Revisiting the metacontrast dissociation: comparing sensitivity across different measures and tasks

In the metacontrast dissociation procedure, presenting a masked shape prime prior to a visible shape target leads to reaction-time effects of the prime in an indirect measure, although participants cannot consciously detect prime shapes in a direct measure (Klotz & Neumann, 1999). This has been taken as evidence for the processing of unconscious input. The results of the present metacontrast dissociation study indicate that although participants are unable to consciously report the shape of the prime, they can consciously perceive motion between masked primes and visible targets in a hybrid direct/indirect measure (Experiments 1 and 3). This indicates that former tests did not provide an exhaustive measure for residual conscious perception of the prime in the metacontrast dissociation procedure. Further tests, however, reveal that residual motion perception cannot account for performance in the indirect measure (Experiments 2 and 3). Although the results thus leave the conception of processing of unconscious input intact, they may prompt a revision of its criteria.     

Subliminal Gestalt grouping: Evidence of perceptual grouping by proximity and similarity in absence of conscious perception

Previous studies making use of indirect processing measures have shown that perceptual grouping can occur outside the focus of attention. However, no previous study has examined the possibility of subliminal processing of perceptual grouping. The present work steps forward in the study of perceptual organization, reporting direct evidence of subliminal processing of Gestalt patterns. In two masked priming experiments, Gestalt patterns grouped by proximity or similarity that induced either a horizontal or vertical global orientation of the stimuli were presented as masked primes and followed by visible targets that could be congruent or incongruent with the orientation of the primes. The results showed a reliable priming effect in the complete absence of prime awareness for both proximity and similarity grouping principles. These findings suggest that a phenomenal report of the Gestalt pattern is not mandatory to observe an effect on the response based on the global properties of Gestalt stimuli.     

Highly correlated stimuli do not necessarily facilitate the measurement of unconscious perception: Exclusion failure is hard to find in forced-choice tasks

Persaud and McLeod (2008) report that unconscious perception is easier to measure with forced-choice exclusion tasks when the stimuli are highly similar, such as choosing between the letters ‘h’ and ‘b’. The high degree of stimulus similarity may decrease conscious awareness of the target stimuli while leaving unconscious cognition intact. The present experiments used forced-choice exclusion tasks (i.e., choosing the opposite of a masked target stimulus) with the aim of replicating these findings. No evidence of relevant perception – either conscious or unconscious – was obtained with short duration targets. The forced-choice exclusion task was correctly performed at longer target durations (25 ms and higher), which suggests conscious perception of the target stimuli. We conclude that increasing stimulus similarity does not reliably produce exclusion failure effects and does not appear to facilitate the measurement of unconscious cognition.     

Evidence of fast and automatic gender bias in affective priming

Previous studies have revealed a gender bias in ratings of the valence and intensity of supraliminally presented facial expressions of emotion such that positive emotions receive higher ratings when expressed by females and negative emotions receive higher ratings when expressed by males. However, surprisingly, this gender bias has not been investigated for suboptimal presentation of emotional expressions. Our first experiment aimed at investigating the existence of such a bias for very fast presentation of the stimulus (20 ms onset) on the basis of a classic priming procedure commonly used in affective priming studies that involved the use of a single prime. Our second experiment aimed at proposing a new method involving four fast, repeated presentations of the prime-target pairs (based on the innovative design proposed by Höschel and Irle), that could be used to reduce the gender bias in future studies in affective sciences. Results show that the classic procedure for subliminal affective priming seems, indeed, sensitive to gender bias, but that it is possible to maximise the affective effect and decrease the impact of the gender bias using repeated presentations of the prime.     

Independence between implicit and explicit processing as revealed by the Simon effect

Studies showing human behavior influenced by subliminal stimuli mainly focus on implicit processing per se, and little is known about its interaction with explicit processing. We examined this by using the Simon effect, wherein a task-irrelevant spatial distracter interferes with lateralized response. Lo and Yeh (2008) found that the visual Simon effect, although it occurred when participants were aware of the visual distracters, did not occur with subliminal visual distracters. We used the same paradigm and examined whether subliminal and supra-threshold stimuli are processed independently by adding a supra-threshold auditory distracter to ascertain whether it would interact with the subliminal visual distracter. Results showed auditory Simon effect, but there was still no visual Simon effect, indicating that supra-threshold and subliminal stimuli are processed separately in independent streams. In contrast to the traditional view that implicit processing precedes explicit processing, our results suggest that they operate independently in a parallel fashion.     

