Genetic and environmental influences on individual differences in printed word recognition

The genetic and environmental etiologies of individual differences in printed word recognition and related skills were explored in 440 identical and fraternal twin pairs between 8 and 18 years of age. A theoretically driven measurement model identified five latent variables: IQ, phoneme awareness, word recognition, phonological decoding, and orthographic coding. Cholesky decomposition models on these five latent constructs revealed the existence of both common and independent genetic effects, as well as non-shared environmental influences. There was evidence for moderate genetic influences common between IQ, phoneme awareness, and word-reading skills, and for stronger IQ-independent genetic influences that were common between phoneme awareness and word-reading skills, particularly phonological decoding. Phonological and orthographic coding skills in word recognition had both significant common and significant independent genetic influences, with implications for "dual-route" and "connectionist" reading models, subtypes of reading disabilities, and the remediation of reading disabilities.     

Letter visibility and word recognition: The optimal viewing position in printed words

It has repeatedly been shown that the time and accuracy of recognizing a word depend strongly on where in the word the eye is fixating. Word-recognition performance is maximal when the eye fixates a region near the word’s center, and decreases to both sides of this “optimal viewing position.” The reason for this phenomenon is assumed to be the strong drop-off of visual acuity: the visibility of letters decreases with increasing eccentricity from fixation location. Consequently, fewer letters can be identified when the beginning or ending of a word is fixated than when its center is fixated. The present study is a test of this visual acuity hypothesis. If the phenomenon is caused by letter visibility, then it should be sensitive to variations of visual conditions in which the letters are presented. By increasing the interletter distances of the word(e.g.,a_t_t_e_m_ p_ t), letter visibility was decreased. As expected from our hypothesis, the viewing-position effect became more exaggerated. An additional experiment showed that destroying word-shape information (e.g., aTtEmPt) decreased overall word-recognition performance but had no influence on the viewingposition effect. Varying the viewing position in words might thus be used as a paradigm, allowing one to separate out the contribution of letter information and supraletter information to word recognition.     

Letter visibility and word recognition: the optimal viewing position in printed words.

It has repeatedly been shown that the time and accuracy of recognizing a word depend strongly on where in the word the eye is fixating. Word-recognition performance is maximal when the eye fixates a region near the word's center, and decreases to both sides of this "optimal viewing position." The reason for this phenomenon is assumed to be the strong drop-off of visual acuity: the visibility of letters decreases with increasing eccentricity from fixation location. Consequently, fewer letters can be identified when the beginning or ending of a word is fixated than when its center is fixated. The present study is a test of this visual acuity hypothesis. If the phenomenon is caused by letter visibility, then it should be sensitive to variations of visual conditions in which the letters are presented. By increasing the interletter distances of the word (e.g., a_t_t_e_m_p_t), letter visibility was decreased. As expected from our hypothesis, the viewing-position effect became more exaggerated. An additional experiment showed that destroying word-shape information (e.g., aTtEmPt) decreased overall word-recognition performance but had no influence on the viewing-position effect. Varying the viewing position in words might thus be used as a paradigm, allowing one to separate out the contribution of letter information and supraletter information to word recognition.     

Interference of spoken word recognition through phonological priming from visual objects and printed words

Three cross-modal priming experiments examined the influence of preexposure to pictures and printed words on the speed of spoken word recognition. Targets for auditory lexical decision were spoken Dutch words and nonwords, presented in isolation (Experiments 1 and 2) or after a short phrase (Experiment 3). Auditory stimuli were preceded by primes, which were pictures (Experiments 1 and 3) or those pictures’ printed names (Experiment 2). Prime–target pairs were phonologically onset related (e.g., pijl–pijn, arrow–pain), were from the same semantic category (e.g., pijl–zwaard, arrow–sword), or were unrelated on both dimensions. Phonological interference and semantic facilitation were observed in all experiments. Priming magnitude was similar for pictures and printed words and did not vary with picture viewing time or number of pictures in the display (either one or four). These effects arose even though participants were not explicitly instructed to name the pictures and where strategic naming would interfere with lexical decision making. This suggests that, by default, processing of related pictures and printed words influences how quickly we recognize spoken words.     

