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2007, volume 3, issue 1-2
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Contents:
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Ulrich Ansorge, Gregory Francis, Michael Herzog, and Haluk ÖğmenVisual masking and the dynamics of human perception, cognition, and consciousness. A century of progress, a contemporary synthesis, and future directions.
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volume 3 issue 1-2, pages 1-8 |
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Visual masking and the dynamics of human perception, cognition, and consciousness. A century of progress, a contemporary synthesis, and future directions.
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Ulrich Ansorge, Gregory Francis, Michael Herzog, and Haluk Öğmen |
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1 Abteilung für Psychologie und Sportwissenschaft, Universität Bielefeld, Germany
2 Department of Psychological Sciences, Purdue University, USA
3 Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
4 Center for Neuro-Engineering and Cognitive Science, Department of Electrical and Computer Engineering, Houston, USA
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The 1990s, the "decade of the brain", witnessed major advances in the study of visual perception, cognition, and consciousness. Impressive techniques in neurophysiology, neuroanatomy, neuropsychology, electrophysiology, psychophysics and brain-imaging were developed to address how the nervous system transforms and represents visual inputs. Many of these advances have dealt with the steady-state properties of processing. To complement this "steady-state approach", more recent research emphasized the importance of dynamic aspects of visual processing. Visual masking has been a paradigm of choice for more than a century when it comes to the study of dynamic vision. A recent workshop, held in Delmenhorst, Germany, brought together an international group of researchers to present state-of-the-art research on dynamic visual processing with a focus on visual masking. This special issue presents peer-reviewed contributions by the workshop participants and provides a contemporary synthesis of how visual masking can inform the dynamics of human perception, cognition, and consciousness.
Keywords: vision, motor control, masking, subliminal priming, consciousness, attention
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volume 3 issue 1-2, pages 9-20 |
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Visual masking: past accomplishments, present status, future developments |
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Department of Psychology, University of Houston
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Visual masking, throughout its history, has been used as an investigative tool in exploring the temporal dynamics of visual perception, beginning with retinal processes and ending in cortical processes concerned with the conscious registration of stimuli. However, visual masking also has been a phenomenon deemed worthy of study in its own right. Most of the recent uses of visual masking have focused on the study of central processes, particularly those involved in feature, object and scene representations, in attentional control mechanisms, and in phenomenal awareness. In recent years our understanding of the phenomenon and cortical mechanisms of visual masking also has benefited from several brain imaging techniques and from a number of sophisticated and neurophysiologically plausible neural network models. Key issues and problems are discussed with the aim of guiding future empirical and theoretical research.
Keywords: masking, neural networks, nonconscious/conscious processing, object perception
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volume 3 issue 1-2, pages 21-31 |
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What should a quantitative model of masking look like and why would we want it?
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1 Psychological Sciences, Purdue University, West Lafayette
2 Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne
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Quantitative models of backward masking appeared almost as soon as computing technology was available to simulate them; and continued interest in masking has lead to the development of new models. Despite this long history, the impact of the models on the field has been limited because they have fundamental shortcomings. This paper discusses these shortcomings and outlines what future quantitative models should look like. It also discusses several issues about modeling and how a model could be used by researchers to better explore masking and other aspects of cognition.
Keywords: backward masking, dynamic vision, modeling
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volume 3 issue 1-2, pages 33-40 |
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Common-onset masking simulated with
a distributed-code model |
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Department of Psychology, University of California, Santa Cruz, Ca. USA
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A distributed-coding model incorporating lateral inhibition in a simulated nerve network has been successful in accounting for many properties of backward masking (Bridgeman, 1971, 1978), linking modeling with neurophysiology and psychophysics. Metacontrast is a variety of backward masking that is of particular interest in uncovering properties of visual coding because target and mask do not overlap in time or space, and it is the first stimulus that is reduced in visibility, not the second. The lateral inhibitory model can also simulate common-onset masking, where a target and mask appear simultaneously but the mask disappears after a variable delay, and it can reproduce qualitatively the effects of attention on object substitution by varying the time interval over which sensory codes are analyzed.
Keywords: masking, metacontrast, lateral inhibition, mathematical model, object substitution, common-onset masking, backward masking, attention
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volume 3 issue 1-2, pages 41-55 |
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Binding binding: Departure points for a different version of the perceptual retouch theory |
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Department of Psychology and Institute of Law, University of Tartu
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In the perceptual retouch theory, masking and related microgenetic phenomena were explained as a result of interaction between specific cortical representational systems and the non-specific sub-cortical modulation system. Masking appears as deprivation of sufficient modulation of the consciousness mechanism suffered by the target-specific signals because of the temporal delay of non-specific modulation (necessary for conscious representation), which explicates the later-coming mask information instead of the already decayed target information. The core of the model envisaged relative magnitudes of EPSPs of single cortical cells driven by target and mask signals at the moment when the nonspecific, presynaptic, excitatory input arrives from the thalamus. In the light of the current evidence about the importance of synchronised activity of specific and non-specific systems in generating consciousness, the retouch theory requires perhaps a different view. This article presents some premises for modification of the retouch theory, where instead of the cumulative presynaptic spike activities and EPSPs of single cells, the oscillatory activity in the gamma range of the participating systems is considered and shown to be consistent with the basic ideas of the retouch theory. In this conceptualisation, O-binding refers to specific encoding which is based on gamma-band synchronised oscillations in the activity of specific cortical sensory modules that represent features and objects; C-binding refers to the gamma-band oscillations in the activity of the non-specific thalamic systems, which is necessary for the O-binding based data to become consciously experienced.
