Object-based attention without awareness

Attention and awareness are often considered to be related. Some forms of attention can, however, facilitate the processing of stimuli that remain unseen. It is unclear whether this dissociation extends beyond selection on the basis of primitive properties, such as spatial location, to situations in which there are more complex bases for attentional selection. The experiment described here shows that attentional selection at the level of objects can take place without giving rise to awareness of those objects. Pairs of objects were continually masked, which rendered them invisible to participants performing a cued-target-discrimination task. When the cue and target appeared within the same object, discrimination was faster than when they appeared in different objects at the same spatial separation. Participants reported no awareness of the objects and were unable to detect them in a signal-detection task. Object-based attention, therefore, is not sufficient for object awareness

Does unconscious perception really exist? Continuing the ASSC20 debate

In our ASSC20 symposium, “Does unconscious perception really exist?”, the four of us asked some difficult questions about the purported phenomenon of unconscious perception, disagreeing on a number of points. This disagreement reflected the objective of the symposium: not only to come together to discuss a single topic of keen interest to the ASSC community, but to do so in a way that would fairly and comprehensively represent the heterogeneity of ideas, opinions, and evidence that exists concerning this contentious topic. The crux of this controversy rests in no small part on disagreement about what is meant by the terms of the debate and how to determine empirically whether a state is unconscious or not. These are issues that directly concern all of us who study consciousness, so it seems it would be in our best interest to strive for consensus. Given the conversation at ASSC20, we are pleased to have the opportunity to address some of the nuanced topics that arose more formally, and share some of the thinking we have done since the meeting. To reflect the heterogeneity of ideas and opinions surrounding this topic, we have organized this discussion into four distinct contributions

Alice in Wonderland: The effects of body size and movement on children’s size perception and body representation in virtual reality

Previous work shows that in adults, illusory embodiment of a virtual avatar can be induced using congruent visuomotor cues. Furthermore, embodying different-sized avatars influences adults’ perception of their environment’s size. This study (N = 92) investigated whether children are also susceptible to such embodiment and size illusions. Adults and 5-year-old children viewed a first-person perspective of different-sized avatars moving either congruently or incongruently with their own body. Participants rated their feelings of embodiment over the avatar and also estimated the sizes of their body and objects in the environment. Unlike adults, children embodied the avatar regardless of visuomotor congruency. Both adults and children freely embodied different-sized avatars, and this affected their size perception in the surrounding virtual environment; they felt that objects were larger in a small body and vice versa in a large body. In addition, children felt that their body had grown in the large body condition. These findings have important implications for both our theoretical understanding of own-body representation, and our knowledge of perception in virtual environments

My body until proven otherwise: Exploring the time course of the full body illusion

Evidence from the Full Body Illusion (FBI) has shown that adults can embody full bodies which are not their own when they move synchronously with their own body or are viewed from a first-person perspective. However, there is currently no consensus regarding the time course of the illusion. Here, for the first time, we examined the effect of visuomotor synchrony (synchronous/asynchronous/no movement) on the FBI over time. Surprisingly, we found evidence of embodiment over a virtual body after five seconds in all conditions. Embodiment decreased with increased exposure to asynchronous movement, but remained high in synchronous and no movement conditions. We suggest that embodiment of a body seen from a first-person perspective is felt by default, and that embodiment can then be lost in the face of contradictory cues. These results have significant implications for our understanding of how multisensory cues contribute to embodiment

Separate processing of texture and form in the ventral stream : evidence from fMRI and visual agnosia.

Real-life visual object recognition requires the processing of more than just geometric (shape, size, and orientation) properties. Surface properties such as color and texture are equally important, particularly for providing information about the material properties of objects. Recent neuroimaging research suggests that geometric and surface properties are dealt with separately, within the lateral occipital cortex (LOC) and the collateral sulcus (CoS), respectively. Here we compared objects that either differed in aspect ratio or in surface texture only, keeping all other visual properties constant. Results on brain-intact participants confirmed that surface texture activates an area in the posterior CoS, quite distinct from the area activated by shape within LOC. We also tested two patients with visual object agnosia, one of whom (DF) performed well on the texture task but at chance on the shape task, while the other (MS) showed the converse pattern. This behavioral double dissociation was matched by a parallel neuroimaging dissociation, with activation in CoS but not LOC in patient DF, and activation in LOC but not CoS in patient MS. These data provide presumptive evidence that the areas respectively activated by shape and texture play a causally necessary role in the perceptual discrimination of these features

The Flexible Nature of Unconscious Cognition

The cognitive signature of unconscious processes is hotly debated recently. Generally, consciousness is thought to mediate flexible, adaptive and goal-directed behavior, but in the last decade unconscious processing has rapidly gained ground on traditional conscious territory. In this study we demonstrate that the scope and impact of unconscious information on behavior and brain activity can be modulated dynamically on a trial-by-trial basis. Participants performed a Go/No-Go experiment in which an unconscious (masked) stimulus preceding a conscious target could be associated with either a Go or No-Go response. Importantly, the mapping of stimuli onto these actions varied on a trial-by-trial basis, preventing the formation of stable associations and hence the possibility that unconscious stimuli automatically activate these control actions. By eliminating stimulus-response associations established through practice we demonstrate that unconscious information can be processed in a flexible and adaptive manner. In this experiment we show that the same unconscious stimulus can have a substantially different effect on behavior and (prefrontal) brain activity depending on the rapidly changing task context in which it is presented. This work suggests that unconscious information processing shares many sophisticated characteristics (including flexibility and context-specificity) with its conscious counterpart

Preservation of Auditory P300-Like Potentials in Cortical Deafness

The phenomenon of blindsight has been largely studied and refers to residual abilities of blind patients without an acknowledged visual awareness. Similarly, “deaf hearing” might represent a further example of dissociation between detection and perception of sounds