Barack Obama Blindness (BOB): Absence of Visual Awareness to a Single Object

In two experiments, we evaluated whether a perceiver’s prior expectations could alone obliterate his or her awareness of a salient visual stimulus. To establish expectancy, observers first made a demanding visual discrimination on each of three baseline trials. Then, on a fourth, critical trial, a single, salient and highly visible object appeared in full view at the center of the visual field and in the absence of any competing visual input. Surprisingly, fully half of the participants were unaware of the solitary object in front of their eyes. Dramatically, observers were blind even when the only stimulus on display was the face of U.S. President Barack Obama. We term this novel, counter intuitive phenomenon, Barack Obama Blindness (BOB). Employing a method that rules out putative memory effects by probing awareness immediately after presentation of the critical stimulus, we demonstrate that the BOB effect is a true failure of conscious vision

Measuring Perceptual Consciousness

Conscious perception is typically assessed with either objective or subjective measures (Seth et al.,2008). Measures are considered objective if conscious perception is estimated from performancein a discrimination task; inability to discriminate between stimuli is taken as evidence thatparticipants had no conscious perception (Hannula et al., 2005). Measures are considered subjectiveif participants report their visual experience on each trial (Sergent and Dehaene, 2004; Del Culet al., 2007). One type of subjective measures consists of metacognitivejudgments; the relationshipbetween metacognition and perceptual awareness is a matter ofdebate (Fleming and Lau, 2014;Jachs et al., 2015) and I will not discuss these measures further. Likewise, I will not discuss post-decision wagering approaches as they are affected by the participants’ risk aversion (Schurger andSher, 2008). Proponents of subjective measures stress that objective measures (discrimination)provide only task performance and are not suitable for capturing visual experience (Lau, 2008).The major objection against subjective measures is contamination by response bias. Becauseit has been argued that participants can perform discrimination in the absence of perceptualawareness, many researchers currently favor subjective measures. In this paper, I show thatobjective measures (discrimination) and subjective measures (detection) are similar and bothmeasure task performance. I further propose that task performance can be used as a valid measureof conscious perception

Unconscious Priming Requires Early Visual Cortex at Specific Temporal Phases of Processing

Although examples of unconscious shape priming have been well documented, whether such priming requires early visual cortex (V1/V2) has not been established. In the current study, we used TMS of V1/V2 at varying temporal intervals to suppress the visibility of preceding shape primes while the interval between primes and targets was kept constant. Our results show that, although conscious perception requires V1/V2, unconscious priming can occur without V1/V2 at an intermediate temporal interval but not at early (5–25 msec) or later (65–125 msec) stages of processing. Because the later time window of unconscious priming suppression has been proposed to interfere with feedback processing, our results further suggest that feedback processing is also essential for unconscious priming and may not be a sufficient condition for conscious vision

Working Memory and Consciousness: the current state of play

Working memory, an important posit in cognitive science, allows one to temporarily store and manipulate information in the service of ongoing tasks. Working memory has been traditionally classified as an explicit memory system – that is, as operating on and maintaining only consciously perceived information. Recently, however, several studies have questioned this assumption, purporting to provide evidence for unconscious working memory. In this paper, we focus on visual working memory and critically examine these studies as well as studies of unconscious perception that seem to provide indirect evidence for unconscious working memory. Our analysis indicates that current evidence does not support an unconscious working memory store, though we offer independent reasons to think that working memory may operate on unconsciously perceived information

Measuring Perceptual Consciousness

Conscious perception is typically assessed with either objective or subjective measures (Seth et al.,2008). Measures are considered objective if conscious perception is estimated from performancein a discrimination task; inability to discriminate between stimuli is taken as evidence thatparticipants had no conscious perception (Hannula et al., 2005). Measures are considered subjectiveif participants report their visual experience on each trial (Sergent and Dehaene, 2004; Del Culet al., 2007). One type of subjective measures consists of metacognitivejudgments; the relationshipbetween metacognition and perceptual awareness is a matter ofdebate (Fleming and Lau, 2014;Jachs et al., 2015) and I will not discuss these measures further. Likewise, I will not discuss post-decision wagering approaches as they are affected by the participants’ risk aversion (Schurger andSher, 2008). Proponents of subjective measures stress that objective measures (discrimination)provide only task performance and are not suitable for capturing visual experience (Lau, 2008).The major objection against subjective measures is contamination by response bias. Becauseit has been argued that participants can perform discrimination in the absence of perceptualawareness, many researchers currently favor subjective measures. In this paper, I show thatobjective measures (discrimination) and subjective measures (detection) are similar and bothmeasure task performance. I further propose that task performance can be used as a valid measureof conscious perception

A MecA Paralog, YpbH, Binds ClpC, Affecting both Competence and Sporulation

ComK, the master regulator of competence, is degraded by the general stress-related protease ClpCP but must be targeted to this protease by binding to the adapter protein MecA. The genome of Bacillus subtilis contains a paralog of mecA, ypbH. We show in the present study that YpbH, like MecA, binds ClpC and that its elimination or overproduction affects competence and sporulation