Modulating semantic feedback in visual word recognition

Stimulus-response compatible orienting and the effect of an action not taken: Perception delayed is automaticity denied

Orienting to a signal source is widely viewed as automatic in the sense that it is triggered by the stimulus. However, this behavior is typically assessed in a context in which the subject knows beforehand what he or she has to do. In the present experiments, the role of task set was investigated by having the response vary randomly from trial to trial. On some trials, a cue signaled the subject to respond, and on the remaining trials, another cue signaled the subject to withhold a response. Stimulus contrast and temporal overlap between task cue and target were manipulated. The effect of a reduction in stimulus contrast was sometimes absorbed into the time taken to decode the cue, but critically, other times not. These results highlight the theoretical importance of considering task set as an essential element in processing, and they undermine the theoretical claim that putatively automatic processes are not subject to interference from other mental activities.

Top-down modulation of ventral occipito-temporal responses during visual word recognition

Although interactivity is considered a fundamental principle of cognitive (and computational) models of reading, it has received far less attention in neural models of reading that instead focus on serial stages of feed-forward processing from visual input to orthographic processing to accessing the corresponding phonological and semantic information. In particular, the left ventral occipito-temporal (vOT) cortex is proposed to be the first stage where visual word recognition occurs prior to accessing nonvisual information such as semantics and phonology. We used functional magnetic resonance imaging (fMRI) to investigate whether there is evidence that activation in vOT is influenced top-down by the interaction of visual and nonvisual properties of the stimuli during visual word recognition tasks. Participants performed two different types of lexical decision tasks that focused on either visual or nonvisual properties of the word or word-like stimuli. The design allowed us to investigate how vOT activation during visual word recognition was influenced by a task change to the same stimuli and by a stimulus change during the same task. We found both stimulus- and task-driven modulation of vOT activation that can only be explained by top-down processing of nonvisual aspects of the task and stimuli. Our results are consistent with the hypothesis that vOT acts as an interface linking visual form with nonvisual processing in both bottom up and top down directions. Such interactive processing at the neural level is in agreement with cognitive and computational models of reading but challenges some of the assumptions made by current neuro-anatomical models of reading.

Semantic priming occurs for word but not location pronunciation in the postcue task

Semantic priming refers to the finding that a word response is facilitated if it is preceded by a related word compared to when it is preceded by an unrelated word. Dallas and Merikle (Can J Psychol 30: 15-21 1976a; Bull Psychon Soc 8: 441-444 1976b) demonstrated that semantic priming occurred under conditions in which a pair of simultaneously displayed words was previewed for over a second prior to the onset of a cue indicating which of the words should be pronounced aloud (postcue task). In contrast, semantic interference effects have been reported for postcue picture-naming tasks (Dean et al. in J Exp Psychol Learn Mem Cogn 27: 733-743, 2001; Humphreys et al. in J Exp Psychol Learn Mem Cogn 21: 961-980, 1995). According to Dean et al., the semantic interference effects in postcue picture naming occur because the integration of the object and the cued attribute in memory is more difficult for categorically related pictures than for unrelated pictures. The aim of this experiment was to determine whether this idea was true for postcue word pronunciation tasks. Participants completed two postcue tasks, one requiring pronunciation of the target word indicated by a locational cue and another requiring pronunciation of the location of a centrally presented word. Results indicated a semantic priming effect only for the locational cue condition suggesting that the integration of the cue and identity information was unaffected by word context. These data suggest that priming in a postcue word pronunciation task may be due to feedback from residual activation within the semantic system facilitating access to the target word's phonology.

Automatic semantic feedback during visual word recognition

Four experiments were conducted to determine whether semantic feedback spreads to orthographic and/or phonological representations during visual word recognition and whether such feedback occurs automatically. Three types of prime-target word pairs were used within the mediated-priming paradigm: (1) homophonically mediated (e.g.,frog-[toad]-towed), (2) orthographically mediated (e.g.,frog-[toad]-told), and (3) associatively related (e.g.,frog-toad). Using both brief (53 msec; Experiment 1) and long (413 msec; Experiment 3) prime exposure durations, significant facilitatory-priming effects were found in the response time data with orthographically, but not homophonically, mediated prime-target word pairs. When the prime exposure duration was shortened to 33 msec in Experiment 4, however, facilitatory priming was absent with both orthographically and homophonically mediated word pairs. In addition, with a brief (53-msec) prime exposure duration, direct-priming effects were found with associatively (e.g.,frog-toad), orthographically (e.g., toad-told), and homophonically (e.g., toad-towed) related word pairs in Experiment 2. Taken together, these results indicate that following the initial activation of semantic representations, activation automatically feeds back to orthographic, but not phonological, representations during the early stages of word processing. These findings were discussed in the context of current accounts of visual word recognition.

