The interfering effect of word perception on letter identification

Subjects identified a single lowercase letter in a visual display by pressing one of two buttons. Two letters were assigned to each response. Groups received one of three context conditions: word, nonword, or single-letter displays. In words and nonwords, the flanking letters adjacent to the target varied as to whether they were response compatible or incompatible with the target. Single letters produced faster response latencies than either multi-letter condition, and words yielded slower latencies than did nonwords. Items Containing an incompatible-response flanking letter produced longer latencies than items containing a compatible flanking letter. Subgroups of subjects with different characteristic processing patterns were identified with a separate test. These subgroups were differentially affected by the context conditions in the letter-identification task. A greater subgroup difference was found in nonwords than in words.     

Effects of increased letter spacing on word identification and eye guidance during reading

The effect of increasing the space between the letters in words on eye movements during reading was investigated under various word-spacing conditions. Participants read sentences that included a high- or low-frequency target word, letters were displayed normally or with an additional space between adjacent letters, and one, two, or three spaces were present between each word. The spacing manipulations were found to modulate the effect of word frequency on the number and duration of fixations on target words, indicating, more specifically, that letter spacing affected actual word identification under various word-spacing conditions. In addition, whereas initial fixations landed at the preferred viewing position (i.e., to the left of a word’s center) for sentences presented normally, landing positions were nearer the beginnings of words when letter spacing was increased, and even nearer the beginnings of words when word boundary information was lacking. Findings are discussed in terms of the influence of textual spacing on eye movement control.     

Forced serial processing of words and letter strings: A reexamination

Words and nonword strings, three and seven letters long, were displayed serially (i.e., one letter at a time) or simultaneously, with or without a backward mask following display of each letter or string. Recognition of words, and of individual letters within words, was markedly impaired in the masked serial condition relative to the unmasked serial, unmasked simultaneous, and masked simultaneous conditions. Analogous differences were smaller or nonexistent for seven-letter nonwords; however, three-letter nonwords produced relatively “wordlike” data. Implications for the issue of spatially serial vs. parallel processing in word recognition are discussed.     

Detection of intraword and interword letter repetition: A test of the word unitization hypothesis

Do words, as familiar units or gestalts, tend to swallow up and conceal their letter components (Pillsbury, 1897)? Letters typically are detected faster and more accurately in words than in nonwords (i.e., scrambled collections of letters), and in more frequent words than in less frequent words. However, a word advantage at encoding, where the representation of the string is formed, might compensate for, and thus mask, a word disadvantage at decoding and comparison, where the component letters of the representation are accessed and compared with the target letter. To better reveal any such word disadvantage, a task was used in this study that increased the amount of letter processing. Subjects judged whether a letter was repeated within a six-letter word or a nonword (Experiment 1; intraword letter repetition) or was repeated between two adjacent unrelated six-letter words or nonwords (Experiment 2; interword letter repetition). Contrary to Pillsbury's word unitization hypothesis, both types of letter repetition (intraword and interword) were detected faster and just as accurately with words as with nonwords. In Experiment 2, however, interword letter repetition was detected less accurately on common words (but not on rare words or third-order pseudowords) than on the corresponding nonwords. Thus, although the familiar word does not deny access to its own component letters, it does make their comparison with letters from other words more difficult.     

Left hemisphere superiority for pronounceable nonwords,but not for unpronounceable letter strings

Right-handed adults were asked to identify bilaterally presented linguistic stimuli under three experimental conditions. In Condition A, stimuli were three-letter pronounceable nonwords (such as TUP), and subjects were asked to report them by naming them. In Condition B, stimuli were three-letter pronounceable nonwords, and subjects were asked to report them as strings of letters. In Condition C, stimuli were more or less unpronounceable letter strings (such as UTP) created by rearranging the letters of pronounceable nonwords, and subjects reported them as strings of letters. Pronounceable nonwords were found to be better identified from the right visual hemifield irrespective of the way in which they were reported. Unpronounceable letter strings did not produce any visual hemifield difference. Nonwords are of interest because they can be seen as potential words that lack both specific semantic properties and entries in the subject's internal lexicon. The results of the experiment are consistent with the view that both the left and right cerebral hemispheres are able to identify letters but the left hemisphere is more sensitive to the pronounceability of the nonwords. This may happen either because the left hemisphere can make better use of resemblances to real words or because it has access to spelling to sound correspondence rules.     

