Detection of Fs in a single statement: the role of phonetic recoding

Individual differences in working memory capacity and visual search while reading

Individual differences in working memory capacity are related to variations in a wide range of cognitive tasks. Surprisingly, effects of individual differences in working memory capacity are somewhat limited in visual search tasks. Here we tested the hypothesis that such an effect would be robust when search was one component of a dual task. Participants were presented strings of letters using rapid serial visual presentation and were required to detect all instances of a particular target letter. In Experiment 1, participants performed the letter search task in three contexts, while: (a) reading a prose passage, (b) processing a stream of random words, or (c) processing a random stream of non-words. In the absence of the dual task of reading prose, and in line with much of the literature on individual differences in working memory capacity and visual search, search performance was unaffected by working memory capacity. As hypothesized, however, higher working memory capacity participants detected more target letters than lower capacity participants in the "true" dual task (searching while reading prose). The hypothesized results from the prose passage were replicated in Experiment 2. These results show that visual search efficiency is dramatically affected by working memory capacity when searching is combined with another cognitive task but not when it is performed in isolation. Our findings are consistent with recent suggestions that visual search efficiency will be affected by working memory capacity so long as searching is embedded in a context that entails managing resource allocation between concurrent tasks.

The impact of familiarization strategies on the missing-letter effect

When reading a text and searching for a target letter, readers make more omissions of the target letter if it is embedded in frequent function words than if it is in rare content words. While word frequency effects are consistently found, few studies have examined the impacts of passage familiarity on the missing-letter effect and studies that have present conflicting evidence. The present study examines the effects of passage familiarity, as well as the impacts of passage familiarization strategy promoting surface or deep encoding, on the missing-letter effect. Participants were familiarized with a passage by retyping a text, replacing all common nouns with synonyms, or generating a text on the same topic as that of the original text, and then completed a letter search task on the familiar passage as well as an unfamiliar passage. In Experiment 1, when both familiar and unfamiliar passages use the same words, results revealed fewer omissions for the retyping and synonyms conditions. However, in Experiment 2, when different words are used in both types of texts, no effect of familiarization strategy was observed. Furthermore, the missing-letter effect is maintained in all conditions, adding support to the robustness of the effect regardless of familiarity with the text.

What a Simple Letter-Detection Task Can Tell Us About Cognitive Processes in Reading

Understanding reading is a central issue for psychology, with major societal implications. Over the past five decades, a simple letter-detection task has been used as a window on the psycholinguistic processes involved in reading. When readers are asked to read a text for comprehension while marking with a pencil all instances of a target letter, they miss some of the letters in a systematic way known as the missing-letter effect. In the current article, we review evidence from studies that have emphasized neuroimaging, eye movement, rapid serial visual presentation, and auditory passages. As we review, the missing-letter effect captures a wide variety of cognitive processes, including lexical activation, attention, and extraction of phrase structure. To account for the large set of findings generated by studies of the missing-letter effect, we advanced an attentional-disengagement model that is rooted in how attention is allocated to and disengaged from lexical items during reading, which we have recently shown applies equally to listening.

The Missing-Phoneme Effect in Aural Prose Comprehension

When participants search for a target letter while reading for comprehension, they miss more instances if the target letter is embedded in frequent function words than in less frequent content words. This phenomenon, called the missing-letter effect, has been considered a window on the cognitive mechanisms involved in the visual processing of written language. In the present study, one group of participants read two texts for comprehension while searching for a target letter, and another group listened to a narration of the same two texts while listening for the target letter's corresponding phoneme. The ubiquitous missing-letter effect was replicated and extended to a missing-phoneme effect Item-based correlations between the reading and listening tasks were high, which led us to conclude that both tasks involve cognitive processes that reading and listening have in common and that both processes are rooted in psycholinguistically driven allocation of attention.

Letter detection: A window to unitization and other cognitive processes in reading text

Experiments are reviewed that use the letter-detection task, in which subjects read text and circle target letters. Evidence is provided that the letter-detection task reveals the processing units used in reading text and is influenced as well by visual, phonetic, and a combination of semantic and syntactic factors. Specifically, it is shown that circling a target letter in a word depends on the familiarity of the word's visual configuration, the location of the word in the reader's visual field, the phonetic representation of the letter in the word, and a combination of the word's meaning and its grammatical function.

Can skilled readers perform a second task in parallel? A functional connectivity MRI study

When asked to search for a target letter while reading, the patterns with which people miss the target letter reveal information about the process of reading itself. Questions remain as to whether this paradigm reflects normal reading processes however. We used a novel continuous-performance neuroimaging paradigm to address this question. In separate scanning runs, subjects either read alone, read while searching for a target letter, or searched non-words continuously. Functional connectivity analysis recovered the full extent of brain areas identified for reading in a localizer scan, with no differences between reading alone and the dual task condition. Differences were found, however, between both reading conditions and the nonword search condition. These results demonstrate that in skilled readers brain activation associated with reading is unaffected by a concurrent letter-search task. They further demonstrate the utility of a naturalistic, continuous-performance paradigm for studying the neural basis of language processing.

Effects of grammatical categories on letter detection in continuous text

The present study focuses on the interplay between the linguistic principles and the psycholinguistic processes involved in reading. Results from 56 participants on a letter detection task reveal that readers do not process all function words in the same manner. Omission rates were highest for function words occupying the head of maximal projections such as complementizers and determiners. Prepositions were shown to occupy an intermediary position between content and function words, with omission rates varying depending on their semantic load. Together these results appear to bolster and offer a finer grained picture of the role of function words within the framework of both the Guidance Organization (Greenberg et al. in Psychon Bull Rev 11(3):428-433, 2004) and Attentional Disengagement (Roy-Charland et al. in Percept Psychophys 69(3):324-337, 2007) reading models. The results of the present study are discussed using an X-bar theory approach with the goal of refining the structural account of letter detection errors.

