Study-test awareness can enhance priming on an implicit memory task: evidence from a word completion task

The role of study-test awareness in implicit memory tasks has been an open question for some time. This study investigated the possibility that study-test awareness may enhance priming on an implicit memory task. In three experiments, subjects studied words under levels of processing conditions (nonsemantic vs. semantic) and then received a word stem completion priming task. The results of all three experiments showed that study-test awareness had no effect on priming for nonsemantic study but it did on semantic study, significantly enhancing priming for that study condition. The results are interpreted according to an involuntary aware memory framework.     

Automatic processing of psychological distance: evidence from a Stroop task

A picture-word version of the Stroop task was used to test the automatic activation of psychological distance by words carrying various senses of psychological distance: temporal (tomorrow, in a year), social (friend, enemy), and hypotheticality (sure, maybe). The pictures implied depth, with the words appearing relatively close to or distant from the observer. The participants classified the spatial distance of words faster when the word's implicit psychological distance matched its spatial distance (e.g., a geographically close word was classified faster when it was "friend" than when it was "enemy"). The findings are consistent with the idea that psychological distance is accessed automatically, even when it is not directly related to people's current goals, and suggest that psychological distance is an important dimension of meaning, common to spatial distance, temporal distance, social distance, and hypotheticality.     

Perception without awareness: perspectives from cognitive psychology

Four basic approaches that have been used to demonstrate perception without awareness are described. Each approach reflects one of two types of experimental logic and one of two possible methods for controlling awareness. The experimental logic has been either to demonstrate a dissociation between a measure of perception with awareness and a measure that is sensitive to perception without awareness or to demonstrate a qualitative difference between the consequences of perception with and without awareness. Awareness has been controlled either by manipulating the stimulus conditions or by instructing observers on how to distribute their attention. The experimental findings based on all four approaches lead to the same conclusion; namely, stimuli are perceived even when observers are unaware of the stimuli. This conclusion is supported by results of studies in which awareness has been assessed with either objective measures of forced-choice discriminations or measures based on verbalizations of subjective conscious experiences. Given this solid empirical support for the concept of perception without awareness, a direction for future research studies is to assess the functions of information perceived without awareness in determining what is perceived with awareness. The available evidence suggests that information perceived without awareness both biases what stimuli are perceived with awareness and influences how stimuli perceived with awareness are consciously experienced.     

Attentional orienting and awareness: evidence from a discrimination task

We used several cue–target SOAs (100, 500, 1000 ms) and three different degrees of cue predictability (Non-predictive-50%, Predictive-75%, Counter-predictive-25%), to investigate the role of awareness of cue–target predictability on cueing effects. A group of participants received instructions about the informative value of the cue, while another group did not receive such instructions. Participants were able to extract the predictive value of a spatially peripheral cue and use it to orient attention, whether or not specific instructions about the predictive value of the cue were given, and no matter their ability to correctly report it in a post-test questionnaire. In the non-predictive block, bad estimators who received no instructions showed regular cueing effects, while good estimators exhibited smaller and non-significant facilitatory effects at the short SOA and an absence of significant IOR at longer SOAs. However, for the instructions group, the pattern of results reversed.     

Social presence effects in the Stroop task: further evidence for an attentional view of social facilitation

In contrast with R. B. Zajonc's (1965) classic view about social facilitation-inhibition (SFI) effects, it was found that the presence of relatively unpredictable audiences and forced social comparison with a slightly superior coactor both facilitated performance in the Stroop task while inhibiting automatic verbal processing. Not only do these findings reveal that social presence can help inhibit the emission of dominant responses, providing further support for an attentional view of SFI effects, but they also demonstrate the power of social situations over what has been thought to be invariant automatic processing. As such, they are inconsistent with the view reiterated in more than 500 articles on Stroop interference over the past 60 years and suggest that more attention should be paid to the situations in which cognition takes place.     

The influence of mere social presence on Stroop interference: New evidence from the semantically-based Stroop task

Several studies have shown that mere social presence reduces Stroop interference but processes underlying such effect are still poorly understood. Given that the standard Stroop task used in those studies confounds semantic and response competition, it remains unclear whether Stroop words are processed normally (Sharma, Booth, Brown, & Huguet, 2010) or whether the processing of their semantic representations is altered (Huguet, Galvaing, Monteil, & Dumas, 1999, Exp. 1). The direct evidence from the semantically-based Stroop task (i.e., a task that is free of response competition and thus isolates the semantic component of the Stroop interference, Neely & Kahan, 2001) provided in this paper attests normal semantic processing. Such result refutes the idea that semantic activation can be prevented or controlled by social presence and thus adds to the growing body of evidence showing that semantic activation is indeed automatic. Also importantly, this paper offers an alternative explanation of past findings, which holds that social presence simply reduces the response competition that occurs in the standard Stroop task and sheds some light on the processes that underlie social-facilitating effects of mere presence in the Stroop task.     

