Inhibition and decay of motor and nonmotor priming

Motor responses can be facilitated by congruent visual stimuli and prolonged by incongruent visual stimuli that are made invisible by masking (direct motor priming). Recent studies on direct motor priming showed a reversal of these priming effects when a three-stimulus paradigm was used in which a prime was followed by a mask and a target stimulus was presented after a delay. A similar three-stimulus paradigm on nonmotor priming, however, showed no reversal of priming effects when the mask was used as a cue for processing of the following target stimulus (cue priming). Experiment 1 showed that the time interval between mask and target is crucial for the reversal of priming. Therefore, the time interval between mask and target was varied in three experiments to see whether cue priming is also subject to inhibition at a certain time interval. Cues indicated (1) the stimulus modality of the target stimulus, (2) the task to be performed on a multidimensional auditory stimulus, or (3) part of the motor response. Whereas direct motor priming showed the reversal of priming about 100 msec after mask presentation, cue priming effects simply decayed during the 300 msec after mask presentation. These findings provide boundary conditions for accounts of inverse priming effects.     

PRP-paradigm provides evidence for a perceptual origin of the negative compatibility effect

Visual stimuli (primes) that are made invisible by masking can affect motor responses to a subsequent target stimulus. When a prime is followed by a mask which is followed by a target stimulus, an inverse priming effect (or negative compatibility effect) has been found: Responses are slow and frequently incorrect when prime and target stimuli are congruent, but fast and accurate when prime and target stimuli are incongruent. To functionally localize the origins of inverse priming effects, we applied the psychological refractory period (PRP-) paradigm which distinguishes a perceptual level, a central bottleneck, and a level of motor execution. Two dual-task experiments were run with the PRP-paradigm to localize the inverse priming effect relative to the central bottleneck. Together, results of the Effect-Absorption and the Effect-Propagation Procedure suggest that inverse priming effects are generated by perceptual mechanisms. We suggest two perceptual mechanisms as the source of inverse priming effects.     

Inverse target- and cue-priming effects of masked stimuli

The processing of a visual target that follows a briefly presented prime stimulus can be facilitated if prime and target stimuli are similar. In contrast to these positive priming effects, inverse priming effects (or negative compatibility effects) have been found when a mask follows prime stimuli before the target stimulus is presented: Responses are facilitated after dissimilar primes. Previous studies on inverse priming effects examined target-priming effects, which arise when the prime and the target stimuli share features that are critical for the response decision. In contrast, 3 experiments of the present study demonstrate inverse priming effects in a nonmotor cue-priming paradigm. Inverse cue-priming effects exhibited time courses comparable to inverse target-priming effects. Results suggest that inverse priming effects do not arise from specific processes of the response system but follow from operations that are more general.     

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.     

Backward affective priming: Even when the prime is late, people still evaluate

It is well-established that affective stimuli can prime congruent evaluations if they precede the target within a short time interval, i.e., forward affective priming. The present research examines whether similar effects occur if affective primes succeed target presentation, i.e., backward affective priming. Experiments 1 found short-lived, yet reliable backward affective priming. Experiment 2 found parallel forward affective priming in the same paradigm. Experiment 3 found forward and backward affective priming in a within-subjects design. Comparison with neutral primes suggested that the observed effects were mainly due to interference. Backward affective priming is a robust phenomenon that may reflect a rapid and continuous evaluation of environmental stimuli.     

Visual similarity effects on masked priming

We investigated the role of the visual similarity of masked primes to targets in a lexical decision experiment. In the primes, some letters in the target (e.g., A in ABANDON) had either visually similar letters (e.g., H), dissimilar letters (D), visually similar digits (4), or dissimilar digits (6) substituted for them. The similarities of the digits and letters to the base letter were equated and verified in a two-alternative forced choice (2AFC) perceptual identification task. Using targets presented in lowercase (e.g., abandon) and primes presented in uppercase, visually similar digit primes (e.g., 484NDON) produced more priming than did visually dissimilar digit primes (676NDON), but little difference was found between the visually similar and dissimilar letter primes (HRHNDON vs. DWDNDON). These results were explained in terms of task-driven competition between the target letter and the visually similar letter.     