The influence of multiple readings on the missing-letter effect revisited

In searching for a target letter while reading, participants make more omissions when the target letter is embedded in frequent function words than when it is embedded in less frequent content words. According to the guidance-organization (GO) model, this occurs because high-frequency function words are processed faster than low-frequency content words, leaving less time available for letter processing. We tested this hypothesis in three experiments by increasing word-processing speed through text repetition, which should translate into higher omission rates. Participants either read the text and searched for the target letter once or read the text three times and searched for a target letter on all readings or the final reading only. In all the experiments in which participants could not anticipate the target letter to be used, results revealed the presence of a large missing-letter effect that was unaffected by familiarity with the text. In addition, when participants knew from the start the target letter to be used on the final reading, the missing-letter effect was eliminated. Repeated search of the same text for different targets increased omissions equally for function words and content words, but this finding was present even when a new text was used, suggesting that repetition of the search task, rather than familiarity with the text, was responsible.

Graphemes are perceptual reading units

Graphemes are commonly defined as the written representation of phonemes. For example, the word 'BREAD' is composed of the four phonemes /b/, /r/, /e/ and /d/, and consequently, of the four graphemes 'B', 'R', 'EA', and 'D'. Graphemes can thus be considered the minimal 'functional bridges' in the mapping between orthography and phonology. In the present study, we investigated the hypothesis that graphemes are processed as perceptual units by the reading system. If the reading system processes graphemes as units, then detecting a letter in a word should be harder when this letter is embedded in a multi-letter grapheme than when it corresponds to a single-letter grapheme. In Experiment 1A, done in English, participants were slower to detect a target letter in a word when the target letter was embedded in multi-letter grapheme (i.e. 'A' in 'BEACH') than when it corresponded to a single-letter grapheme (i.e. 'A' in 'PLACE'). In Experiment 1B, this effect was replicated in French. In Experiment 2, done in English, this grapheme effect remained when phonemic similarity between the target letter alone and the target letter inside the word was controlled. Together, the results are consistent with the assumption that graphemes are processed as perceptual reading units in alphabetic writing systems such as English or French.

Semantic, phonological, and perceptual changes following left and right intracarotid injection (Wada) with a low amytal dosage

Intracarotid injection of a low dosage of amobarbital (75 mg, 5% solution) was studied in 30 temporal lobectomy candidates while naming achromatic, incongruously, and congruously colored pictorial objects and reading real, nonsense, and embedded words. Semantic errors and phonological alexia followed the left injection, while the right injection induced visuoperceptual errors. When the contralateral hemisphere was anesthetized, the left brain formulated supraordinate categories for words and objects, while the right brain applied concrete labels. The basic language proficiency of patients influenced recovery and outcome; left temporal patients who were interictally anomic performed especially poorly after both injections. Codifying phonological and perceptual changes during the intracarotid amobarbital procedure can improve interpretations about language laterality and organization.

Detecting phonemes and letters in text: interactions between different types and levels of processes

In six experiments, subjects detected phonemes or letters in text presented auditorily or visually. Experiments 1 and 2 provided support for the hypothesis that a mismatch between the phoneme and letter representations of a target leads to detection errors. In addition, visual word unitization processes were implicated. Experiments 3 and 4 provided support for the hypothesis that the Gestalt goodness of pattern affected detection errors when subjects searched for letters. Experiments 5 and 6 demonstrated that the effects of unitization on the detection of letters in common words were decreased by altering the familiar configuration of the test words. The combined results of all six experiments lead to the conclusion that both visual and phonetic processes influence letter detection, that these processes communicate through a type of cross-checking, and that there are at least two levels of visual (and perhaps of phonetic) processing involved in the letter detection task.

The effects of syntactic structure on letter detection in adjacent function words

In the present study, we examined letter detection in very frequent function-word sequences. It has been claimed that such sequences are processed in a unitized manner, thus preempting access to their constituent letters. In contrast, we showed that letter detection in the words for and the (1) was no more difficult when the words appeared in adjacent locations in a sentence (familiar) than when they appeared apart (less familiar sequence) and (2) was contingent upon the words' syntactic roles within the phrase. Thus, letter detection in for was easier when the sequence was separated by a clause boundary than when the words were part of the same clause. The advantage derived from clause separation was strongest when a comma divided clauses. These results challenge the unitization account of the "missing-letter" effect in common phrases and support a position where this phenomenon is seen to reflect the extraction of phrase structure during reading.

The word-superiority effect and phonological recoding

Previous work indicates that the locus of the word-superiority effect in letter detection is nonvisual and that letter names, but not letter shapes, are more accessible in words than in nonwords, that is, scrambled collections of letters (e.g., Krueger & Shapiro, 1979; Krueger & Stadtlander, 1991; Massaro, 1979). The nonvisual (verbal or lexical) coding may be phonological, or it may be more abstract. In the present study, a word advantage in the speed of letter detection was found even when the target letter was silent in the six-letter test word (e.g., s in island). Other test words varied in their frequency of occurrence in English and number of syllables (1, 2, or 3). The word advantage was larger for higher frequency words but was not affected by syllable length. The presence of unpronounceable nonwords and silent letters in the words discouraged reliance upon the phonological code but did not thereby eliminate the word advantage. Thus, the word-superiority effect with free viewing is not based entirely upon phonological recoding.