A task-difficulty artifact in subliminal priming

Subliminal priming is said to occur when a subliminal prime influences the classification of a subsequent target. Most subliminal-priming claims are based on separate target- and prime-classification tasks. Because primes are intended to be subliminal, the prime-classification task is difficult, and the target-classification task is easy. To assess whether this task-difficulty difference accounts for previous claims of subliminal priming, we manipulated the ease of the prime-classification task by intermixing long-duration (visible) primes with short-duration (near liminal) ones. In Experiment 1, this strategy of intermixing long-duration primes raised classification of the shortduration ones. In Experiments 2 and 3, prime duration was lowered in such a way that prime classification was at chance in intermixed presentations. Under these conditions, we failed to observe any priming effects; hence, previous demonstrations of subliminal priming may simply have reflected a task-difficulty artifact.     

Conscious contributions to subliminal priming

Choice reaction times to visual stimuli (targets) may be influenced by preceding subliminal stimuli (primes). Some authors reported a straight priming effect i.e., responses were faster when primes and targets called for the same response than when they called for different responses. Others found the reversed pattern of results. Eimer and Schlaghecken [Eimer, M. & Schlaghecken, F. (2002). Links between conscious awareness and response inhibition: evidence from masked priming. Psychonomic Bulletin &Review, 9, 514-520.] showed recently that straight priming occurs whenever a prime is not efficiently masked thereby the information provided by the prime is accessible for consciousness. In the present study, a hypothesis is tested that straight priming is due to mediation of consciousness. To test this hypothesis, prime validity was manipulated. We showed that even when no mask was used so that participants could fully and consciously perceive the prime and participants were informed that primes were mostly invalid, for the short prime-target ISI interval (100 ms) straight priming occurred. The priming was inverse when the ISI was 800 ms. This indicates that participants were able to use the information provided by the prime to prepare the response opposite to that cued by the prime but only if the time between the prime and the target was long enough.     

Inhibition of return in subliminal letter priming

The present study combined exogenous spatial cueing with masked repetition priming to study attentional influences on the processing of subliminal stimuli. Participants performed an alphabetic decision task (letter versus pseudo-letter classification) with central targets and briefly presented peripherally located primes that were either cued or not cued by an abrupt onset. A relatively long delay between cue and prime was used to investigate the effect of inhibition of return (IOR) on the processing of subliminal masked primes. Primes presented to the left visual field showed standard effects of Cue Validity and no IOR (significant priming with valid cues only). Primes presented to the right visual field showed no priming from valid cues (an IOR effect), and priming with invalid cues that depended on hand of response to letter targets (right-hand in Experiment 1, left-hand in Experiment 2). The results are interpreted in terms of a differential speed of engagement and disengagement of attention to the right and left visual fields for alphabetic stimuli, coupled with a complex interaction that arises between Prime Relatedness and response-hand.     

Test-retest reliability of subliminal facial affective priming

Since the seminal 1993 demonstrations o f Murphy an d Zajonc, researchers have replicated and extended findings concerning subliminal affective priming. So far, however, no data on test-retest reliability of affective priming effects are available. A subliminal facial affective priming task was administered to 22 healthy individuals (15 women and 7 men) twice about 7 wk. apart. Happy and sad facial expressions were used as affective primes and neutral Chinese ideographs served as target masks, which had to be evaluated. Neutral facial primes and a no-face condition served as baselines. All participants reported not having seen any of the prime faces at either testing session. Priming scores for affective faces compared to the baselines were computed. Acceptable test-retest correlations (rs) of up to .74 were found for the affective priming scores. Although measured almost 2 mo. apart, subliminal affective priming seems to be a temporally stable effect.     