The role of syllabic structure in French visual word recognition

Two experiments are reported in which the processing units involved in the reading of French polysyllabic words are examined. A comparison was made between units following the maximal onset principle (i.e., the spoken syllable) and units following the maximal coda principle (i.e., the basic orthographic syllabic structure [BOSS]). In the first experiment, it took longer to recognize that a syllable was the beginning of a word (e.g., the FOE of FOETUS) than to make the same judgment of a BOSS (e.g., FOET). The fact that a BOSS plus one letter (e.g., FOETU) also took longer to judge than the BOSS indicated that the maximal coda principle applies to the units of processing in French. The second experiment confirmed this, using a lexical decision task with the different units being demarcated on the basis of color. It was concluded that the syllabic structure that is so clearly manifested in the spoken form of French is not involved in visual word recognition.     

Episodic memory reflected in printed word naming

Although memory is typically measured by recall or recognition, it is also expressed by fluent or stylized task performance. In this experiment, 12 volunteers (calledspeakers) completed four experimental stages over a 2-week period. They read printed words aloud in two sessions, before and after exposure to auditory training tokens. They later completed a recognition memory test, discriminating old from new words. Groups ofperceptual judges assessed the speakers vocal imitation by comparing utterances recorded before and after training and deciding which sounded like “better imitations” of the training tokens. The data showed clear evidence of postexposure imitation, with systematic effects that preclude strategic explanations. The contents of episodic memory were reflected by participants speaking style while they were reading aloud. Together, the imitation and recognition data suggest that memory preserves detailed traces of spoken words; those traces were apparently activated when participants later read the same words in the same context.     

Effects of subphonetic and syllable structure variation on word recognition

This study explored whether natural acoustic variations as exemplified by either subphonetic changes or syllable structure changes affect word recognition processes. Subphonetic variations were realized by differences in the voice-onset time (VOT) value of initial voiceless stop consonants, and syllable structure variations were realized by vowel deletion in initial unstressed syllables in multisyllable words. An auditory identity priming paradigm was used to determine whether the amount of facilitation obtained to a target stimulus in a lexical decision task was affected by the presence of these acoustic variations in a prime stimulus. Results revealed different patterns for the two types of variability as a function of lexical status. In the case of subphonetic variations, shortening of VOT resulted in reduced facilitation for words but not for nonwords, whereas in the case of syllable structure variation, vowel deletion in an unstressed syllable resulted in reduced facilitation for nonwords and increased facilitation for words. These findings indicate that subphonetic variability interferes with word recognition, whereas syllable structure variability does not, and that this effect is independent of the magnitude of the acoustic difference between a citation form and its variant. Furthermore, the results suggest that the lexical status of the target item plays a crucial role in the processing of both types of variability. Results are considered in relation to current models of word recognition.     

Visual attention shift to printed words during spoken word recognition in Chinese: The role of phonological information

The aim of this study was to investigate the extent to which phonological information mediates the visual attention shift to printed Chinese words in spoken word recognition by using an eye-movement technique with a printed-word paradigm. In this paradigm, participants are visually presented with four printed words on a computer screen, which include a target word, a phonological competitor, and two distractors. Participants are then required to select the target word using a computer mouse, and the eye movements are recorded. In Experiment 1, phonological information was manipulated at the full-phonological overlap; in Experiment 2, phonological information at the partial-phonological overlap was manipulated; and in Experiment 3, the phonological competitors were manipulated to share either fulloverlap or partial-overlap with targets directly. Results of the three experiments showed that the phonological competitor effects were observed at both the full-phonological overlap and partial-phonological overlap conditions. That is, phonological competitors attracted more fixations than distractors, which suggested that phonological information mediates the visual attention shift during spoken word recognition. More importantly, we found that the mediating role of phonological information varies as a function of the phonological similarity between target words and phonological competitors.     

Phonology in multisyllabic word recognition

The present study used two word-naming experiments to investigate whether a phonological representation is computed in the perception of multisyllabic words. In the first experiment, 100- or 250-msec beginning syllable previews were given, followed by the whole word. The results indicated that no phonological representation was computed at 100 msec, but a phonological representation was computed at 250 msec. In Experiment 2, the second syllable was given as a prime for either 100 or 250 msec. The results showed that no phonological representation was computed for the end of a multisyllabic word. Results are discussed in terms of current dual-route theory and connectionist models.This research was supported by a National Science Foundation grant BNS90110067. We thank Kim Clements, Cindy Connine, Fred Smith, Steve Straight, Sheldon Li, Steve Specht, Greg Boheimer, Deb Briihl, Rich Topoloski, Anna Chomiak and Chris Bruun for their support.     