Perceptual latency priming by masked and unmasked stimuli: evidence for an attentional interpretation

Four experiments investigated the influence of a metacontrast-masked prime on temporal order judgments. The main results were (1) that a masked prime reduced the latency of the mask's conscious perception (perceptual latency priming), (2) that this effect was independent of whether the prime suffered strong or weak masking, (3) that it was unaffected by the degree of visual similarity between the prime and the mask, and that (4) there was no difference between congruent and incongruent primes. Finding (1) suggests that location cueing affects not only response times but also the latency of conscious perception. (2) The finding that priming was unaffected by the prime's detectability argues against a response bias interpretation of this effect. (3) Since visual similarity had no effect on the prime's efficiency, it is unlikely that sensory priming was involved. (4) The lack of a divergence between the effects of congruent and incongruent primes implies a functional difference between the judgments in the temporal order judgment task and speeded responses that have demonstrated differential effects of congruent and incongruent primes (e.g., Klotz & Neumann, 1999). These results can best be interpreted by assuming that the prime affects perceptual latency by initiating a shift of attention, as suggested by the Asynchronous Updating Model (AUM; Neumann 1978, 1982).     

The perceptual nature of audiovisual interactions for semantic knowledge in young and elderly adults

Audiovisual interactions for familiar objects are at the core of perception. The nature of these interactions depends on the amodal – sensory abstracted – or modal – sensory-dependent – approach of knowledge. According to these approaches, the interactions should be respectively semantic and indirect or perceptual and direct. This issue is therefore a central question to memory and perception, yet the nature of these interactions remains unexplored in young and elderly adults. We used a cross-modal priming paradigm combined with a visual masking procedure of half of the auditory primes. The data demonstrated similar results in the young and elderly adult groups. The mask interfered with the priming effect in the semantically congruent condition, whereas the mask facilitated the processing of the visual target in the semantically incongruent condition. These findings indicate that audiovisual interactions are perceptual, and support the grounded cognition theory.     

Masked stimuli modulate endogenous shifts of spatial attention

Unconscious stimuli can influence participants’ motor behavior but also more complex mental processes. Recent research has gradually extended the limits of effects of unconscious stimuli. One field of research where such limits have been proposed is spatial cueing, where exogenous automatic shifts of attention have been distinguished from endogenous controlled processes which govern voluntary shifts of attention. Previous evidence suggests unconscious effects on mechanisms of exogenous shifts of attention. Here, we applied a cue-priming paradigm to a spatial cueing task with arbitrary cues by centrally presenting a masked symmetrical prime before every cue stimulus. We found priming effects on response times in target discrimination tasks with the typical dynamic of cue-priming effects (Experiments 1 and 2) indicating that central symmetrical stimuli which have been associated with endogenous orienting can modulate shifts of spatial attention even when they are masked. Prime–Cue Congruency effects of perceptual dissimilar prime and cue stimuli (Experiment 3) suggest that these effects cannot be entirely reduced to perceptual repetition priming of cue processing. In addition, priming effects did not differ between participants with good and poor prime recognition performance consistent with the view that unconscious stimulus features have access to processes of endogenous shifts of attention.     

A PRP-study to determine the locus of target priming effects

Visual stimuli that are made invisible by a following mask can nonetheless affect motor responses. To localize the origin of these target priming effects we used the psychological refractory period paradigm. Participants classified tones as high or low, and responded to the position of a visual target that was preceded by a prime. The stimulus onset asynchrony (SOA) between both tasks varied. In Experiment 1 the tone task was followed by the position task and SOA dependent target priming effects were observed. When the visual position task preceded the tone task in Experiment 2, with short SOA the priming effect propagated entirely to the tone task yielding faster responses to tones on visually congruent trials and delayed responses to tones on visually incongruent trials. Together, results suggest that target priming effects arise from processing before and at the level of the central bottleneck such as sensory analysis and response selection.     

Best face forward: Similarity effects in repetition priming of face recognition

Two experiments examined the graded similarity effect in the repetition priming of familiar face recognition. From the model of repetition priming proposed by Burton, Bruce, and Johnston (1990) it was predicted that similarity effects may be a confound of stimulus preparation. Experiment 1 was used to discount this hypothesis, but failed to replicate a pattern of graded priming related to the similarity of prime and target faces. Experiment 2 attempted a more extensive investigation using two different measures of prime-target similarity. The results replicated Ellis, Young, Flude, and Hay's (1987) finding that similar primes confer more priming than dissimilar ones, but found no correlation between amount of priming and the degree of prime-target resemblance for either similarity metric used. In view of these findings the mechanism of repetition priming in familiar face recognition is discussed.     