Keywords: masking, consciousness, perceptual retouch, thalamic modulation, synchronization, gamma-oscillations
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volume 3 issue 1-2, pages 57-65 |
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An analysis of visual masking, with a defense
of "Stopped Processing" |
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Dept. of Psychology, Northeastern University, Boston, USA
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The use of a backward mask (a patterned mask which follows the target in time) to "stop the processing" of the target illustrates an important application of masking - the study of the "microgenesis" of visual perception, that is, visual processing over about the first one-fifth of a second. This paper provides evidence for stopped processing and some applications of this to object recognition and letter detection. The paper also discusses the notion of an "active filter" which may help to account for Type-A masking but at best can only account for Type-B masking in part. I conclude that masking, while illuminating various areas of vision science, is under-utilized, perhaps because the theoretical justification for such masking is still uncertain, and perhaps because of the care needed to establish that the mask does indeed "stop" processing.
Keywords: masking, metacontrast, stopped processing
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Haluk ÖğmenA theory of moving form perception: Synergy
between masking, perceptual grouping,
and motion computation in retinotopic and
non-retinotopic representations
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volume 3 issue 1-2, pages 67-84 |
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A theory of moving form perception: Synergy
between masking, perceptual grouping,
and motion computation in retinotopic and
non-retinotopic representations
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Department of Electrical & Computer Engineering, Center for Neuro-Engineering & Cognitive Science, University of Houston, Houston, TX 77204-4005 USA
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Because object and self-motion are ubiquitous in natural viewing conditions, understanding how the human visual system achieves a relatively clear perception for moving objects is a fundamental problem in visual perception. Several studies have shown that the visible persistence of a briefly presented stationary stimulus is approximately 120 ms under normal viewing conditions. Based on this duration of visible persistence, we would expect moving objects to appear highly blurred. However, in human vision, objects in motion typically appear relatively sharp and clear. We suggest that clarity of form in dynamic viewing is achieved by a synergy between masking, perceptual grouping, and motion computation across retinotopic and non-retinotopic representations. We also argue that dissociations observed in masking are essential to create and maintain this synergy.
Keywords: moving form perception, dynamic form perception, visual masking, perceptual grouping, motion
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volume 3 issue 1-2, pages 85-92 |
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Spatial processing and visual backward
masking
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Laboratory of Psychophysics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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Most theories of visual masking focus primarily on the temporal aspects of visual information processing, strongly neglecting spatial factors. In recent years, however, we have shown that this position is not tenable. Spatial aspects cannot be neglected in metacontrast, pattern and un-masking. Here, we review these results.
Keywords: temporal processing, verniers, unmasking, metacontrast
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volume 3 issue 1-2, pages 93-105 |
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Visual backward masking: Modeling spatial
and temporal aspects
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Frouke Hermens and Udo Ernst |
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1 Laboratory of Psychophysics, Brain Mind Institutem, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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2 Group for Neural Theory, Département d'Etudes Cognitives (DEC), École Normale, Supérieure (ENS), Paris, France
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In modeling visual backward masking, the focus has been on temporal effects. More specifically, an explanation has been sought as to why strongest masking can occur when the mask is delayed with respect to the target. Although interesting effects of the spatial layout of the mask have been found, only a few attempts have been made to model these phenomena. Here, we elaborate a structurally simple model which employs lateral excitation and inhibition together with different neural time scales to explain many spatial and temporal aspects of backward masking. We argue that for better understanding of visual masking, it is vitally important to consider the interplay of spatial and temporal factors together in one single model.
Keywords: visual backward masking
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volume 3 issue 1-2, pages 107-109 |
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Grouping based feature attribution
in metacontrast masking
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Laboratory of Psychophysics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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The visibility of a target can be strongly suppressed by metacontrast masking. Still, some features of the target can be perceived within the mask. Usually, these rare cases of feature mis-localizations are assumed to reflect errors of the visual system. To the contrary, I will show that feature "mis-localizations" in metacontrast masking follow rules of motion grouping and, hence, should be viewed as part of a systematic feature attribution process.
Keywords: metacontrast masking, feature attribution, feature integration, motion grouping, attention
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volume 3 issue 1-2, pages 111-123 |
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The mechanisms of feature inheritance as
predicted by a systems-level model of visual
attention and decision making
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Department of Psychology, Westf.-Wilhelms-Universität Münster, Germany
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Feature inheritance provides evidence that properties of an invisible target stimulus can be attached to a following mask. We apply a systems level model of attention and decision making to explore the influence of memory and feedback connections in feature inheritance. We find that the presence of feedback loops alone is sufficient to account for feature inheritance. Although our simulations do not cover all experimental variations and focus only on the general principle, our result appears of specific interest since the model was designed for a completely different purpose than to explain feature inheritance. We suggest that feedback is an important property in visual perception and provide a description of its mechanism and its role in perception.