Establishing object correspondence across eye movements: Flexible use of spatiotemporal and surface feature information

Visual input is frequently disrupted by eye movements, blinks, and occlusion. The visual system must be able to establish correspondence between objects visible before and after a disruption. Current theories hold that correspondence is established solely on the basis of spatiotemporal information, with no contribution from surface features. In five experiments, we tested the relative contributions of spatiotemporal and surface feature information in establishing object correspondence across saccades. Participants generated a saccade to one of two objects, and the objects were shifted during the saccade so that the eyes landed between them, requiring a corrective saccade to fixate the target. To correct gaze to the appropriate object, correspondence must be established between the remembered saccade target and the target visible after the saccade. Target position and surface feature consistency were manipulated. Contrary to existing theories, surface features and spatiotemporal information both contributed to object correspondence, and the relative weighting of the two sources of information was governed by the demands of the task. These data argue against a special role for spatiotemporal information in object correspondence, indicating instead that the visual system can flexibly use multiple sources of relevant information.     

Human and machine perception of biological motion

More than 30 years ago, Johansson was the first to show that humans are capable of recovering information about the identity and activity of animate creatures rapidly and reliably from very sparse visual inputs – the phenomenon of biological motion. He filmed human actors in a dark setting with just a few strategic points on the body marked by lights – so-called moving light displays (MLDs). Subjects viewing the MLDs reported a vivid impression of moving human forms, and were even able to tell the activity in which the perceived humans were engaged. Subsequently, the phenomenon has been widely studied and many attempts have been made to model and to understand it. Typical questions that arise are: How precisely is the sparse low-level information integrated over space and time to produce the global percept, and how important is world knowledge (e.g., about animal form, locomotion, gravity, etc.)? In an attempt to answer such questions, we have implemented a machine-perception model of biological motion. If the computational model can replicate human data then it might offer clues as to how humans achieve the task. In particular, if it can do so with no or minimal world knowledge then this knowledge cannot be essential to the perception of biological motion. To provide human data for training and against which to assess the model, an extensive psychophysical experiment was undertaken in which 93 subjects were shown 12 categories of MLDs (e.g., normal, walking backwards, inverted, random dots, etc.) and were asked to indicate the presence or absence of natural human motion. Machine perception models were then trained on normal sequences as positive data and random sequences as negative data. Two models were used: a k-nearest neighbour (k-NN) classifier as an exemplar of ‘lazy’ learning and a back-propagation neural network as an exemplar of ‘eager’ learning. We find that the k-NN classifier is better able to model the human data but it still fails to represent aspects of knowledge about body shape (especially how relative joint positions change under rotation) that appear to be important to human judgements.     

Visual working memory capacity for objects from different categories: a face-specific maintenance effect

The capacity of visual working memory was examined when complex objects from different categories were remembered. Previous studies have not examined how visual similarity affects object memory, though it has long been known that similar-sounding phonological information interferes with rehearsal in auditory working memory. Here, experiments required memory for two or four objects. Memory capacity was compared between remembering four objects from a single object category to remembering four objects from two different categories. Two-category sets led to increased memory capacity only when upright faces were included. Capacity for face-only sets never exceeded their nonface counterparts, and the advantage for two-category sets when faces were one of the categories disappeared when inverted faces were used. These results suggest that two-category sets which include faces are advantaged in working memory but that faces alone do not lead to a memory capacity advantage.     