Inverse cue priming is not limited to masks with relevant features

Apart from positive priming effects, masked prime stimuli can impair responses to a subsequent target stimulus which shares response-critical features in contrast to a target assigned to the opposite response. This counterintuitive phenomenon is called inverse priming (or negative compatibility effect). Here we examine the generality of this phenomenon beyond priming of motor responses. We used a non-motor cue-priming paradigm to study the underlying mechanism of inverse priming for relevant features masks which include task-relevant stimulus features and for irrelevant masks which omit task-relevant features. We found inverse cue-priming effects with both types of masks. With task-irrelevant masks inverse cue-priming was emphasized in those participants being unable to perceive the prime. The existence of inverse non-motor priming under conditions where simple perceptual interactions between the stimuli are ruled out as the source of inverse priming is at odds with the view that inverse priming reflects motor inhibition. Alternatives are discussed.     

On the source and scope of priming effects of masked stimuli on endogenous shifts of spatial attention

Unconscious stimuli can influence participants’ motor behavior as well as more complex mental processes. Previous cue-priming experiments demonstrated that masked cues can modulate endogenous shifts of spatial attention as measured by choice reaction time tasks. Here, we applied a signal detection task with masked luminance targets to determine the source and the scope of effects of masked stimuli. Target-detection performance was modulated by prime-cue congruency, indicating that prime-cue congruency modulates signal enhancement at early levels of target processing. These effects, however, were only found when the prime was perceptually similar to the cue indicting that primes influence early target processing in an indirect way by facilitating cue processing. Together with previous research we conclude that masked stimuli can modulate perceptual and post-central levels of processing. Findings mark a new limit of the effects of unconscious stimuli which seem to have a smaller scope than conscious stimuli.     

Automatic letter priming in an alphabetic decision task

An alphabetic decision task was used to study effects of form priming on letter recognition at very short prime durations (20 to 80 msec). The task required subjects to decide whether a stimulus was a letter or a nonletter. Experiment 1 showed clear facilitatory effects of primes being either physically or nominally identical to the targets, with a stable advantage for the former. Experiment 2 demonstrated that uppercase letters are classified more rapidly as letters (vs. non-letters) when they are preceded by a briefly exposed, forward- and backward-masked, visually similar uppercase letter than when they are preceded by a visually dissimilar uppercase letter. Finally, Experiment 3 demonstrated that nominally identical and visually similar primes facilitate processing more than do nominally identical, visually dissimilar primes. The alphabetic decision task proved to produce sensitive and stable priming effects at the feature, letter, and response-choice level. The present results on letter-letter priming thus constitute a solid data base against which to evaluate other priming effects, such as word-letter priming. The results are discussed in light of current activation models of letter and word recognition and are compared with data simulated by the interactive activation model (McClelland & Rumelhart, 1981).     

A central-peripheral asymmetry in masked priming

Masked primes presented prior to a target result in behavioral benefits on incompatible trials (in which the prime and the target are mapped onto opposite responses) when they appear at fixation, but in behavioral benefits on compatible trials (in which the prime and the target are mapped onto the same response) when appearing peripherally. In Experiment 1, the time course of this central-peripheral asymmetry (CPA) was investigated. For central primes, compatible-trial benefits at short stimulus onset asynchronies (SOAs) turned into incompatible-trial benefits at longer SOAs. For peripheral primes, compatible-trial benefits at short SOAs increased in size with longer SOAs. Experiment 2 showed that these effects also occur when primes and targets are physically dissimilar, ruling out an interpretation in terms of the perceptual properties of the stimulus material. In Experiments 3 and 4, the question was investigated as to whether the CPA is related to visual-spatial attention and/or retinal eccentricity per se. The results indicate that the CPA is independent of attentional factors but strongly related to the physiological inhomogeneity of the retina. It is argued that central and peripheral primes trigger an initial motor activation, which is inhibited only if primes are presented at retinal locations of sufficiently high perceptual sensitivity. The results are discussed in terms of an activation threshold model.     

Trait Anxiety and Fear Responses to Safety Cues: Stimulus Generalization or Sensitization?