Perceptual learning can reverse subliminal priming effects

Masked primes presented prior to a target can result in inverse priming (i.e., benefits on trials in which the prime and the target are mapped onto opposite responses). In five experiments, time-of-task effects on subliminal priming of motor responses were investigated. First, we replicated Klapp and Hinkley's (2002) finding that the priming effect is initially straight (i.e., it benefits congruent trials, in which the prime and targets are mapped onto the same response) or absent, and only later reverses (i.e., faster responses in incongruent than in congruent trials). We show that the presentation of the mask plays a crucial role in this reversal and that the reversal occurs later if the mask pattern is very complex. We suggest that perceptual learning improves the recognition of task-relevant features. Once recognized, these features can trigger the preparation of the alternative response and/or inhibit the prime-activated response. These findings support an active role of the mask in priming.     

Exogenous spatial cueing modulates subliminal masked priming

An experiment combined exogenous spatial cueing with masked repetition priming. The task consisted of an alphabetic decision task (letter/pseudo-letter classification) with central targets and peripheral primes that were preceded by a valid or invalid spatial cue in the form of an exogenous abrupt onset. In an analysis including only participants who were not aware of prime stimuli, exogenous location cueing was found to reliably modulate the size of unconscious priming effects. These findings suggest that in early vision the exogenous cue boosts the signal at the location of the cue resulting in a higher gain for the subliminal prime. Our findings therefore suggest that exogenous cueing can affect the first feedforward sweep of information through the brain, a processing stream which is considered to be automatic and unconscious.     

The effect of subliminal priming on sleep duration

Two experiments primed college students with either sleep‐related or neutral words and then assessed sleep during a 25 minute nap period. Both experiments showed that participants primed with sleep‐related words reported having slept longer than did those primed with neutral words. Furthermore, both experiments showed that sleep‐primed participants exhibited lower heart rate. Experiment 2 also revealed that the effect of the priming manipulation was especially strong among participants who had trouble sleeping. This suggests that priming might be a cost‐effective treatment for inducing sleep among people with sleep problems.     

Response priming by supraliminal and subliminal action effects

Theories assuming an effect-based coding of action predict that motor responses become activated by the perception of the responses' sensory effects. In accordance with this prediction it was found that responding to a visual target is faster and more accurate when the target is briefly preceded by the visual effect of the required response. Most importantly, this effect-induced response priming was independent of prime perceptibility and it occurred even when the prime was not consciously discriminable. Beyond ruling out alternative interpretations of earlier induction studies in terms of deliberate response biases, this suggests that effect codes evoke their associated motor patterns in a highly automatic manner not affording conscious mediation. The results accord with a functional dissociation between the consciousness-mediated implementation and the consciousness-independent realization of action goals.     

A neural network model of inhibitory processes in subliminal priming

Masked priming experiments have revealed a precise set of facilitatory and inhibitory visuomotor control processes. Most notably, inhibitory effects have been identified in which prime-target compatibility induces performance costs and prime-target incompatibility induces performance benefits. We argue that this profile of data is commensurate with an “emergency braking mechanism”, whereby responses can be retracted as a result of changing sensory evidence. The main contribution of this paper is to provide a neural network-based explanation of this phenomenon. This is obtained through the use of feedforward inhibition to implement backward masking, lateral inhibition to implement response competition, and opponent processing mechanisms to implement response retraction. Although the model remains simple, it does a very good job of reproducing the available masked priming data. For example, it reproduces a large spectrum of reaction time data across a number of different experimental conditions. Perhaps most notably, however, it also reproduces lateralized readiness potentials that have been recorded while subjects perform different conditions. In addition, it provides a concrete set of testable predictions.     

阈下情绪启动对认知任务转换的影响

阈下情绪启动是最近热点问题之一。本研究通过两个实验考察了阈上和阈下情绪图片所诱发的情绪状态对任务转换的影响。实验一对28名被试分别阈上启动三种情绪,发现积极和消极情绪对任务转换有一定的影响,但积极情绪与消极情绪两者对任务转换影响的差异不显著。实验二对32名被试分别阈下启动三种情绪,并完成相应的数字任务,发现三种情绪下的转换损失无显著性差异。以上结果表明阈上和阈下刺激所诱发的情绪对任务转换影响机制是有差异的。     