Threat processing in obsessive-compulsive disorder: evidence from a modified negative priming task

Individuals with obsessive-compulsive disorder (OCD) often experience intrusive thoughts. These intrusions may be due to biases in information processing mechanisms, including attention, memory, and learning. To examine this hypothesis, we presented a modified negative priming (NP) paradigm with idiographically selected words to 19 individuals with OCD (OCs) and 19 matched non-anxious control participants (NACs). The words included OCD-relevant threat, OCD-relevant positive, and neutral words. This paradigm typically elicits positive priming because participants may learn the contingency between the prime and probe that facilitates responding [Frings and Wentura (2006). Strategy effects counteract distractor inhibition: NP with constantly absent probe distractors. Journal of Experimental Psychology: Human Perception and Performance, 32, 854-864]. As predicted, NACs showed facilitation (i.e., positive priming) rather than NP for all word types, whereas OCs exhibited facilitation for only neutral words. For positive words, OCs exhibited no priming and for threat words they exhibited NP. These results suggest that for idiographic, OCD-relevant threat information, individuals with OCD show difficulty learning the contingency between the information in the prime and probe displays relative to the NACs.     

Perception without awareness in a dichoptic viewing situation

One way of investigating perception without awareness is to utilize the phenomenon of binocular rivalry. The dichoptic viewing situation can be so arranged that a stimulus may be above identification level (when presented alone) but masked by contiguous stimulation, i.e. a brighter image to the other eye. This experimental situation was used to replicate an experiment of Smith et al. (1959) which claimed to demonstrate that differences in meaning between words registered below recognition threshold could affect associated conscious thoughts. In the two experiments reported here, a neutral face was paired with affect words presented subliminally and subjects were asked to rate its expression using a forced-choice indicator. Additional controls to those of Smith et al. were used. In Expt. I it was established that words presented outside of awareness had an effect on semantically related judgements, which was at least as great as that with the same words presented supraliminally. In Expt. II this was confirmed and it was found that increasing the similarity of contour between critical and control words of different meaning suggested differences between subliminal and supraliminal sessions. Responses tended to be meaning-related in the former and structure-related in the latter. It was suggested that the experiments have relevance to current theories of selective attention.     

Role of Gestalt grouping in selective attention: evidence from the Stroop task

Selective attention has been intensively studied using the Stroop task. Evidence suggests that Stroop interference in a color-naming task arises partly because of visual attention sharing between color and word: Removing the target color after 150 msec reduces interference (Neumann, 1986). Moreover, removing both the color and the word simultaneously reduces interference less than does removing the color only (La Heij, van der Heijden, & Plooij, 2001). These findings could also be attributed to Gestalt grouping principles, such as common fate. We report three experiments in which the role of Gestalt grouping was further investigated. Experiment I replicated the reduced interference, using words and color patches. In Experiment 2, the color patch was not removed but only repositioned (<2 degrees) after 100 msec, which also reduced interference. In Experiment 3, the distractor was repositioned while the target remained stationary, again reducing interference. These results indicate a role for Gestalt grouping in selective attention.     

Further evidence that negative priming in the Stroop color-word task is equivalent in older and younger adults

In 2 experiments, possible adult age differences in negative priming were explored using several variants of the Stroop color-word task. Negative priming was at least as high in the older adults as in the younger adults in every variant. Negative priming varied as a function of condition, but the age equivalence was unaffected. This result was true even when the possibility of general slowing was taken into account. Across conditions, interference and negative priming were positively correlated. The results do not permit a clear choice between the 2 major theoretical explanations of negative priming, inhibition and memory retrieval; they do show that negative priming can be systematically manipulated within an experimental paradigm.     

Links between conscious awareness and response inhibition: evidence from masked priming

Recent results from “subliminal priming” experiments have shown that masked prime stimuli which can not be consciously perceived can trigger response activation processes, but that these response activations can later be subject to inhibition. Links between conscious awareness and response inhibition were investigated by manipulating the visibility of masked prime stimuli, from clearly visible primes to prime stimuli that were inaccessible to conscious perception. Response inhibition was observed with unperceived prime stimuli, but not for suprathreshold primes. Correlations between individual prime identification thresholds and the onset of response inhibition indicate that the absence or presence of conscious awareness can predict whether or not response inhibition is elicited. These results demonstrate qualitative differences in the effects of conscious and unconscious information. It is argued that response facilitation produced by consciously available perceptual information can counteract automatic effects of self-inhibitory motor control circuits.     

Perceptual awareness and categorical representation of faces: evidence from masked priming

How internal categories influence how we perceive the world is a fundamental question in cognitive sciences. Yet, the relation between perceptual awareness and perceptual categorization has remained largely uncovered so far. Here, we addressed this question by focusing on face perception during subliminal and conscious perception. We used morphed continua between two face identities and we assessed, through a masked priming paradigm, the perceptual processing of these morphed faces under subliminal and supraliminal conditions. We found that priming from subliminal faces followed linearly the information present in the primes, while priming from visible faces revealed a non-linear profile, indicating a categorical processing of face identities. Our results thus point to a special relation between perceptual awareness and categorical processing of faces, and support the dissociation between two modes of information processing: a subliminal mode involving analog treatment of stimuli information, and a supraliminal mode relying on discrete representation.     

