Semantic anomalies at the borderline of consciousness: an eye-tracking investigation

We report an eye-tracking study in which participants read passages containing difficult-to-detect semantic anomalies. Would there be any evidence of the registration of the anomaly within the comprehension system (reflected in eye tracking) when anomalies were not noticed? Using early and late processing measures, there was no evidence for registration independent of conscious detection. Comparisons were made between detected and undetected anomalies and between these and nonanomalous controls. There was evidence of disruption to the tracking measures only when a conscious report was also made. These data fit the view that shallow semantic processing underlies the failure to detect anomalies. Implications for language processing are discussed.     

A comparison of semantic and syntactic event related potentials generated by children and adults

The present study employs event related potentials (ERPs) to verify the utility of using electrophysiological measures to study developmental questions within the field of language comprehension. Established ERP components (N400 and P600) that reflect semantic and syntactic processing were examined. Fifteen adults and 14 children (ages 8-13) processed spoken stimuli containing either semantic or syntactic anomalies. Adult participants showed a significant N400 in response to semantic anomalies and P600 components in response to syntactic anomalies. Children also show evidence of both ERP components. The children's N400 component differed from the adults' in scalp location, latency, and component amplitude. The children's P600 was remarkably similar to the P600 shown by adults in scalp location, component amplitude, and component latency. Theoretical implication for theories of language comprehension in adults and children will be discussed.     

Non-conscious word processing in a mirror-masking paradigm causing attentional distraction: an ERP-study

In this event-related potential (ERP) study a masking technique that prevents conscious perception of words and non-words through attentional distraction was used to reveal the temporal dynamics of word processing under non-conscious and conscious conditions. In the non-conscious condition, ERP responses differed between masked words and non-words from 112 to 160 ms after stimulus-onset over posterior brain areas. The early onset of the word-non-word differences was compatible with previous studies that reported non-conscious access to orthographic information within this time period. Moreover, source localisations provided evidence for automatic activation of prelexical phonological information, whereas no evidence for non-conscious semantic processing was found. When subjects were informed about the masking technique, lexical differences occurred at later time intervals, suggesting conscious access to additional word related information. These results indicate that early visual word processing does not depend entirely on attentional resources, but that non-conscious processing probably is restricted to rather lower-level linguistic information.     

Examining the lag effect under incidental encoding: Contributions of semantic priming and reminding

Memory is better when repeated learning events are spaced than when they are massed (spacing effect), as well as when material is processed semantically than when it is processed graphemically (levels-of-processing effect). Examination of the relationship between levels of processing and spacing for both deeply and shallowly encoded items has shown a spacing effect for items processed deeply, but not shallowly. A semantic priming account of spacing was proposed to explain the interaction between levels of processing and spacing on memory. The current study manipulated levels of processing and the amount of spacing (lag) that occurred between repetitions of items that were incidentally encoded. Results from Experiments 1A and 1B revealed lag effects in test performance when items were deeply and shallowly encoded. Although these findings are inconsistent with a semantic priming account, they can be interpreted within a reminding account, which is explored in Experiment 2. Results from the second experiment indicate that bringing reminding under conscious control benefited items that were presented at a long lag but not at a shorter lag. Together, this study provides evidence that is difficult to accommodate with a semantic priming account of spacing and instead provides additional support for a reminding account suggesting that automatic and controlled processes may both underlie the reminding process.     

The nature of change detection and online representations of scenes

This article provides evidence for implicit change detection and for the contribution of multiple memory sources to online representations. Multiple eye-movement measures distinguished original from changed scenes, even when college students had no conscious awareness for the change. Patients with amnesia showed a systematic deficit on 1 class of eye-movement measures of change detection, even though conscious awareness was not required for the effect to be observed. The authors' findings suggest that online representations of scenes are (a) built up across viewings, (b) composed of activated information from both long-term and working memory, and (c) directly compared with currently processed information regarding the external world. Subsequent online processing is influenced by these representations even when the results of the comparison are not accessible for verbal report.     

