match in letter case from primes to probes. In-distractors produced reliable positive priming, irrespective of whether the letters matched in case. In contrast out-distractors produced negative priming but only when the letters had the same case in primes and probes. These results are attributed to a spatial attention process operating (in this case) on low-level visual features, and an object-based selection process that enables more abstract information to be processed for selected stimuli.     

Effects of prime-target spatial separation and attentional deployment on masked repetition priming

In two masked repetition priming experiments with letter stimuli, the positions of prime and target stimuli were varied horizontally from fixation. Priming effects did not interact with position when prime and target location covaried (Experiment 1A) but diminished with increasing prime eccentricity when targets were always centrally located (Experiment 1B). Two accounts of this pattern of priming effects were proposed that postulate two different mechanisms over and above effects of visual acuity. The integration account postulates degree of separation of prime and target stimuli as the critical factor, and the attentional account postulates spatial attention as the critical factor. The results of Experiment 2, in which prime and target positions were manipulated orthogonally, were in favor of the attentional account. Repetition priming did not vary as a function of whether or not primes and targets appeared at the same location, but target processing was facilitated independently of priming when targets appeared at the same location as primes, especially in the right visual field.     

Evidence for word length coding during visual word recognition

In a masked priming procedure manipulating orthographic neighbourhood size, the priming word activates a number of word candidates of which the target could be one. Whether the target is one of the candidates or not determines how quickly it is recognised. However, the efficiency of lexical processing may be markedly less if all possible candidates are activated. One solution to this problem is if the visual system uses prime length information to reduce the number of candidates to a more manageable amount. Here, we investigated in two masked priming experiments whether prime length and orthographic information combine to facilitate target word recognition. In Experiment 1, we showed that the efficiency of visual word recognition is not influenced by the length of primes alone. However, when combined with orthographically related primes, word length coding is preserved. In Experiment 2, we investigated whether length priming affects recognition of short and long words differently. Results showed that only short words benefit from a same-length orthographically related prime, and that the priming effect does not generalise to longer words. These results suggest that the length of a word is not an essential feature in lexical processing, but that it can facilitate recognition by constraining the activation of orthographically related words.     

Retroactive semantic priming in a lexical decision task

The present study reports two experiments that required subjects to name target items preceded by a masked prime. Additionally, and subsequent to the naming task, subjects were required to indicate whether or not the prime was a word, along with a confidence rating of their lexical decision. Experiment 1 demonstrates that the processing of masked primes is facilitated by related targets when such targets are presented either 100 or 200 msec after the onset of the prime. Experiment 2 extends the finding of “retroactive” priming to a 1000=msec separation in prime-target presentation (SOA). The extent of retroactive priming is not dependent on SOA between prime and target, nor is it affected by the prime-mask SOA, which varied from 10 to 180 msec. Priming of targets was also independent of prime-target and prime-mask SOA, providing that primes had been classified as words. For word primes classified as non-words there was no semantic priming on target naming reaction time. Implications of these findings with respect to the nature of retroactive priming and the current controversy concerning subliminal priming effects were discussed.