Long-lasting effects of subliminal affective priming from facial expressions

Unconscious processing of stimuli with emotional content can bias affective judgments. Is this subliminal affective priming merely a transient phenomenon manifested in fleeting perceptual changes, or are long-lasting effects also induced? To address this question, we investigated memory for surprise faces 24 h after they had been shown with 30-ms fearful, happy, or neutral faces. Surprise faces subliminally primed by happy faces were initially rated as more positive, and were later remembered better, than those primed by fearful or neutral faces. Participants likely to have processed primes supraliminally did not respond differentially as a function of expression. These results converge with findings showing memory advantages with happy expressions, though here the expressions were displayed on the face of a different person, perceived subliminally, and not present at test. We conclude that behavioral biases induced by masked emotional expressions are not ephemeral, but rather can last at least 24 h.     

Modularity in musical processing: the automaticity of harmonic priming

Three experiments investigated the modularity of harmonic expectations that are based on cultural schemata despite the availability of more predictive veridical information. Participants were presented with prime-target chord pairs and made an intonation judgment about each target. Schematic expectation was manipulated by the combination of prime and target, with some transitions being schematically more probable than others. Veridical information in the form of prime-target previews, local transition probabilities, or valid versus invalid previews was also provided. Processing was facilitated when a schematically probable target chord followed the prime. Furthermore, this effect was independent of all manipulations of veridical expectation. A solution to L. B. Meyer's (1967b) query "On Rehearing Music" is suggested, in which schematic knowledge contributes to harmonic expectation in a modular manner regardless of whether any veridical knowledge exists.     

Interaction of prime and target in the subliminal affective priming effect

It has been found that an emotional stimulus such as a facial expression presented subliminally can affect subsequent information processing and behavior, usually by shifting evaluation of a subsequent stimulus to a valence congruent with the previous stimulus. This phenomenon is called subliminal affective priming. The present study was conducted to replicate and expand previous findings by investigating interaction of primes and targets in the affective priming effect. Two conditions were used. Prime (subliminal presentation 35 msec.) of an angry face of a woman and a No Prime control condition. Just after presentation of the prime, an ambiguous angry face or an emotionally neutral face was presented above the threshold of awareness (500 msec.). 12 female undergraduate women judged categories of facial expressions (Anger, Neutral, or Happiness) for the target faces. Analysis indicated that the Anger primes significantly facilitated judgment of anger for the ambiguous angry faces; however, the priming effect of the Anger primes was not observed for neutral faces. Consequently, the present finding suggested that a subliminal affective priming effect should be more prominent when affective valence of primes and targets is congruent.     

Differential priming effect for subliminal fear and disgust facial expressions

Compared to neutral or happy stimuli, subliminal fear stimuli are known to be well processed through the automatic pathway. We tried to examine whether fear stimuli could be processed more strongly than other negative emotional stimuli using a modified subliminal affective priming paradigm. Twenty-six healthy subjects participated in two separated sessions. Fear, disgust and neutral facial expressions were adopted as primes, and 50% happy facial stimuli were adopted as a target to let only stronger negative primes reveal a priming effect. Participants were asked to appraise the affect of target faces in the affect appraisal session and to appraise the genuineness of target faces in the genuineness appraisal session. The genuineness instruction was developed to help participants be sensitive to potential threats. In the affect appraisal, participants judged 50% happy target faces significantly more 'unpleasant' when they were primed by fear faces than primed by 50% happy control faces. In the genuineness appraisal, participants judged targets significantly more 'not genuine' when they were primed by fear and disgust faces than primed by controls. These findings suggest that there may be differential priming effects between subliminal fear and disgust expressions, which could be modulated by a sensitive context of potential threat.     