Keywords: feature inheritance, attention, decision making, feedback, VSTM, computational model
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volume 3 issue 1-2, pages 125-152 |
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The role of feedback in visual masking and
visual processing
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Stephen L. Macknik and Susana Martinez-Conde |
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Barrow Neurological Institute, Phoenix, USA
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This paper reviews the potential role of feedback in visual masking, for and against. Our analysis reveals constraints for feedback mechanisms that limit their potential role in visual masking, and in all other general brain functions. We propose a feedforward model of visual masking, and provide a hypothesis to explain the role of feedback in visual masking and visual processing in general. We review the anatomy and physiology of feedback mechanisms, and propose that the massive ratio of feedback versus feedforward connections in the visual system may be explained solely by the critical need for top-down attentional modulation. We discuss the merits of visual masking as a tool to discover the neural correlates of consciousness, especially as compared to other popular illusions, such as binocular rivalry. Finally, we propose a new set of neurophysiological standards needed to establish whether any given neuron or brain circuit may be the neural substrate of awareness.
Keywords: visual, masking, feedback, humans, monkeys, metacontrast, paracontrast, electrophysiology, optical imaging, fMRI, psychophysics, vision, awareness, attention, consciousness, standing wave
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volume 3 issue 1-2, pages 153-165 |
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Spatio-temporal low-level neural networks
account for visual masking
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Uri Polat, Anna Sterkin, and Oren Yehezkel |
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Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel
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Temporal masking is a paradigm that is widely used to study visual information processing. When a mask is presented, typically within less than 100 msec before or after the target, the response to the target is reduced. The results of our psychophysical and visual evoked potential (VEP) experiments show that the masking effect critically depends on a combination of several factors: (1) the processing time of the target, (2) the order of presentation of the target and the mask, and (3) the spatial arrangement of the target and the mask. Thus, the masking effect depends on the spatial-temporal combination of these factors. Suppression was observed when the mask was positioned within a spatial range that was found to evoke inhibition, and when the temporal separation between the target and the mask was short. In contrast, lateral facilitation was observed when the mask was presented at a spatial separation that did not evoke inhibition from the target?s vicinity and with a temporal sequence that preceded the target, or when it was presented simultaneously with it, but not when the target preceded the mask. We propose that masking effects, either suppression or facilitation, reflect integration into the spatial and the temporal domains of the feedforward response to the target and the lateral inputs evoked by the mask (excitatory and/or inhibitory). Because the excitation evoked by the mask develops and propagates slowly from the mask?s location to the target?s location, it lags behind the response to the target. On the other hand, inhibition that is produced in the vicinity of the target evolves more rapidly and follows the onset and offset of the stimulus more closely. Thus, lateral excitation that overcomes the inhibition may facilitate the grouping of local elements into a global percept by increasing the survivability of the object and its accessibility for perceptual awareness.
Keywords: temporal processing, visual masking, spatio-temporal interactions, temporal masking, visual evoked potentials, psychophysics
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volume 3 issue 1-2, pages 167-176 |
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The power of the feed-forward sweep |
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Centre de Recherche Cerveau et Cognition, CNRS, Université Toulouse 3, 31062 Toulouse Cedex 9, France.
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Vision is fast and efficient. A novel natural scene can be categorized (e.g. does it contain an animal, a vehicle?) by human observers in less than 150 ms, and with minimal attentional resources. This ability still holds under strong backward masking conditions. In fact, with a stimulus onset asynchrony of about 30 ms (the time between the scene and mask onset), the first 30 ms of selective behavioral responses are essentially unaffected by the presence of the mask, suggesting that this type of ?ultra-rapid? processing can rely on a sequence of swift feedforward stages, in which the mask information never ?catches up? with the scene information. Simulations show that the feed-forward propagation of the first wave of spikes generated at stimulus onset may indeed suffice for crude recognition or categorization. Scene awareness, however, may take significantly more time to develop, and probably requires feed-back processes. The main implication of these results for theories of masking is that pattern or metacontrast (backward) masking do not appear to bar the progression of visual information at a low level. These ideas bear interesting similarities to existing conceptualizations of priming and masking, such as Direct Parameter Specification or the Rapid Chase theory.
Keywords: natural scenes, ultra-rapid categorization, pre-attentive recognition, backward masking, feed-forward, processing, spike timing
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volume 3 issue 1-2, pages 177-179 |
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Visual masking by transcranial magnetic
stimulation in the first 80 milliseconds
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Department of Psychiatry, University of Ulm, Germany
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Stimulation of the occipital cortex with transcranial magnetic stimulation (TMS) can interfere with visual processing and may cause masking comparable to visual masking. The effect is most pronounced when the TMS pulse is delivered with stimulus onset asynchronies (SOAs) of 80-100 ms. In a few experiments a second time window of TMS-induced visual masking has been identified with its maximum around an SOA of 40 ms. The existence of two masking windows has been taken as evidence for two distinct visual processes taking place in V1: an early feedforward component and a later re-entrant feedback component. The evidence for the existence of two separate TMS time windows is reviewed. The early time window was not reproducible in all the attempts to characterize TMS masking effects. Interindividual anatomical differences in the location of V1 might contribute to the heterogeneous results.
