Either or neither, but not both : locating the effects of masked primes

Execution of a response that has been primed by a backward-masked stimulus is inhibited (negative compatibility effect; NCE). Three experiments investigated the locus of this inhibition. Masked primes (left- or right-pointing arrows) were followed either by an arrow or a circle target. Arrow targets always required a left- or right-hand response, but the experiments differed in the response required to circles: press neither, either or both response keys (i.e. nogo, free choice and bimanual, respectively). Arrow targets showed the usual NCEs. Circle targets showed NCEs in the form of a response bias away from the primed response in the nogo and free-choice tasks; primes and targets differed on these trials, ruling out a perceptual explanation of the NCE. The bimanual task showed no such bias, suggesting that the NCE is located at a level of abstract response codes rather than specific muscle commands

The negative compatibility effect: A case for self-inhibition

In masked priming, a briefly presented prime stimulus is followed by a mask, which in turn is followed by the task-relevant target. Under certain conditions, negative compatibility effects (NCNCEs) occur, with impaired performance on compatible trials (where prime and target indicate the same response) relative to incompatible trials (where they indicate opposite responses). However, the exact boundary conditions of NCEs, and hence the functional significance of this effect, are still under discussion. In particular, it has been argued that the NCE might be a stimulus-specific phenomenon of little general interest. This paper presents new findings indicating that the NCE can be obtained under a wider variety of conditions, suggesting that it reflects more general processes in motor control. In addition, evidence is provided suggesting that prime identification levels in forced choice tasks – usually employed to estimate prime visibility in masked prime tasks – are affected by prior experience with the prime (Exp. 1) as well as by direct motor priming (Exp. 2 & 3)

The influence of the type of background noise on perceptual learning of speech in noise

Objectives: Auditory perceptual learning studies tend to focus on the nature of the target stimuli. However, features of the background noise can also have a significant impact on the amount of benefit that participants obtain from training. This study explores whether perceptual learning of speech in background babble noise generalizes to other, real-life environmental background noises (car and rain), and if the benefits are sustained over time. Design: Normal-hearing native English speakers were randomly assigned to a training (n = 12) or control group (n = 12). Both groups completed a pre- and post-test session in which they identified Bamford-Kowal-Bench (BKB) target words in babble, car, or rain noise. The training group completed speech-in-babble noise training on three consecutive days between the pre- and post-tests. A follow up session was conducted between 8 and 18 weeks after the post-test session (training group: n = 9; control group: n = 7). Results: Participants who received training had significantly higher post-test word identification accuracy than control participants for all three types of noise, although benefits were greatest for the babble noise condition and weaker for the car- and rain-noise conditions. Both training and control groups maintained their pre- to post-test improvement over a period of several weeks for speech in babble noise, but returned to pre-test accuracy for speech in car and rain noise. Conclusion: The findings show that training benefits can show some generalization from speech-in-babble noise to speech in other types of environmental noise. Both groups sustained their learning over a period of several weeks for speech-in-babble noise. As the control group received equal exposure to all three noise types, the sustained learning with babble noise, but not other noises, implies that a structural feature of babble noise was conducive to the sustained improvement. These findings emphasize the importance of considering the background noise as well as the target stimuli in auditory perceptual learning studies

The relationship between reversed masked priming and the tri-phasic pattern of the lateralised readiness potential.

One of the potential explanations for negative compatibility effects (NCE) in subliminal motor priming tasks has been perceptual prime-target interactions. Here, we investigate whether the characteristic tri-phasic LRP pattern associated with the NCE is caused by these prime-target interactions. We found that both the prime-related phase and the critical reversal phase remain present even on trials where the target is omitted, confirming they are elicited by the prime and mask, not by prime-target interactions. We also report that shape and size of the reversal phase are associated with response speed, consistent with a causal role for the reversal for the subsequent response latency. Additionally, we analysed sequential modulation of the NCE by previous conflicting events, even though such conflict is subliminal. In accordance with previous literature, this modulation is small but significant