The effect of semantic context on prospective memory performance

The current study provides evidence for spontaneous processing in prospective memory (PM) or memory for intentions. Discrepancy-plus-search is the spontaneous processing of PM cues via disruptions in processing fluency of ongoing task items. We tested whether this mechanism can be demonstrated in an ongoing rating task with a dominant semantic context. Ongoing task items were manipulated such that the PM cues were members of a semantic category (i.e., Body Parts) that was congruent or discrepant with the dominant semantic category in the ongoing task. Results showed that participants correctly responded to more PM cues when there was a category discrepancy between the PM cues and ongoing task items. Moreover, participants' identification of PM cues was accompanied by faster ongoing task reaction times when PM cues were discrepant with ongoing task items than when they were congruent. These results suggest that a discrepancy-plus-search process supports PM retrieval in certain contexts, and that some discrepancy-plus-search mechanisms may result from the violation of processing expectations within a semantic context.     

Active hippocampus during nonconscious memories

The hippocampal formation is known for its importance in conscious, declarative memory. Here, we report neuroimaging evidence in humans for an additional role of the hippocampal formation in nonconscious memory. We maskedly presented combinations of faces and written professions such that subjects were not aware of them. Nevertheless, the masked presentations activated many of the brain regions that unmasked presentations of these stimuli did. To induce a nonconscious retrieval of the faces and face-associated occupational information, subjects were instructed to view the previously masked faces and to guess the professional category of each person--academic, artist, and workman. Guessing the professional category of previously masked versus new faces activated the left and right hippocampal formation and right perirhinal cortex as well as bilateral fusiform areas and fronto-temporal areas known to mediate the retrieval of semantic information. These activations within the semantic processing system suggest that conceptual knowledge acquired during masking was nonconsciously retrieved. Our data provide clues to an analogous role of the hippocampus in conscious and nonconscious memory.     

Partial awareness creates the "illusion" of subliminal semantic priming

We argue that the lack of consensus regarding the existence of subliminal semantic processing arises from not taking into account the fact that linguistic stimuli are represented across several processing levels (features, letters, word form) that can independently reach or not reach awareness. Using masked words, we constructed conditions in which participants were aware of some letters or fragments of a word, while remaining unaware of the whole word. Three experiments using the Stroop priming paradigm show that when the stimulus set is reduced and participants are encouraged to guess the identity of the prime, such partially perceived stimuli can nonetheless give rise to "semantic" processing. We provide evidence that this effect is due to illusory reconstruction of the incompletely perceived stimulus, followed by usual semantic processing of the result. We conclude that previously reported unconscious Stroop priming is in fact a conscious effect, but applied to a perceptual illusion.     

Comprehending Semantic and Grammatical Violations in Italian. N400 and P600 Comparison with Visual and Auditory Stimuli

Arguments about the existence of language-specific neural systems and specifically about the independence of syntactic and semantic processing have focused on the event-related brain measures (ERPs) as tool to monitoring moment-by-moment the cognitive processes underlaid. In the present experiments, the available evidence indicates that the ERP response to semantic anomalies is at least partially distinct from the ERP response to syntactic anomalies and that two distinct processes are activated in sentences comprehension. ERPs were recorded from 10 electrodes while subjects read (Experiment 1) or listened (Experiment 2) to sentences containing semantic or syntactic violations. Final-words that were inconsistent with the sentence context elicited a negative-going wave at about 400 ms poststimulus, whereas penultimate-word incongruous with the grammatical structure (subject–verb non-agreement) elicited a positive-going wave about 600 ms poststimulus. No differences based on the perceptual modality of the stimulus (visual or auditory) nor different ERP correlates as a function of task-relevance (explicit/implicit task induction) were found. The implications of our results for Italian language are explained.     

Right hemisphere participation in reading

This study examined whether the right hemisphere's contribution to lexical semantic processing is greatest when it is "disinhibited." Skilled reading may require the controlled modulation of interhemispheric interaction: the left hemisphere (or some other control mechanism) may regulate the subprocesses of reading by selectively "inhibiting" and "disinhibiting" right hemisphere function. Right-handed undergraduates concurrently performed two tasks: a lateralized semantic or rhyme task and a verbal memory task. It was hypothesized that right hemisphere reading processes would be disinhibited when the left hemisphere was "occupied" with the memory task. This hypothesis was supported for a subgroup of subjects who showed evidence of inhibition of right hemisphere function (i.e., left hemisphere dominance for lexical processing) when the lateralized semantic task was performed alone. Across subjects, there was a strong correlation between the degree of left hemisphere dominance in the single-task semantic conditions and the degree of disinhibition of right hemisphere function in the dual-task semantic condition.     