On time differences in searching for letters in words and nonwords: Do they emerge during the initial encoding or the subsequent scan?

Krueger (1970a, 1970b, 1982) has demonstrated that subjects can search for target letters within words faster than they can complete an equivalent search through nonwords, and he further demonstrated that the effect did not arise during the comparison stage. The present study involved three experiments in which the usual word advantage disappeared either when subjects knew where within a display the target item would appear (i.e., it was always the first letter), or when all the component letters were encoded into memory before the task began (i.e., a memory-search task). These data, in conjunction with Krueger's, where interpreted as localizing at least one (and possibly the only) source of the word-nonword difference in this task to the events that occur during the item-to-item transitions subjects make when scanning the letter arrays. That is, these transitions are faster for words than nonwords, and it was suggested that the time difference may emerge because although all the letters from within a word appear to be available in memory before the scan begins, this seems not to be true for consonant arrays. Given that this is the case, part of the word-nonword difference may be attributable to subsequent encoding events that would be needed for the consonant arrays as the scan moves from letter to letter.     

A perceptual-confusion account of the WSE in the target search paradigm

Subjects were required to search through four-letter displays for one member from the target set M, N, P, or R. The displays were words, pseudowords, or consonant strings. The results show that significant word superiority effects occur when target location is unknown, but that a location precue can eliminate these benefits of lexical context. Analysis of the types of errors that occur with and without a location precue indicates that the precue reduces the likelihood that the context letters of nonwords will be confused with the incorrect targets. These findings are consistent with a perceptual-confusion model that predicts that the context letters of words will be perceived more accurately than those of nonwords.     

Letter search through words and nonwords: The effect of fixed,absent, or mutilated targets

The present study attempted to eliminate the word superiority effect found in letter search by holding the target letter fixed across trials. The expectation was that the target would thereby become so familiar and salient that the subject would "see" only that letter during search. Even with the target-letter held fixed (Experiment I), however, search was still faster through words than through nonwords, indicating that nontarget letters had been "seen" as well. Search also remained faster through words than through nonwords when the number of exposures to the target was further increased by having the subject search for the absence rather than the presence of the target letter (Experiment III). In line with the notion of "proofreader's errors," however, search became relatively more accurate on nonwords than on words when it required detection of the "mutilation" produced by substituting an F for an E, e.g., BASKFT, BAKFRY (Experiment IV).     

Visual search through words and nonwords in horizontal and vertical orientations.

In a repeated measurement design, 18 college women searched for target letters in 18 lists of common words, rare words, and nonwords arranged either vertically or horizontally. The mean search time in seconds for three trials in each of six conditions was expected to be significantly slower for nonwords than for words and for vertical orientations than for horizontal orientations. More importantly, a significant interaction was predicted between direction of search and the type of list searched. Results confirmed earlier findings that the two main effects were significant; the significant interaction provided empirical evidence that consideration needs to be given to both intraword redundancy and direction of visual search.     

Whole-word units are used before orthographic knowledge in perceptual development

A visual search task for target letters in multiletter displays was used to investigate information-processing differences between college students and presecond-grade children (mean age = 7 years, 4 months). The stimulus displays consisted of single words, pronounceable pseudowords, and unpronounceable nonwords varying in length from three to five letters. The mean response times for indicating whether or not a target letter occurred in the display increased with the number of display letters for both groups, although there were apparent differences between groups in the rate of search and type of search strategy used. Pre-second-grade children responded faster to word displays than to pseudoword and nonword displays, indicating that familiar letter strings could be processed faster than unfamiliar strings regardless of whether or not the latter were consistent with rules of English orthography. In contrast, college students processed words and pseudowords about equally well, and both resulted in faster responses than nonwords. As reading skills develop, children apparently come to process familiar words differently from other letter strings. Only after a significant sightword vocabulary is established do children seem to recognize the regularities of standard English orthography and make use of this knowledge to facilitate perceptual processes.     