Basic processes in reading: a critical review of pseudohomophone effects in reading aloud and a new computational account

There are pervasive lexical influences on the time that it takes to read aloud novel letter strings that sound like real words (e.g., brane from brain). However, the literature presents a complicated picture, given that the time taken to read aloud such items is sometimes shorter and sometimes longer than a control string (e.g.,frane) and that the time to read aloud is sometimes affected by the frequency of the base word and other times is not. In the present review, we first organize these data to show that there is considerably more consistency than has previously been acknowledged. We then consider six different accounts that have been proposed to explain various aspects of these data. Four of them immediately fail in one way or another. The remaining two accounts may be able to explain these findings, but they either make counterintuitive assumptions or invoke a novel mechanism solely to explain these findings. A new account is advanced that is able to explain all of the effects reviewed here and has none of the problems associated with the other accounts. According to this account, different types of lexical knowledge are used when pseudohomophones and nonword controls are read aloud in mixed and pure lists. This account is then implemented in Coltheart, Rastle, Perry, Langdon, and Ziegler's (2001) dual route cascaded model in order to provide an existence proof that it accommodates all of the effects, while retaining the ability to simulate three standard effects seen in nonword reading aloud.

Parallel distributed processing and lexical-semantic effects in visual word recognition: Are a few stages necessary?

D. C. Plaut and J. R. Booth (2000) presented a parallel distributed processing model that purports to simulate human lexical decision performance. This model (and D. C. Plaut, 1995) offers a single mechanism account of the pattern of factor effects on reaction time (RT) between semantic priming, word frequency, and stimulus quality without requiring a stages-of-processing account of additive effects. Three problems are discussed. First, no evidence is provided that this model can discriminate between words and nonwords with the same orthographic structure and still produce the pattern of factor effects on RT it currently claims to produce. Second, the level of representation used by the model to make a lexical decision is inconsistent with what is known about how skilled readers with damage to their semantic system make word/nonword discriminations. Finally, there are a number of results that are difficult to reconcile with the single mechanism account. The authors' preference is to retain the stages-of-processing account.

Single letter coloring and spatial cuing eliminates a semantic contribution to the Stroop effect

Previous work has shown that the Stroop effect is reduced in size when a single letter is colored and spatially precued. The present experiment addresses a number of criticisms of this work by (1) providing a direct measure of semantic processing, (2) using a vocal response instead of a manual one, and (3) using a more appropriate baseline. A semantically based Stroop effect (slower color naming for color-associated words than for color-neutral words) is observed when all letters in the display are precued and appear in a homogeneous color. This Stroop effect is statistically eliminated when a single letter is precued and is the "odd man out" in terms of its color. Two explanations are considered. In one, single-letter coloring and cuing serve to curtail semantic processing. In the other, single-letter coloring and cuing help to keep the informational sources (i.e, color, word) separate and hence reduce interference, but semantic analysis is not curtailed. The latter account provides a more complete account of existing data.

Identification Facilitation for Emotionally Arousing Verbs During the Attentional Blink

The present study aimed to examine affective modulation of the "attentional blink" effect during rapid serial visual presentation (RSVP). Pleasant, neutral, and unpleasant written verbs were used as a 2nd target (T2) in an 8.6-Hz RSVP paradigm. Pronounced effects of 1st target (T1)-T2 stimulus onset asynchrony (SOA) were found, showing reduced report accuracy for 232- and 464-ms SOAs. Affectively arousing (pleasant and unpleasant) T2s were associated with enhanced accuracy compared with neutral T2s specifically during short (232 ms) SOAs. In contrast, pleasant and unpleasant T2s rated low in terms of emotional arousal did not show this enhancement. These results suggest that affectively arousing information is selected preferentially from a temporal stream, facilitating processes such as working memory consolidation and action.

Semantic processing in visual word recognition: activation blocking and domain specificity

Lexical decision to a target is typically facilitated when a related prime is simply read, but is typically eliminated if subjects carry out a letter search on the prime when probe and prime appear simultaneously. Three experiments involving the addition of a task-irrelevant word to this prime search paradigm address (1) Stolz and Besner's (1996, 1998) account in which semantic priming is eliminated because letter search on the prime instantiates an activation block between lexical and semantic levels of representation, (2) Chiappe, Smith, and Besner's (1996) account that activation blocking is domain specific, and (3) Neely and Kahan's (2001) claim that semantic activation is context independent and capacity free. The results are (1) consistent with the account that activation blocking is general to a level, rather than item specific, (2) consistent with the account that activation blocking is domain specific, and (3) inconsistent with the claim that semantic activation is context independent and capacity free.