Masking procedures can influence priming effects besides their effects on conscious perception

Masked priming has been employed to study the role of consciousness for different levels of visual processing. However, masking procedures differ systematically between studies. To examine these procedural differences we contrasted priming effects with metacontrast masking, which is often applied in the context of perceptual priming, and priming effects with sandwich pattern masking, frequently used in studies on semantic priming. Results indicate that the amount of masking neither affects perceptual nor semantic priming effects in a semantic categorization task when a metacontrast masking paradigm was used. However, perceptual and semantic priming effects increased with increasing prime visibility when a sandwich pattern masking paradigm was used. Findings suggest that different types of masking procedures affect the processing of the masked stimuli in substantially different ways even if the masking effect on conscious perception of these stimuli is comparable.     

See what you want to see: motivational influences on visual perception

People's motivational states--their wishes and preferences--influence their processing of visual stimuli. In 5 studies, participants shown an ambiguous figure (e.g., one that could be seen either as the letter B or the number 13) tended to report seeing the interpretation that assigned them to outcomes they favored. This finding was affirmed by unobtrusive and implicit measures of perception (e.g., eye tracking, lexical decision tasks) and by experimental procedures demonstrating that participants were aware only of the single (usually favored) interpretation they saw at the time they viewed the stimulus. These studies suggest that the impact of motivation on information processing extends down into preconscious processing of stimuli in the visual environment and thus guides what the visual system presents to conscious awareness.     

Selective attention to global and local structure of objects: Alternative measures of nontarget processing

When individuals are asked to report either the global or the local level of structure in a stimulus pattern located inside a relevant object, distractors located within an irrelevant object will interfere only if they are at the same level of structure as that of the target item (Briand, 1993; Paquet & Merikle, 1988). The basis of this level-specific filtering is unclear, as is the true level of semantic analysis for the ignored items. In the present series of experiments, multiple measures of nontarget processing were used to assess concurrent interference, negative priming, and a category effect supposedly reflecting a more abstract level of semantic analysis. These different indicants were assessed in three experiments in which form, color, or a spatial precue was used to direct attention to the relevant stimulus pattern. Overall, cuing by form produced poorer spatial selectivity, whereas spatial precues and color led to better selectivity. However, the three measures of nontarget processing were not equally affected by these manipulations, with global information showing more evidence for semantic analysis than for local analysis regardless of the type of selection cue used. The results suggest that inhibition is not the basis of target selection when ignored items are local, but that it may be used when global items are ignored.     

Are nonconscious processes sufficient to produce false memories?

Seamon, Luo, and Gallo (1998) reported evidence that nonconscious processes could produce false recognition in a converging-associates task, whereby subjects falsely remember a nonstudied lure (e.g., sleep) after studying a list of related words (bed, rest, awake...). Zeelenberg, Plomp, and Raaijmakers (2003) failed to observe this false recognition effect when list word recognition was at chance. We critically evaluate the evidence for nonsconscious processing and report the results of a new experiment designed to overcome previous methodological limitations. Consistent with Seamon et al., we found that conscious activation of a related lure during study was not necessary for its subsequent recognition; consistent with Zeelenberg et al., we found no evidence for recognition of related lures under conditions where there was no memory for studied words. It is currently unknown whether conscious recollection of the studied items is necessary for false recognition or if nonconscious activation of the lure is sufficient.     

Think different: the merits of unconscious thought in preference development and decision making

The role of unconscious and conscious thought in decision making was investigated in 5 experiments. Because of the low processing capacity of consciousness, conscious thought was hypothesized to be maladaptive when making complex decisions. Conversely, unconscious thought was expected to be highly effective. In Experiments 1-3, participants were presented with a complex decision problem in which they had to choose between various alternatives, each with multiple attributes. Some participants had to make a decision immediately after being presented with the options. In the conscious thought condition, participants could think about the decision for a few minutes. In the unconscious thought condition, participants were distracted for a few minutes and then indicated their decision. Throughout the experiments, unconscious thinkers made the best decisions. Additional evidence obtained in Experiments 4 and 5 suggests that unconscious thought leads to clearer, more polarized, and more integrated representations in memory.     