Distractor effects during processing of words under load

The perceptual load model of attention (Lavie, 1995) suggests that processing of irrelevant distractors depends on the extent to which a relevant task engages full perceptual capacity. Word recognition models suggest that letter perception is facilitated in words relative to nonwords. These models led us to hypothesize that increasing the number of letters would increase perceptual load more for nonwords than for words, and thus would be more likely to exhaust capacity and eliminate distractor processing for nonwords than for words. In support of this hypothesis, we found that increasing the number of search letters increases RTs more for nonwords than for words and only reduces distractor interference for nonwords. Thus, although readers process words more efficiently than nonwords, they also become more prone to distraction when processing words.     

On the process of recognizing inverted words: Does it rely only on orientation-invariant cues?

Following a demonstration by Parks (1983) of failure to notice the reflection of a letter of an inverted word, two experiments were conducted to test a hypothesis about the process of recognizing inverted words that is termed here invariant cues only (ICO)-a letter-by-letter identification process based only on orientation-invariant letter features. In Experiment 1, subjects were presented with whole strings-words and nonwords, either upright or inverted-in which either all the letters were normal or one of the letters was reflected, and they were asked to make lexical decisions. In Experiment 2, subjects made a reflection judgment about an upright or inverted letter within a string immediately after they had been presented with the other, nonreflected string letters, again either upright or inverted. The results do not support the ICO hypothesis: Lexical decisions were greatly affected by the reflection of a letter in upright and inverted stimuli alike. Reflection judgments were considerably facilitated by word context in the upright and the inverted modes alike. The results are accommodated better by the notion that recognition of disoriented words requires some correction used to restore orientation-sensitive features.     

Features versus redundancy: comments on Massaro, Venezky, and Taylor's "Orthographic regularity, positional frequency, and visual processing of letter strings"

Massaro, Venezky, and Taylor (1979) found only a modest effect of familiarity on letter search, apparently because they pitted pseudowords (rather than real words) against nonwords and used lowercase rather than uppercase letters. Precuing the target letter seemed to reduce the familiarity effect they found yet further, but this conclusion is clouded by the fact that reaction time data were compared with accuracy data. Because similarity between target and nontarget letters tended to have more of an effect when familiarity had less of an effect. Massaro et al. proposed a successive model, with features being detected in the first stage and orthographic structure being used in a second stage. However, a concurrent model, with a self-terminating race between lower and higher level processes, can account for the data just as well. Data from Massaro et al. and from Krueger decisively demonstrate that there is a familiarity effect based on sequential redundancy over and above any effect based on spatial redundancy (Mason 1975). The Massaro et al. data also indicate that the relative familiarity effect is constant across various age groups (Krueger, Keen & Rublevich, 1974).     

Cognitive and linguistic factors affect visual feature integration

Five experiments investigated the influence of cognitive and linguistic factors on the integration of color and letter-shape information. Subjects were briefly presented strings of colored letters that varied in pronounceability and familiarity. Detection and search tasks required subjects to identify the color of predesignated target letters. It was proposed that errors in integrating color and shape would be less likely with items from different perceptual units than from items within the same perceptual unit. If words, at some level of perceptual analysis, are processed as units whereas nonwords are processed by individual letters, then there should be more letter-shape and color feature integration errors with words than with nonwords. The first two experiments tested this prediction by comparing feature integration errors with words and nonwords. The remaining experiments manipulated letter-string pronounceability, familiarity, and the presence of vowels to isolate the factors that may influence feature integration. The results demonstrate that cognitive and linguistic factors, such as familiarity and pronounceability, can influence the combination of colors and shapes in perception.     