Keywords: visual cortex, masking, feedforward, re-entrant, magnetic stimulation
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volume 3 issue 1-2, pages 181-192 |
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What determines the direction of subliminal
priming
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Piotr Jaśkowski and Rolf Verleger |
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1 Department of Cognitive Psychology, University of Finance and Management, Warszawa, Poland
2 Department of Neurology, University of Luebeck, Germany
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Masked stimuli (primes) can affect the preparation of a motor response to subsequently presented target stimuli. Reactions to the target can be facilitated (straight priming) or inhibited (inverse priming) when preceded by a compatible prime (calling for the same response) and also when preceded by an incompatible prime. Several hypotheses are currently under debate. These are the self-inhibition (SI) hypothesis, the object-updating (OU) hypothesis, and masktriggered inhibition (MTI) hypothesis. All assume that the initial activation of the motor response is elicited by the prime according to its identity. This activation inevitably leads to straight priming in some cases and the mechanisms involved are undisputed. The hypotheses differ, however, as to why inverse priming occurs. The self-inhibition (SI) hypothesis assumes that the motor activation elicited by a prime is automatically followed by an inhibition phase, leading to inverse priming if three conditions are fulfilled: perceptual evidence for the prime has to be sufficiently strong, it has to be immediately removed by the mask, and the delay between the prime and target has to be long enough for inhibition to become effective. The object-updating (OU) hypothesis assumes that inverse priming is triggered by the mask, provided that it contains features calling for the alternative response (i.e. the one contrasting with the response induced by the prime). The MTI hypothesis assumes that the inhibitory phase is triggered by each successive stimulus which does not support the perceptual hypothesis provided by the prime. Based mostly on our own experiments, we argue that (1) attempts to manipulate the three factors required by the SI hypothesis imply changes of other variables and that (2) indeed, other variables seem to affect priming: prime-mask perceptual interaction and temporal position of the mask. These observations are in favor of the MTI hypothesis. A limiting factor for all three hypotheses is that inverse priming is larger for arrows than for other shapes, making it doubtful as to what extent the majority of studies on inverse priming, due to their use of arrows, can be generalized to other stimuli.
Keywords: subliminal priming, inverse and straight priming, backward masking
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Rolf Verleger and Piotr JaśkowskiDisentangling neural processing of masked
and masking stimulus by means of
event-related contralateral-ipsilateral
differences of EEG potentials
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volume 3 issue 1-2, pages 193-210 |
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Disentangling neural processing of masked
and masking stimulus by means of
event-related contralateral-ipsilateral
differences of EEG potentials
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Rolf Verleger and Piotr Jaśkowski |
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1 Department of Neurology, University of Lübeck, Germany
2 Department of Cognitive Neuroscience, University of Finance and Management, Warszawa, Poland
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In spite of the excellent temporal resolution of event-related EEG potentials (ERPs), the overlapping potentials evoked by masked and masking stimuli are hard to disentangle. However, when both masked and masking stimuli consist of pairs of relevant and irrelevant stimuli, one left and one right from fixation, with the side of the relevant element varying between pairs, effects of masked and masking stimuli can be distinguished by means of the contralateral preponderance of the potentials evoked by the relevant elements, because the relevant elements may independently change sides in masked and masking stimuli. Based on a reanalysis of data from which only selected contralateral-ipsilateral effects had been previously published, the present contribution will provide a more complete picture of the ERP effects in a masked-priming task. Indeed, effects evoked by masked primes and masking targets heavily overlapped in conventional ERPs and could be disentangled to a certain degree by contralateral-ipsilateral differences. Their major component, the N2pc, is interpreted as indicating preferential processing of stimuli matching the target template, which process can neither be identified with conscious perception nor with shifts of spatial attention. The measurements showed that the triggering of response preparation by the masked stimuli did not depend on their discriminability, and their priming effects on the processing of the following target stimuli were qualitatively different for stimulus identification and for response preparation. These results provide another piece of evidence for the independence of motor-related and perception-related effects of masked stimuli.
Keywords: event-related potentials, masking, masked priming, N2pc, LRP, N2cc
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volume 3 issue 1-2, pages 211-226 |
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Visual similarity in masking and priming:
The critical role of task relevance
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James T. Enns and Chris Oriet |
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1 University of British Columbia
2 University of Regina
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Cognitive scientists use rapid image sequences to study both the emergence of conscious perception (visual masking) and the unconscious processes involved in response preparation (masked priming). The present study asked two questions: (1) Does image similarity influence masking and priming in the same way? (2) Are similarity effects in both tasks governed by the extent of feature overlap in the images or only by task-relevant features? Participants in Experiment 1 classified human faces using a single dimension even though the faces varied in three dimensions (emotion, race, sex). Abstract geometric shapes and colors were tested in the same way in Experiment 2. Results showed that similarity reduced the visibility of the target in the masking task and increased response speed in the priming task, pointing to a double-dissociation between the two tasks. Results also showed that only task-relevant (not objective) similarity influenced masking and priming, implying that both tasks are influenced from the beginning by intentions of the participant. These findings are interpreted within the framework of a reentrant theory of visual perception. They imply that intentions can influence object formation prior to the separation of vision for perception and vision for action.
Keywords: masking, priming, task-relevance, visual similarity, reentrant processing
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Friederike Schlaghecken, Laura Rowley, Sukhdev Sembi, Rachel Simmons, and Daniel WhitcombThe negative compatibility effect: A case for self-inhibition
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volume 3 issue 1-2, pages 227-240 |
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The negative compatibility effect: A case for self-inhibition
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Friederike Schlaghecken, Laura Rowley, Sukhdev Sembi, Rachel Simmons, and Daniel Whitcomb |
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Department of Psychology, University of Warwick, Coventry, UK
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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 (NCEs) 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).