Parafoveal processing in word recognition

Two experiments investigated the degree to which properties of a word presented in the parafovea influenced the time to process a word undergoing concurrent foveal inspection. In Experiment 1, subjects viewed a set of five-letter words at a fixed point, with words in parafoveal vision varying in length, word frequency, and both the type and token frequency of occurrence of their initial three letters. The results showed that the frequency of the target and the type frequency of its initial letters influenced foveal fixation time. In Experiment 2, subjects executed a sequence of saccades before initial fixation on the experimental items. Under these circumstances, fixation time was shorter overall. Lexical properties of parafoveal words had no effect on foveal processing, but the length and the type frequency of their initial letters exerted a strong influence. Parafoveal-on-foveal effects of this form are incompatible with models of reading in which attention is allocated sequentially to successive words. The data are more consistent with the proposition that foveal and parafoveal processing occurs in parallel, with processing distributed over a region larger than a single word. Subsidiary analyses showed little influence of any of the manipulated variables on saccade extent.     

Parafoveal-on-foveal interactions in word recognition

An experiment is reported in which participants read sequences of five words, looking for items describing articles of clothing. The third and fourth words in critical sequences were defined as "foveal" and "parafoveal" words, respectively. The length and frequency of foveal words and the length, frequency, and initial-letter constraint of parafoveal words were manipulated. Gaze and refixation rate on the foveal word were measured as a function of properties of the parafoveal word. The results show that measured gaze on a given foveal word is systematically modulated by properties of an unfixated parafoveal word. It is suggested that apparent inconsistencies in previous studies of parafoveal-on-foveal effects relate to a failure to control for foveal word length and hence the visibility of parafoveal words. A serial-sequential attention-switching model of eye movement control cannot account for the pattern of obtained effects. The data are also incompatible with various forms of parallel-processing model. They are best accounted for by postulating a process-monitoring mechanism, sensitive to the simultaneous rate of acquisition of information from foveal and parafoveal sources.     

The role of letter recognition in word recognition

In a paradigm that avoids methodological problems of earlier studies, evidence was gathered addressed to the question of whether we read letter by letter. If word recognition involves letter recognition, then the difficulty of recognizing a word should vary with the difficulty of recognizing its letters. This was tested by assessing letter difficulty in two letter discrimination tasks and in a letter naming task, and then comparing 15 adult subjects' visual recognition latency to 72 easy-letter words and to 72 difficult-letter words. Word frequency and word length were also manipulated. Results indicated no effect for letter difficulty, although recognition latency reliably decreased with word frequency and monotonically increased with word length (21 msec/letter), suggesting that we do not read letter by letter, but that whatever plays a role in word recognition is smaller than the word and correlated with word length in letters.     

Familiarity and word recognition

Word recognition was examined for physics and non-physics students after a single visual presentation of a series of sixty words. Physics words likely to be familiar only to physics subjects were used to vary the prior familiarity of the two groups with the inspection material and the ratio of physics to common words (salience) was varied for each of the three inspection series. Common words, which were expected to have greater salience than physics words in one of the inspection series, were not found to be recognized better than the control pairings of physics words by either group of subjects. The absence of differences between physics and non-physics students in the number of inspection list words (positive instances) correctly identified supports the view that prior familiarity is not a critical variable when all inspection items are presented in a recognition test. Physics students made fewer errors than non-physics students in identifying both physics and common words in the the recognition test which were not in an inspection series (negative instances). It is suggested that the correct identification of negative instances involves a scanning of a subject's “internal store” of previously experienced inspection items and that this is more efficient when the meaning of all the items in this “store” is known.     

Age-at-acquisition and word recognition

Recent investigations have shown that the latency in object naming is affected by when in life the naming word is learned—the age-at-acquisition of the naming word. The present study investigated the effect of age-at-acquisition in the recognition of tachistoscopically presented words. It was found that, with word frequency controlled, words judged to be of early acquisition had a significantly lower recognition threshold than words judged to be of later acquisition.     

Models of word recognition

Major hypotheses about the processes involved in word recognition are reviewed and then assessed through four experiments. The purpose of the first experiment was to examine some basic aspects of the processing of words, pseudowords, and nonwords, and beyond that, to discover basic differences in their processing that might underlie the word advantage. The second experiment was designed to assess the contribution of whole-word and letter cluster cues to the word advantage. Finally, Experiments III and IV were focused on the question of whether the word advantage can be wholly explained in terms of response bias or sophisticated guessing. Taken together, the results of these experiments were most compatible with criterion bias models. A version of the criterion bias model is suggested wherein the word advantage is attributed to interfacilitation among single letter and lexical units in memory.