Follow the sign! Top-down contingent attentional capture of masked arrow cues

Arrow cues and other overlearned spatial symbols automatically orient attention according to their spatial meaning. This renders them similar to exogenous cues that occur at stimulus location. Exogenous cues trigger shifts of attention even when they are presented subliminally. Here, we investigate to what extent the mechanisms underlying the orienting of attention by exogenous cues and by arrow cues are comparable by analyzing the effects of visible and masked arrow cues on attention. In Experiment 1, we presented arrow cues with overall 50% validity. Visible cues, but not masked cues, lead to shifts of attention. In Experiment 2, the arrow cues had an overall validity of 80%. Now both visible and masked arrows lead to shifts of attention. This is in line with findings that subliminal exogenous cues capture attention only in a top-down contingent manner, that is, when the cues fit the observer’s intentions

The Validity of d′ Measures

Subliminal perception occurs when prime stimuli that participants claim not to be aware of nevertheless influence subsequent processing of a target. This claim, however, critically depends on correct methods to assess prime awareness. Typically, d′ (“d prime”) tasks administered after a priming task are used to establish that people are unable to discriminate between different primes. Here, we show that such d′ tasks are influenced by the nature of the target, by attentional factors, and by the delay between stimulus presentation and response. Our results suggest that the standard d′ task is not a straightforward measure of prime visibility. We discuss the implications of our findings for subliminal perception research

When Your Decisions Are Not (Quite) Your Own: Action Observation Influences Free Choices

A growing number of studies have begun to assess how the actions of one individual are represented in an observer. Using a variant of an action observation paradigm, four experiments examined whether one person's behaviour can influence the subjective decisions and judgements of another. In Experiment 1, two observers sat adjacent to each other and took turns to freely select and reach to one of two locations. Results showed that participants were less likely to make a response to the same location as their partner. In three further experiments observers were asked to decide which of two familiar products they preferred or which of two faces were most attractive. Results showed that participants were less likely to choose the product or face occupying the location of their partner's previous reaching response. These findings suggest that action observation can influence a range of free choice preferences and decisions. Possible mechanisms through which this influence occurs are discussed

Age-related differences in selection by visual saliency

We examined the ability of older adults to select local and global stimuli varying in perceptual saliency – a task requiring non-spatial visual selection. Participants were asked to identify in separate blocks a target at either the global or local level of a hierarchical stimulus, while the saliency of each level was varied (across different conditions either the local or the global form was the more salient and relatively easier to identify). Older adults were less efficient than young adults in ignoring distractors that were higher in saliency than targets, and this occurred across both the global and local levels of form. The increased effects of distractor saliency on older adults occurred even when the effects were scaled by overall differences in task performance. The data provide evidence for an age-related decline in non spatial attentional selection of low-salient hierarchical stimuli, not determined by the (global or local) level at which selection was required. We discuss the implications of these results for understanding both the interaction between saliency and hierarchical processing and the effects of aging on non-spatial visual attention

Sensorimotor supremacy: Investigating conscious and unconscious vision by masked priming

According to the sensorimotor supremacy hypothesis, conscious perception draws on motor action. In the present report, we will sketch two lines of potential development in the field of masking research based on the sensorimotor supremacy hypothesis. In the first part of the report, evidence is reviewed that masked, invisible stimuli can affect motor responses, attention shifts, and semantic processes. After the review of the corresponding evidence – so-called masked priming effects – an approach based on the sensorimotor supremacy hypothesis is detailed as to how the question of a unitary mechanism of unconscious vision can be pursued by masked priming studies. In the second part of the report, different models and theories of backward masking and masked priming are reviewed. Types of models based on the sensorimotor hypothesis are discussed that can take into account ways in which sensorimotor processes (reflected in masked priming effects) can affect conscious vision under backward masking conditions

Centre–surround inhibition is a general aspect of famous-person recognition: evidence from negative semantic priming from clearly visible primes

A Centre-Surround Attentional Mechanism was proposed by Carr and Dagenbach (1990) to account for their observations of negative semantic priming from hard-to-perceive primes. The mechanism cannot account for the observation of negative semantic priming when primes are clearly visible. Three experiments (n = 30, 46, and 30) used a familiarity decision to names of famous people preceded by prime names of the same or different occupation. Negative semantic priming was observed at 150 or 200ms SOA with positive priming at shorter (50ms) and longer (1000ms) SOA. Experiment 3 verified that the primes were easily recognisable in the priming task at a SOA that yielded negative semantic priming, which cannot be predicted by the original Centre-Surround mechanism. A modified version is proposed that explains transiently negative semantic priming by proposing that Centre-Surround inhibition is a normal, automatically invoked aspect of the semantic processing of visually-presented famous names