Keywords: masked priming, negative compatibility effect, inhibition
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volume 3 issue 1-2, pages 241-255 |
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Temporal processes in prime-mask interaction:
Assessing perceptual consequences of masked
information
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Department of Psychology, Bielefeld University, Germany
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Visual backward masking is frequently used to study the temporal dynamics of visual perception. These dynamics may include the temporal features of conscious percepts, as suggested, for instance, by the asynchronous-updating model (Neumann, 1982) and perceptual-retouch theory (Bachmann, 1994). These models predict that the perceptual latency of a visual backward mask is shorter than that of a like reference stimulus that was not preceded by a masked stimulus. The prediction has been confirmed by studies using temporal-order judgments: For certain asynchronies between mask and reference stimulus, temporal-order reversals are quite frequent (e.g. Scharlau, & Neumann, 2003a). However, it may be argued that these reversals were due to a response bias in favour of the mask rather than true temporal perceptual effects. I introduce two measures for assessing latency effects that (1) are not prone to such a response bias, (2) allow to quantify the latency gain, and (3) extend the perceptual evidence from order reversals to duration/interval perception, that is, demonstrate that the perceived interval between a mask and a reference stimulus may be shortened as well as prolonged by the presence of a masked stimulus. Consequences for theories of visual masking such as asynchronous-updating, perceptual-retouch, and reentrant models are discussed.
Keywords: masked priming, attention, visual backward masking, metacontrast, perceptual latency, perception of time
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Ulrich Ansorge, Odmar Neumann, Stefanie I. Becker, Holger Kälberer, and Holk CruseSensorimotor supremacy: Investigating
conscious and unconscious vision by masked
priming
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volume 3 issue 1-2, pages 257-274 |
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Sensorimotor supremacy: Investigating
conscious and unconscious vision by masked
priming |
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Ulrich Ansorge, Odmar Neumann, Stefanie I. Becker, Holger Kälberer, and Holk Cruse |
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Department of Psychology, Universität Bielefeld, Bielefeld, Germany
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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.
Keywords: masked priming, vision, sensorimotor processing, attention
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volume 3 issue 1-2, pages 275-287 |
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Measuring unconscious cognition: Beyond the
zero-awareness criterion
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Department of Cognitive Psychology, University of Giessen, Germany
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Visual masking can be employed to manipulate observers? awareness of critical stimuli in studies of masked priming. This paper discusses two different lines of attack for establishing unconscious cognition in such experiments. Firstly, simple dissociations between direct measures (D) of visual awareness and indirect measures (I) of processing per se occur when I has some nonzero value while D is at chance level; the traditional requirement of zero awareness is necessary for this criterion only. In contrast, double dissociations occur when some experimental manipulation has opposite effects on I and D, for instance, increasing priming effects despite decreasing prime identification performance (Schmidt & Vorberg, 2006). Double dissociations require much weaker measurement assumptions than other criteria. An attractive alternative to this dissociation approach would be to use tasks that are known to violate necessary conditions of visual awareness altogether. In particular, it is argued here that priming effects in speeded pointing movements (Schmidt, Niehaus, & Nagel, 2006) occur in the absence of the recurrent processing that is often assumed to be a necessary condition for awareness (for instance, DiLollo, Enns, & Rensink, 2000; Lamme & Roelfsema, 2000). Feedforward tasks such as this might thus be used to measure the time-course of unconscious processing directly, before intracortical feedback and awareness come into play.
Keywords: response, priming, masking, visual awareness, dissociations, feedforward sweep
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volume 3 issue 1-2, pages 289-306 |
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Top-down modulation of unconscious
"automatic" processes: A gating framework
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University of Ulm, Department of Psychiatry, Germany
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In classical theories of automaticity, automatic processes are usually thought to occur autonomously and independently of higher level topdown factors (e.g., Posner & Snyder, 1975). However, already Neumann (1984) pointed out that the cognitive system has to be configured in a certain way for automatic processes to occur. In extension of his work, I propose a gating framework to account for the influence of top-down factors such as attention, intention and task set on automatic processes such as masked response or semantic priming. It is assumed that task representations held in prefrontal cortex regulate the gain of neurons in visual and sematic association cortex thereby modulating the effects of unconsciously perceived masked stimuli on further "automatic" information processing steps. In support of the postulated gating framework, recent studies demonstrated a top-down modulation of automatic processes. Behavioral and electrophysiological studies with the masked response priming and semantic priming paradigms show that masked priming effects crucially depend (i) on temporal attention to the masked prime, (ii) on intentions or action plans and (iii) on the task set active immediately before masked prime presentation. For instance, masked semantic priming was only observed when the preceding task set required the orientation to semantic word features, but not when it required orientation to perceptual word features. These results support the view that unconscious automatic processes are modulated by top-down factors. They are suggestive of a gating mechanism which orchestrates the conscious and unconscious information processing streams.