Abnormal fear responding to threat cues may contribute to the aetiology and maintenance of persistent fears and pathological anxiety. Chronic anxiety may also involve abnormal fear responding to ??safety?? cues, which do not signal danger. Yet investigations of fear responding to acquired safety cues are scarce and the basis of such responding remains unclear. Moreover, previous studies do not distinguish between stimulus generalization (an associative mechanism based on perceptual similarity between threat and safety cues) and sensitization (a non-associative mechanism whereby fear responses to any novel, intense, or fear-related stimulus are temporarily elevated). This study investigated responses to acquired safety cues in volunteers with varying trait anxiety, using a novel fear conditioning paradigm designed to distinguish between effects of trait anxiety on generalization and sensitization. The paradigm used three conditioned stimuli: a threat cue (CS+) and two safety cues (CS?), one perceptually similar to the CS+ and one perceptually dissimilar. Conditioned fear to these cues was indexed by fear potentiation of the startle blink reflex, skin conductance responses, and self-report. To examine how trait anxiety moderated responses to safety cues, participants were divided into high and low trait anxiety subgroups. Startle, skin conductance, and self-reported fear measures indicated that generalization of fear occurred for the safety cue which resembled the threat cue, but not for the perceptually dissimilar safety cue, consistent with the stimulus generalization hypothesis. There was some evidence that stimulus generalization was exaggerated in anxious individuals. The current study sheds light on the mechanism by which fear responses to safety cues arise in healthy individuals, and offers some insight into the influence of this mechanism in chronic anxiety.     

Phonological priming in the lexical decision task: A failure to replicate

Some models of the lexicon predict that recognition of words should produce activation spreading to phonologically related words. Consistent with this prediction, Hillinger (1980) demonstrated priming in a visual lexical decision task for word targets preceded by graphemically similar or graphemically dissimilar primes that rhymed with the target. In Experiment 1, we investigated whether this phonological priming effect occurred automatically or because of subject strategies. Although semantically associated primes produced significant facilitation in Experiment 1, no evidence of phonological priming was obtained. Experiments 2 to 5 were conducted in an attempt to obtain the phonological priming effect. Experiment 5 was a replication of one of Hillinger’s experiments. In none of these experiments was phonological priming observed. These results indicate either that the lexicon is not organized such that spreading activation occurs on the basis of phonological similarity, or that visual lexical decisions are made without phonological mediation.     

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.     

Unconscious and conscious priming by forms and their parts

Using metacontrast masking techniques, in two experiments we compare unconscious and conscious response priming by targets consisting of either whole forms or else their parts. In Experiment 1 we investigate the contribution of whole forms and their figural primitives, viz., edges and corners, to the unconscious priming effect. As expected, choice RTs were fast when the invisible target and visible mask shape pairings were congruent and slower when they were incongruent. This trend, while strongest for whole-targets, also held for the target primes composed only of corners but did not hold for target primes composed only of sides. Experiment 2 showed, replicating the results of Experiment 1, that while invisible corner targets produced weaker priming effects than invisible whole targets, paradoxically visible corner target produced stronger priming effects than visible whole targets. Taken together the results of the two experiments indicate (a) that unconscious target representations and, thus, unconscious priming effects are strongest when the target is a complete rather than a partial configuration, (b) that conjunctions of line or edge orientations forming corners produce stronger unconscious target representations and priming effects than do unconscious target representations formed from nonconjoined edge or line primitives, (c) that metacontrast masking of form occurs at or beyond levels of visual processing at which feature integration of visual form primitives occurs, and (d) that, when consciously perceived, partial forms can act as stronger primes than whole forms.     

Masked repetition and phonological priming within and across modalities

Lexical decision latencies to word targets presented either visually or auditorily were faster when directly preceded by a briefly presented (53-ms) pattern-masked visual prime that was the same word as the target (repetition primes), compared with different word primes. Primes that were pseudohomophones of target words did not significantly influence target processing compared with unrelated primes (Experiments 1-2) but did produce robust priming effects with slightly longer prime exposures (67 ms) in Experiment 3. Like repetition priming, these pseudohomophone priming effects did not interact with target modality. Experiments 4 and 5 replicated this general pattern of effects while introducing a different measure of prime visibility and an orthographic priming condition. Results are interpreted within the framework of a bimodal interactive activation model.