Comparing performance in discrete and continuous comparison tasks

The approximate number system (ANS) theory suggests that all magnitudes, discrete (i.e., number of items) or continuous (i.e., size, density, etc.), are processed by a shared system and comply with Weber's law. The current study reexamined this notion by comparing performance in discrete (comparing numerosities of dot arrays) and continuous (comparisons of area of squares) tasks. We found that: (a) threshold of discrimination was higher for continuous than for discrete comparisons; (b) while performance in the discrete task complied with Weber's law, performance in the continuous task violated it; and (c) performance in the discrete task was influenced by continuous properties (e.g., dot density, dot cumulative area) of the dot array that were not predictive of numerosities or task relevant. Therefore, we propose that the magnitude processing system (MPS) is actually divided into separate (yet interactive) systems for discrete and continuous magnitude processing. Further subdivisions are discussed. We argue that cooperation between these systems results in a holistic comparison of magnitudes, one that takes into account continuous properties in addition to numerosities. Considering the MPS as two systems opens the door to new and important questions that shed light on both normal and impaired development of the numerical system.     

Motion and edge sensitivity in perception of object unity

Although much evidence indicates that young infants perceive unitary objects by analyzing patterns of motion, infants' abilities to perceive object unity by analyzing Gestalt properties and by integrating distinct views of an object over time are in dispute. To address these controversies, four experiments investigated adults' and infants' perception of the unity of a center-occluded, moving rod with misaligned visible edges. Both alignment information and depth information affected adults' and infants' perception of object unity in similar ways, and infants perceived object unity by integrating information about object features over time. However, infants perceived a moving, misaligned, three-dimensional object as indeterminate in its connectedness, whereas adults perceived it as connected behind the occluder. These findings indicate that the effectiveness of common motion in specifying unified surfaces across an occluder is reduced by misalignment of edges. Alignment information enhances perception of object unity either by serving directly as information for unity or by optimizing the detectability of motion-carried information for unity. In addition, young infants are able to retain information about edge orientation over short intervals in determining connectedness via a process of spatiotemporal integration.     

The assessment of protective behavioral strategies: Comparing prediction and factor structures across measures

Protective behavioral strategies (PBS), or drinking control strategies, are specific behaviors one can utilize to minimize the harmful consequences of alcohol consumption. As there is not currently a standard measure of PBS, the goal of the present study was to examine the factor structure and concurrent validity of three scales designed to assess PBS: Protective Behavioral Strategies Scale (PBSS; Martens, M. P., Ferrier, A. G., Sheehy, M. J., Corbett, K., Anderson, D. A., & Simmons, A., 2005 Development of the Protective Behavioral Strategies Survey. Journal of Studies on Alcohol, 66, 698-705), Protective Behavioral Strategies Measure (Novik, M. G., & Boekeloo, B. O., 2011, Dimensionality and psychometric analysis of an alcohol protective behavioral strategies scale. Journal of Drug Education, 41, 65-78. doi:10.2190/DE.41.1.d), and the Strategy Questionnaire (SQ); (Sugarman, D. E., & Carey, K. B., 2007), The relationship between drinking control strategies and college student alcohol use. Psychology of Addictive Behaviors, 21, 338-345. doi:10.1037/0893-164X.21.3.338). In a sample of college students (n = 291), we used confirmatory factor analysis to examine the proposed factor structures of each scale. Although the theorized three-factor structure fit the data moderately well for the PBSS, the theorized factor structures for the Protective Behavioral Strategies Measure and SQ did not fit the data well. Further, the composite scores from the PBSS were all significantly negatively correlated with alcohol-related problems, whereas the composites of the SQ were not significantly correlated with alcohol-related problems. Although we have evidence in favor of 1 PBS measure over others, we discuss broader issues related to assessment of PBS. We consider the different instructions, response scales, and time intervals for various PBS measures in terms of how they relate to the advancement of PBS research. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Perception of Genuine and Masking Smiles in Children and Adults: Sensitivity to Traces of Anger

The authors examined children's and adults' sensitivity to traces of anger in masking smiles by presenting participants with short video excerpts of smiles that differed by the intensity of an anger component. Fifty-two children, aged 6 to 12 years, and 26 adults were asked to judge whether a stimulus person was really happy or pretending to be happy. Six- and 7-year-old children were found to be sensitive to traces of anger, but less so than older children and adults. Researchers found evidence of explicit knowledge of the emotion hidden in masking smiles only in adult participants.     