Keywords: automatic processes, unconscious perception, masked semantic, priming, masked response priming, top-down control
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volume 3 issue 1-2, pages 307-315 |
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Mechanisms of subliminal response priming |
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Andrea Kiesel, Wilfried Kunde, and Joachim Hoffmann |
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1 Department of Psychology, Julius-Maximilians University of Würzburg, Germany
2 Department of Psychology, Martin-Luther-University Halle-Wittenberg, Germany
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Subliminal response priming has been considered to operate on several stages, e.g. perceptual, central or motor stages might be affected. While primes? impact on target perception has been clearly demonstrated, semantic response priming recently has been thrown into doubt (e.g. Klinger, Burton, & Pitts, 2000). Finally, LRP studies have revealed that subliminal primes evoke motor processes. Yet, the premises for such prime-evoked motor activation are not settled. A transfer of priming to stimuli that have never been presented as targets appears particularly interesting because it suggests a level of processing that goes beyond a reactivation of previously acquired S-R links. Yet, such transfer has not always withstood empirical testing. To account for these contradictory results, we proposed a two-process model (Kunde, Kiesel, & Hoffmann, 2003): First, participants build up expectations regarding imperative stimuli for the required responses according to experience and/or instructions. Second, stimuli that match these "action triggers" directly activate the corresponding motor responses irrespective of their conscious identification. In line with these assumptions, recent studies revealed that non-target primes induce priming when they fit the current task intentions and when they are expected in the experimental setting.
Keywords: subliminal priming, priming mechanism, action trigger account
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volume 3 issue 1-2, pages 317-326 |
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Negative and positive masked-priming
- implications for motor inhibition
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Cardiff University, Cardiff, UK
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Masked stimuli can prime responses to subsequent target stimuli, causing response benefits when the prime is similar to the target. However, one masked-prime paradigm has produced counter-intuitive negative compatibility effects (NCE), such that performance costs occur when prime and target are similar. This NCE has been interpreted as an index of an automatic self-inhibition mechanism that suppresses the partial motor activation caused by the prime. However, several alternative explanations for the NCE have been proposed and supported by new evidence. As a framework for discussion, I divide the original theory into five potentially separable issues and briefly examine each with regard to alternative theories and current evidence. These issues are: 1) whether the NCE is caused by motor inhibition or perceptual interactions; 2) whether inhibition is self-triggered or stimulus-triggered; 3) whether prime visibility plays a causal role; 4) whether there is a threshold for triggering inhibition; 5) whether inhibition is automatic. Lastly, I briefly consider why NCEs have not been reported in other priming paradigms, and what the neural substrate for any automatic motor inhibition might be.
Keywords: object updating, active mask, automatic, subliminal
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26
Michael E. RuddMetacontrast masking and the cortical
representation of surface color: dynamical
aspects of edge integration and contrast gain
control
[download pdf]
, [abstract (show/hide)]
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volume 3 issue 1-2, pages 327-347 |
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Metacontrast masking and the cortical
representation of surface color: dynamical
aspects of edge integration and contrast gain
control
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Howard Hughes Medical Institute and Department of Physiology and Biophysics
University of Washington, Seattle, WA USA
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This paper reviews recent theoretical and experimental work supporting the idea that brightness is computed in a series of neural stages involving edge integration and contrast gain control. It is proposed here that metacontrast and paracontrast masking occur as byproducts of the dynamical properties of these neural mechanisms. The brightness computation model assumes, more specifically, that early visual neurons in the retina, and cortical areas V1 and V2, encode local edge signals whose magnitudes are proportional to the logarithms of the luminance ratios at luminance edges within the retinal image. These local edge signals give rise to secondary neural lightness and darkness spatial induction signals, which are summed at a later stage of cortical processing to produce a neural representation of surface color, or achromatic color, in the case of the chromatically neutral stimuli considered here. Prior to the spatial summation of these edge-based induction signals, the weights assigned to local edge contrast are adjusted by cortical gain mechanisms involving both lateral interactions between neural edge detectors and top-down attentional control. We have previously constructed and computer-simulated a neural model of achromatic color perception based on these principles and have shown that our model gives a good quantitative account of the results of several brightness matching experiments. Adding to this model the realistic dynamical assumptions that 1) the neurons that encode local contrast exhibit transient firing rate enhancement at the onset of an edge, and 2) that the effects of contrast gain control take time to spread between edges, results in a dynamic model of brightness computation that predicts the existence Broca-Sulzer transient brightness enhancement of the target, Type B metacontrast masking, and a form of paracontrast masking in which the target brightness is enhanced when the mask precedes the target in time.
Keywords: edge integration, brightness, lightness, achromatic color, brightness induction, masking, metacontrast, paracontrast, type B masking
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volume 3 issue 1-2, pages 349-359 |
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Concepts of visual consciousness and their measurement
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1 Department of Psychology, Stockholm University, Stockholm, Sweden
2 Psychology Section, Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
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Although visual consciousness can be manipulated easily (e.g., by visual masking), it is unresolved whether it can be assessed accurately with behavioral measures such as discrimination ability and self-report. Older theories of visual consciousness postulated a sensory threshold and distinguished between subjective and objective thresholds. In contrast, newer theories distinguish among three aspects: phenomenal, access, and reflexiveconsciousness.Thisreviewshows that discrimination ability and self-report differ in their sensitivity to these aspects. Therefore, both need to be assessed in the study of visual consciousness.