The relative benefit of word context is a constant proportion of letter identification time

Letter identification is reduced when the target letter is surrounded by other, flanking letters. This visual crowding is known to be impacted by physical changes to the target and flanks, such as spatial frequency content, polarity, and interletter spacing. There is also evidence that visual crowding is reduced when the flanking letters and the target letter form a word. The research reported here investigated whether these two phenomena are independent of each other or whether the degree of visual crowding impacts the benefit of word context. Stimulus duration thresholds for letters presented alone and for the middle letters of 3-letter words and nonwords were determined for stimuli presented at the fovea and at the periphery. In Experiment 1, the benefit of word context was found to be the same at the fovea, where visual crowding is minimal, and at the periphery, where visual crowding is substantial. In Experiment 2, visual crowding was manipulated by changing the interletter spacing. Here, too, the benefit of word context was fairly constant for the two retinal locations (fovea or periphery), as well as with changes in interletter spacing. These data call into question both the idea that the benefit of word context is greater when stimulus quality is reduced (as is the case with visual crowding) and the idea that words are processed more effectively when they are presented at the fovea.     

Lexically guided retuning of letter perception

Participants made visual lexical decisions to upper-case words and nonwords, and then categorized an ambiguous N-H letter continuum. The lexical decision phase included different exposure conditions: Some participants saw an ambiguous letter "?", midway between N and H, in N-biased lexical contexts (e.g., REIG?), plus words with unambiguous H (e.g., WEIGH); others saw the reverse (e.g., WEIG?, REIGN). The first group categorized more of the test continuum as N than did the second group. Control groups, who saw "?" in nonword contexts (e.g., SMIG?), plus either of the unambiguous word sets (e.g., WEIGH or REIGN), showed no such subsequent effects. Perceptual learning about ambiguous letters therefore appears to be based on lexical knowledge, just as in an analogous speech experiment (Norris, McQueen, & Cutler, 2003) which showed similar lexical influence in learning about ambiguous phonemes. We argue that lexically guided learning is an efficient general strategy available for exploitation by different specific perceptual tasks.     

The word superiority effect: Dependence on short-term memory factors

Two experiments were conducted to test whether the word superiority effect, that letters in words are perceived more accurately than letters in nonwords, could be attributed to short-term memory (STM) factors. One hypothesis attributed the word superiority effect to superior maintenance of words in STM. Another hypothesis was that letters in STM have considerable positional uncertainty which is overcome by the orthographic characteristics of the words. Both experiments utilized a simultaneous same-different task, where subjects compared two four-letter strings, one on top of the other, which were presented tachistoscopically. In Experiment I, the two presented strings were either both words or both nonwords and a word superiority effect was obtained. This result was interpreted as disconfirming the STM maintenance hypothesis. In Experiment II, letters were removed from one of the two letter strings, making the serial position of the comparison unambiguous. The word superiority effect disappeared. This result was interpreted as supporting the positional uncertainty hypothesis.     

Effect of direction of sequential presentation and redundancy on short-term recognition memory

Short-term recognition memory was tested by presenting six letters, one after the other, followed by a target letter and having S indicate whether or not the target matched one of the six letters. Recognition memory for a letter was better when it was embedded in a six-letter word, rather than a nonword, and when it was included in a sequence presented left-to-right, rather than right-to-left (Experiment 1). Reducing the presentation rate from 4/sec to 2.5/sec largely eliminated the left-to-right effect (Experiment 2). The effect of direction of presentation was greater for redundant (Experiment 1) than for nonredundant sequences (Experiment 3) and was greater for Ss who more frequently formed a word out of the sequence (Experiments 1 and 2), but was no greater for words than nonwords (Experiments 1 and 2) and no greater for letter than for line-figure sequences (Experiment 3). These findings suggest that the left-to-right effect depends as much, or more, on “peripheral” processes (e.g., eye movements) as on “central” processes (e.g., reading).