Perception as evidence accumulation and Bayesian inference: insights from masked priming

The authors argue that perception is Bayesian inference based on accumulation of noisy evidence and that, in masked priming, the perceptual system is tricked into treating the prime and the target as a single object. Of the 2 algorithms considered for formalizing how the evidence sampled from a prime and target is combined, only 1 was shown to be consistent with the existing data from the visual word recognition literature. This algorithm was incorporated into the Bayesian Reader model (D. Norris, 2006), and its predictions were confirmed in 3 experiments. The experiments showed that the pattern of masked priming is not a fixed function of the relations between the prime and the target but can be changed radically by changing the task from lexical decision to a same-different judgment. Implications of the Bayesian framework of masked priming for unconscious cognition and visual masking are discussed.     

Context-dependent brightness priming occurs without visual awareness

Our visual systems account for stimulus context in brightness perception, but whether such adjustments occur for stimuli that we are unaware of has not been established. We therefore assessed whether stimulus context influences brightness processing by measuring unconscious priming with metacontrast masking. When a middle-gray disk was presented on a darker (or brighter) background, such that it could be consciously perceived as brighter (or darker) via simultaneous brightness contrast (SBC), reaction times were significantly faster to a bright (or dark) annulus than to a dark (or bright) annulus. We further show that context-dependent brightness priming does not correlate with visibility using an objective measure of awareness (Experiment 1) and that context-dependent, but not context-independent brightness priming, occurs equally strongly for stimuli below or above the subjective threshold for awareness (Experiment 2). These results suggest that SBC occurs at early levels of visual input and is not influenced by conscious perception.     

Another look at semantic priming without awareness

In a recent study, McCauley, Parmelee, Sperber, and Carr (1980) reported results indicating that semantic priming had been produced by visual stimuli that were backward masked at durations too brief for greater than chance report. The conclusions drawn from such an experiment are critically dependent upon whether or not the primes were actually masked below the thresh-old for identification during priming trials. The three experiments reported here provide evidence that this requirement was not met. Rather, McCauley et al.’s (1980) methodology allowed for an uncontrolled increase in light adaptation during the actual testing of prime efficacy in the priming session. This increase in light adaptation reduced the effectiveness of the backward mask and resulted in an increase in prime visibility during priming trials. Thus, semantic priming probably occurred under conditions in which commensurate visual information was actually available.     

A position-sensitive Stroop effect: further evidence for a left-to-right component in print-to-speech conversion

In the classical Stroop effect, response times for naming the color in which a word is printed are affected by the presence of semantic, phonological, or orthographic relationships between the stimulus word and the response word. We show that color naming responses are faster when the printed word shares a phoneme with the color name to be produced than when it does not, in conditions where there is no semantic relationship between the printed word and the color name. This result is compatible with a variety of computational models of reading. However, we also found that these effects are much larger when it is the first phoneme that the stimulus and response share than when it is the last. Our data are incompatible with computational models of reading in which the computation of phonology from print is purely parallel. The dual route cascaded model computational model of reading, which has a lexical route that operates in parallel and a nonlexical route that operates serially letter by letter, successfully simulates this position-sensitive Stroop effect. The model also successfully simulates the “onset effect” in masked priming (Forster & Davis, 1991) and the interaction between the regularity effect and the position in a word of a grapheme-phoneme irregularity (Rastle & Coltheart, 1999b)-effects which, we argue, arise for the same reason as the position-sensitive Stroop effect we report.     

Attention capture without awareness in a non-spatial selection task

Distractors presented prior to a critical target in a rapid sequence of visually-presented items induce a lag-dependent deficit in target identification, particularly when the distractor shares a task-relevant feature of the target. Presumably, such capture of central attention is important for bringing a target into awareness. The results of the present investigation suggest that greater capture of attention by a distractor is not accompanied by greater awareness of it. Moreover, awareness tends to be limited to superficial characteristics of the target such as colour. The findings are interpreted within the context of a model that assumes sudden increases in arousal trigger selection of information for consolidation in working memory. In this conceptualization, prolonged analysis of distractor items sharing task-relevant features leads to larger target identification deficits (i.e., greater capture) but no increase in awareness.     

Semantic priming without awareness: Some methodological considerations and replications

Previous studies of subliminal semantic priming effects are considered. The distinction between subjective and objective detection thresholds proposed by Cheesman and Merikle (1984) is accepted, and it is concluded that no convincing evidence has been adduced to support or deny the existence of semantic priming effects at or below objective threshold. New criteria for the assessment of objective thresholds are proposed, and four experiments are reported in each of which pattern-masked primes were presented 10% below objective threshold. The first three experiments presented primes, mask, and targets binocularly; the fourth used dichoptic presentation. Data were analysed using both conventional F ratios and the quasi F ratio advocated by Clark (1973). Results showed that significant subliminal semantic priming effects occurred in each experiment when conventional F ratios were used, and significant effects occurred in all but the first experiment when quasi F was used. Binocular and dichoptic presentation of stimuli gave semantic priming effects whose magnitudes did not differ significantly. It is concluded that semantic priming effects can be obtained below objective detection threshold. It is also concluded that replication with different participants and different stimuli is preferable to the use of quasi F ratios in investigations where verbal stimuli are used.