Brain potentials elicited by prose-embedded linguistic anomalies

Linguistic theories distinguish between syntax (sentence form) and semantics (sentence meaning). Correspondingly, recent studies have shown that syntactic and semantic anomalies elicit distinct changes in the event-related brain potential (ERP). However, these results have been obtained with highly artificial methodologies and have not yet been generalized to more natural reading conditions. Here, we recorded ERPs while subjects read a naturalistic prose passage. The subjects either read for comprehension with no other task being assigned or read for comprehension and made acceptability judgments after each sentence. Consistent with prior work and regardless of the subjects' assigned task, syntactic anomalies elicited a large positive wave (P600), whereas semantic anomalies elicited a large increase in N400 amplitude. These results demonstrate that the qualitatively distinct ERP responses elicited by syntactic and semantic anomalies are not artifacts of unnatural aspects of previously used stimuli, thereby providing additional evidence that separable syntactic and semantic processes exist.     

Unconscious processing modulates creative problem solving: Evidence from an electrophysiological study

Previous behavioral studies have identified the significant role of subliminal cues in creative problem solving. However, neural mechanisms of such unconscious processing remain poorly understood. Here we utilized an event-related potential (ERP) approach and sandwich mask technique to investigate cerebral activities underlying the unconscious processing of cues in creative problem solving. College students were instructed to solve divergent problems under three different conditions (conscious cue, unconscious cue and no-cue conditions). Our data showed that creative problem solving can benefit from unconscious cues, although not as much as from conscious cues. More importantly, we found that there are crucial ERP components associated with unconscious processing of cues in solving divergent problems. Similar to the processing of conscious cues, processing unconscious cues in problem solving involves the semantic activation of unconscious cues (N280–340) in the right inferior parietal lobule (BA 40), new association formation (P350–450) in the right parahippocampal gyrus (BA 36), and mental representation transformation (P500–760) in the right superior temporal gyrus (BA 22). The present results suggest that creative problem solving can be modulated by unconscious processing of enlightening information that is weakly diffused in the semantic network beyond our conscious awareness.     

Individual differences in mature readers in reading, spelling, and grapheme-phoneme conversion

Individual differences in word recognition, spelling, verbal reasoning, frequency of print exposure, phonological skills, Gestalt processing and semantic processing were examined in 110 university undergraduates. Most reading and phonological tasks involved making sequences of lexical decisions through lists of common stimuli within set time limits. The test measures were percentages correct adjusting for chance. The main findings were as follows: First, there is a substantial “Matthew effect” in that good readers were also good at spelling, good at handling the meaning of words, and appeared to have had the most print exposure. Second, phonological skills appear to be independent of lexical skills. Furthermore, within these phonological skills there appear to be two components, one that is automatic, and one that is more of a conscious operation.     

Individual differences in mature readers in reading,spelling, and grapheme-phoneme conversion

Individual differences in word recognition, spelling, verbal reasoning, frequency of print exposure, phonological skills, Gestalt processing and semantic processing were examined in 110 university undergraduates. Most reading and phonological tasks involved making sequences of lexical decisions through lists of common stimuli within set time limits. The test measures were percentages correct adjusting for chance. The main findings were as follows: First, there is a substantial “Matthew effect” in that good readers were also good at spelling, good at handling the meaning of words, and appeared to have had the most print exposure. Second, phonological skills appear to be independent of lexical skills. Furthermore, within these phonological skills there appear to be two components, one that is automatic, and one that is more of a conscious operation.     

Social inference and individual differences in aggression: Evidence for spontaneous judgments of hostility

This research examined the hypothesis that aggressive vs. nonaggressive individuals differ in their spontaneous trait inferences, i. e., inferences made without any conscious intention of inferring characteristics of an actor. We anticipated that spontaneous processing conditions would be more revealing of aggressive/nonaggressive differences than would conditions that prompt deliberate inference processes. We used a cued-recall paradigm. Aggressive and nonaggressive subjects were instructed to memorize sentences that were open to either hostile or nonhostile interpretations. Sentence recall was then cued by either hostile dispositional terms or by words that were linked semantically to the element of the sentences. Within the spontaneous inference condition, semantic cues prompted twice as much recall as hostile cues among nonaggressive subjects, whereas dispositional cues aided recall more than semantic cues among aggressive subjects. As predicted, within the delinerate inference conditions there were no aggressive/nonaggressive differences. The nature of spontaneous vs. deliberate inferential processes and the advantages of spontaneous inference paradigms for testing predictions about schema-based processing in aggression are discussed. © 1995 Wiley-Liss, Inc.