Location- and object-based inhibition of return are affected by different kinds of working memory

Castel, Pratt, and Craik (2003) have shown that inhibition of return (IOR, the delayed response to a recently cued item) is disrupted by a secondary task that involves spatial working memory (WM), and they suggest that IOR is mediated by spatial WM. However, they did not specify what kind of IOR was involved. We used a dual-task paradigm to examine whether the two kinds of IOR (location- and object-based IOR) are affected by two kinds of secondary task that involve spatial and nonspatial WM, respectively. The results show that location-based IOR was disrupted by a spatial secondary task while the object-based IOR was disrupted by a nonspatial secondary task. The present study further elaborates the conclusion of Castel et al. (2003) by differentiating the effect of the two kinds of WM (spatial vs. nonspatial) on the two kinds of IOR (location based vs. object based).     

Temporal processing within and across senses

This special issue on temporal processing within and across senses was the outcome of a two-day workshop that took place in Tübingen, Germany. The aim of the workshop and this special issue was to advance our knowledge on timing and the senses and to bring together two lines of research that have not yet interacted, those of synchrony and duration perception.     

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.     

Scared stiff: The influence of anxiety on the perception of action capabilities

Influences on the perception of affordances (i.e., opportunities for actions) have been primarily studied by manipulating the functional morphology of the body. However, affordances are not just determined by the functional morphology of the perceiver, but also by the physiological state of the perceiver. States of anxiety have been shown to lead to marked changes in individuals’ physiological state and their behaviour. To assess the influence of emotional state on affordance perception, the perception of action capabilities in near space was examined after participants completed an anxiety-provoking task. Anxiety was induced immediately prior to tasks that assessed participants' perceived reaching ability in Experiment 1, grasping ability in Experiment 2, and the ability to pass their hands through apertures in Experiment 3. Results indicated that those participants who experienced changes in anxiety underestimated their reaching, grasping, and passing ability compared to non-anxious participants. In other words, anxious participants were more conservative in their estimations of their action capabilities. These results suggest that anxiety influences the perception for affordances in near space and are consistent with the notion that anxiety induces withdrawal behaviours.     

Comparing perception of signals in different modalities during the cycling task: A field study

Cyclists are considered to be amongst the most vulnerable road users and the number of cyclists involved in crashes is increasing. One possibility to improve bicycle safety is the implementation of assistance systems, for instance by providing the information needed to avoid critical situations. However, it is not known how and what kind of signals can reliably be transmitted to cyclists, in particular as warnings. This study has the objective to investigate which signal type dependent of the modality and the route type can be perceived during the cycling task. Therefore, we conducted a semi-naturalistic cycling study with 56 participants where a 10 km long, pre-defined route was individually cycled while 36 signals (visual, auditory and vibro-tactile) were transmitted. The participants signalled the perception of a signal by pressing a button. Response rates differed significantly between signal modalities. While auditory signals performed best closely followed by vibro-tactile signals, visual signals were frequently missed. The route type had an effect on the perception of the signals. The influence of the route segments with haptic interference was not expected to be this large on the perception of vibro-tactile signals. The obtained results indicate how and in which situations the different modalities are suited to transmit information to cyclists.     

The world in black and white: Ostracism enhances the categorical perception of social information

In two experiments, ostracized individuals showed more pronounced categorical perception of inclusion- and exclusion-related stimuli. Specifically, ostracism enhanced the ability to distinguish between-category differences (e.g., between happy and angry faces) relative to within-category differences (e.g., between two happy expressions). Participants were socially included or excluded via Cyberball (a virtual ball-tossing task). In Experiment 1, ostracized participants showed greater perceptual acuity in distinguishing between subtly happy and angry expressions combined with a reduced ability to discriminate expressions within each expression category. Experiment 2 found analogous categorical perception effects for targets varying on the dimension of race. Importantly, this effect was specific to social information; categorical perception of non-social objects was not qualified by social exclusion. These results suggest that ostracism exacerbates categorical perception, attuning perceivers to the differences between various inclusion- and exclusion-related categories relative to within category acuity, making the world appear more ‘black-and-white’ than it might otherwise.