Keywords: consciousness, awareness, phenomenology, objective, subjective, blindsight
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volume 3 issue 1-2, pages 361 |
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Metzger's Challenge. "Laws of seeing" by Wolfgang Metzger BOOK REVIEW
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Dept. of Psychology, Northeastern University,
Boston MA, USA
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Contents:
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1
Markus Kiefer, Stefanie Schuch, Wolfram Schenck, and Klaus FiedlerEmotion and memory: Event-related potential indices predictive for subsequent successful memory depend on the emotional mood state
[download pdf]
, [abstract (show/hide)]
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volume 3 issue 3, pages 363-373 |
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Emotion and memory: Event-related potential indices predictive for subsequent successful memory depend on the emotional mood state |
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Markus Kiefer, Stefanie Schuch, Wolfram Schenck, and Klaus Fiedler |
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1 University of Ulm, Department of Psychiatry, Ulm, Germany
2 University of Wales, Department of Psychology, Bangor, UK
3 University of Bielefeld, Department of Technology, Bielefeld, Germany
4 University of Heidelberg, Department of Psychology, Heidelberg, Germany
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The present research investigated the influencesof emotional mood states on cognitive processes and neural circuits during long-term memory encoding using event-related potentials (ERPs). We assessed whether the subsequent memory effect (SME), an electrophysiological index of successful memory encoding, varies as a function
of participants' current mood state. ERPs were recorded while participants in good or bad mood states were presented with words that had to be memorized for subsequent recall. In contrast
to participants in bad mood, participants in good mood most frequently applied elaborative encoding styles. At the neurophysiological level, ERP analyses showed that potentials to subsequently
recalled words were more positive than to forgotten words at central electrodes in the time interval of 500-650 ms after stimulus onset (SME). At fronto-central electrodes, a polarity-reversed SME was obtained. The strongest modulations
of the SME by participants' mood state were obtained at fronto-temporal electrodes. These differences in the scalp topography of the SME suggest that successful recall relies on partially
separable neural circuits for good and bad mood states. The results are consistent with theoretical
accounts of the interface between emotion
and cognition that propose mood-dependent
cognitive styles.
Keywords: episodic memory, emotion, cognitive styles, subsequent memory effect, event-related potentials
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volume 3 issue 3, pages 375-387 |
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Orientation tuning of a two-stimulus afterimage:
Implications for theories of filling-in |
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Daniel R. Van Horn and Gregory Francis |
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1Psychological Sciences, Purdue University,West Lafayette, IN, USA
2Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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Sequential viewing of 2 orthogonally related gratings produces an afterimage related to the first grating (Vidyasagar, Buzas, Kisyarday, & Eysel, 1999; Francis & Rothmayer, 2003). We investigated how the appearance of the afterimage depended on the relative orientations of the 2 stimulus gratings. We first analyze the theoretical
explanation of the appearance of the afterimage
that was proposed by Francis and Rothameyer
(2003). From the analysis, we show that the model must predict a rapid drop in afterimage
occurrence as the gratings deviate from orthogonal.
We also show that the model predicts that the shape of the afterimage should always be orthogonal to the second grating. We then report
on 2 experiments that test the properties of the model and find that the experimental data are strikingly different from the model predictions.
From these discrepancies we identify the key deficits of the current version of the model.
Keywords: afterimage, brightness perception, filling-in
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volume 3 issue 3, pages 389-397 |
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The process of spatial knowledge
acquisition in a square and a circular virtual environment |
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Petra Jansen-Osmann and Martin Heil |
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Department of Experimental Psychology, Heinrich-Heine-Universität Düsseldorf, Germany
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This study investigated the effect of the environmental
structure (circular vs. square environment)
on spatial knowledge acquisition in a desktop
virtual situation in which self-determined movement was allowed with a total of 120 participants:
7-, 8-year-old children; 11, 12-year-old children, and adults. In all measurements of spatial knowledge acquisition an overall developmental
performance increase from younger children to adults was found. In contrast to that, the exploration and learning behavior did not differ between adults and children. Furthermore, the environmental structure influenced the number
of trials needed to learn the two routes used and the distance walked to the determined landmarks.
All these tasks were easier in a circular than in a square environment. This influence of the environmental structure was absent in the direction estimations task. The advantage of spatial knowledge acquisition in a circular environment
in three of four tasks is discussed.
Keywords: spatial cognition, spatial knowledge, children, development, virtual environments
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volume 3 issue 3, pages 399-407 |
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Further evidence that not all executive functions are equal |
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Department of Educational Foundations and Special Services, Kent State University, Kent, Ohio, USA
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The current study presents a comparison of 2 structural equation models describing the relationship between the executive functions of updating and inhibiting. Although it has been argued that working memory capacity is defined by one?s ability to control the focus of attention, the findings of the current study support a view of the executive control of attention that reflects updating and inhibiting as not entirely dependent on the same resources.
Keywords: working memory, executive functions
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5
John F. Stins, Tinca J. C. Polderman, Dorret I. Boomsma, and Eco J. C. de GeusConditional accuracy in response interference tasks: Evidence from the Eriksen flanker task and the spatial conflict task
[download pdf]
, [abstract (show/hide)]
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volume 3 issue 3, pages 409-417 |
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Conditional accuracy in response interference tasks: Evidence from the Eriksen flanker task and the spatial conflict task |
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John F. Stins, Tinca J. C. Polderman, Dorret I. Boomsma, and Eco J. C. de Geus |
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1 Department of Biological Psychology, Vrije Universiteit, Amsterdam, the Netherlands
2 Research Institute MOVE, Faculty of Human Movement Sciences, VU University, Amsterdam, the Netherlands
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Two well-known response interference tasks are the Eriksen flanker task and the spatial conflict task. The tasks are logically equivalent, and comparable
effects of current and previous stimulus
type (congruent or incongruent) have been shown with regard to reaction time (RT). Here, we investigated whether interference and sequential
trial effects also had comparable effects on accuracy. We specifically tested whether these effects interacted with the speed of responding using conditional accuracy functions (CAFs). The CAFs revealed that in both tasks congruency and sequential trial effects on accuracy are found only in trials with fast responses (< 600 ms). Sequential
trial effects on accuracy were weaker for the flanker task than for the spatial conflict task. In very fast trials (< 400 ms) response activation by distracting flankers led to below-chance performance
in the flanker task, but response activation by incongruent spatial location did not lead to below-chance performance in the spatial conflict task. The pattern of results hints at subtle differences
in processing architecture between the tasks.