Response readiness modulates the development of association-based automaticity in masked priming

The current study investigated the role of the automatization of stimulus and response (S-R) associations and response readiness in triggering the motor activation for masked primes in two experiments. The automatization of associations was manipulated by employing different types of stimuli, and response readiness was manipulated by varying the relative frequency of Go trials in a modified Go/No-Go task. Compatibility (compatible and incompatible), stimulus type (arrows and parallel lines), and test session (Sessions 1, 2, and 3) were manipulated in a high response-readiness condition (Experiment 1) and in a low response-readiness condition (Experiment 2). Negative compatibility effects (NCEs) occurred regardless of session and experiment in the arrow stimuli condition. However, in the parallel-line stimuli condition, no significant compatibility effect (CE) appeared regardless of the experiment in Sessions 1 and 2, whereas a significant NCE appeared in Experiment 1 but not in Experiment 2 in Session 3. These results are consistent with the claim that motor activation can only occur if the association between specific stimuli and specific responses has been automatized by previous practice, and response readiness can modulate the development of automaticity, but this modulation will have a minimal effect once the association is automatized. The findings also provide experimental evidence for the assumption that the formation of association-based automaticity could be modulated by top-down control (e.g., response readiness).     

No evidence for subliminal affective priming with emotional facial expression primes

The present study investigated whether facial expressions of emotion presented outside consciousness awareness will elicit evaluative responses as assessed in affective priming. Participants were asked to evaluate pleasant and unpleasant target words that were preceded by masked or unmasked schematic (Experiment 1) or photographic faces (Experiments 1 and 2) with happy or angry expressions. They were either required to perform the target evaluation only or to perform the target evaluation and to name the emotion expressed by the face prime. Prime-target interval was 300 ms in Experiment 1 and 80 ms in Experiment 2. Naming performance confirmed the effectiveness of the masking procedure. Affective priming was evident after unmasked primes in tasks that required naming of the facial expressions for schematic and photographic faces and after unmasked primes in tasks that did not require naming for photographic faces. No affective priming was found after masked primes. The present study failed to provide evidence for affective priming with masked face primes, however, it indicates that voluntary attention to the primes enhances affective priming.     

Attention and automaticity in Stroop and priming tasks: Theory and data

Three major variables identified with attention and automaticity in the priming paradigm are shown to have parallel effects in the Stroop paradigm. A model is developed to explain the effects in both paradigms in terms of a single decision process that combines evidence from several sources (e.g., habitual associations and temporary contingencies between the prime and the target or between the unreported and reported dimensions). The model is applied to two Stroop experiments in which the faster two of three stimulus dimensions relate associatively and cue through a frequency manipulation the third, which must be reported. Depending on the direction of the cueing relation, attentional effects enhanced or counteracted automatic (associative) effects, and the attentional effects were stronger with the faster unreported dimension than with the slower one. These results corroborate findings in the priming paradigm and confirm the model. Implications of the results and the model for broader issues are discussed.     

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.     

Detecting chance: A solution to the null sensitivity problem in subliminal priming

In many paradigms, the persuasiveness of subliminal priming relies on establishing that stimuli are undetectable. The standard significance test approach is ill-suited as null results may reflect either truly undetectable stimuli or a lack of power to resolve weakly detectable stimuli. We present a novel statistical model as an alternative. The model provides for estimates of the probability that each individual is truly at chance. Researchers may select individuals for whom there are sufficiently high probabilities of true undetectability. The model is hierarchical, and estimation is done within the Bayesian framework.     

Limited transfer of subliminal response priming to novel stimulus orientations and identities

Recently, priming effects of unconscious stimuli that were never presented as targets have been taken as evidence for the processing of the stimuli's semantic categories. The present study explored the necessary conditions for a transfer of priming to novel primes. Stimuli were digits and letters which were presented in various viewer-related orientations (upright, horizontal, inverted). The transfer of priming to novel stimulus orientations and identities was remarkably limited: in Experiment 1, in which all conscious targets stood upright, no transfer to unconscious primes in a non-target orientation was found. Experiment 2, in which primes were presented without masks, ruled out the possibility that primes were presented too short to allow congruency effects. In Experiments 3 and 4, in which all targets were presented upside down, priming transferred to upright stimuli with target identities but neither to horizontal stimuli nor to stimuli with novel identities. We suggest that whether a transfer of priming to unpracticed stimuli occurs or not depends on observers' expectations of specific stimulus exemplars.