Keywords: response interference, sequential analysis, accuracy, Simon task, flanker
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Contents:
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volume 3 issue 4, pages 419-428 |
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The role of spatial and temporal information in biological motion perception |
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Joachim Lange and Markus Lappe |
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1 Department of Psychology II, University of Muenster, Germany
2 F.C. Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands
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Point-light biological motion stimuli provide spatio-temporal information about the structure of the human body in motion. Manipulation of the spatial structure of point-light stimuli reduces
the ability of human observers to perceive biological motion. A recent study has reported that interference with the spatial structure of point light walkers also reduces the evoked event related potentials over the occipitotemporal cortex, but that interference with the temporal structure of the stimuli evoked event-related potentials similar to normal biological motion stimuli. We systematically investigated the influence of spatial and temporal manipulation on 2 common
discrimination tasks and compared it with predictions of a neurocomputational model previously proposed. This model first analyzes the spatial structure of the stimulus independently of the temporal information to derive body posture and subsequently analyzes the temporal sequence of body postures to derive movement direction. Similar to the model predictions, the psychophysical results show that human observers need only intact spatial configuration of the stimulus to discriminate the facing direction of a point-light walker. In contrast, movement direction discrimination needs a fully intact spatio-temporal pattern of the stimulus. The activation levels in the model predict the observed event related potentials for the spatial and temporal manipulations.
Keywords: biological motion, model, task dependency, event-related potentials
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2
Jutta S. Mayer, Robert A. Bittner, David E. J. Linden, and Danko NikolićAttentional demand influences strategies
for encoding into visual working memory
[download pdf]
, [abstract (show/hide)]
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volume 3 issue 4, pages 429-448 |
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Attentional demand influences strategies
for encoding into visual working memory |
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Jutta S. Mayer, Robert A. Bittner, David E. J. Linden, and Danko Nikolić |
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1 Laboratory for Neurophysiology and Neuroimaging, Department of Psychiatry,
Johann Wolfgang Goethe-University, Frankfurt, Germany
2 School of Psychology, University of Wales, Bangor, United Kingdom
3 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-University, Frankfurt, Germany
4 Max Planck Institute for Brain Research, Frankfurt, Germany
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Visual selective attention and visual working memory (WM) share the same capacity-limited resources. We investigated whether and how participants can cope with a task in which these 2 mechanisms interfere. The task required participants to scan an array of 9 objects in order to select the target locations and to encode the items presented at these locations into WM (1 to 5 shapes). Determination of the target locations required either few attentional resources ("popout condition") or an attention-demanding serial search ("non pop-out condition"). Participants were able to achieve high memory performance in all stimulation conditions but, in the non popout conditions, this came at the cost of additional processing time. Both empirical evidence and subjective reports suggest that participants invested the additional time in memorizing the locations of all target objects prior to the encoding of their shapes into WM. Thus, they seemed to be unable to interleave the steps of search with those of encoding. We propose that the memory for target locations substitutes for perceptual pop-out and thus may be the key component that allows for flexible coping with the common processing limitations of visual WM and attention. The findings have implications for understanding how we cope with real-life situations in which the demands on visual attention and WM occur simultaneously.
Keywords: attention, working memory, interference, encoding strategies
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3
Werner Klotz, Manfred Heumann, Ulrich Ansorge, and Odmar NeumannElectrophysiological activation by masked primes: Independence of prime-related and target-related activities
[download pdf]
, [abstract (show/hide)]
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volume 3 issue 4, pages 449-465 |
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Electrophysiological activation by masked primes: Independence of prime-related and target-related activities |
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Werner Klotz, Manfred Heumann, Ulrich Ansorge, and Odmar Neumann |
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1 Department of Psychology, University of Bielefeld, Bielefeld, Germany
2 Department of Cognitive Science and Department of Psychology, University of Osnabrueck, Osnabrueck, Germany
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Visual stimuli that are made invisible by metacontrast masking (primes) have a marked influence on behavioral and psychophysiological measures such as reaction time (RT) and the lateralized readiness potential (LRP). 4 experiments
are reported that shed light on the effects that masked primes have on the LRP. Participants had a go-nogo task in which the prime was associated with 1 of 2 responses even if the target required participants to refrain from responding. To analyze the electrophysiological responses, we computed the LRP and applied an averaging method separating the activation due to the prime and the target. The results demonstrated that (a) masked primes activate responses even in a nogo situation, (b) this prime-related activation is independent of masking, (c) and is also independent of whether prime and target require the same responses (congruent condition) or different responses (incongruent condition).
Keywords: metacontrast, EEG recording, LRP, Go/Nogo
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