At the mercy of prior entry: Prior entry induced by invisible primes is not susceptible to current intentions

We prefer what we fear: A response preference bias mimics attentional capture in spider fear

The extent to which emotionally significant stimuli capture visual attention remains elusive because a preference for reporting or choosing emotionally significant stimuli could mimic attentional capture by these stimuli. We conducted two prior-entry experiments to disentangle whether phobic and fear-relevant stimuli capture attention or merely produce a response bias in spider-fearful participants. Prior entry denotes the effect that attended stimuli are perceived earlier than unattended stimuli as indicated by temporal order judgments. We presented phobic (spiders), fear-relevant (snakes) and neutral stimuli in pairs with varying temporal onset. The participants' task was to indicate which stimulus was presented first (Experiment 1) or second (Experiment 2). In the first experiment, spider-fearful but not control participants indicated that they had perceived spiders as occurring earlier in time, suggesting a prior-entry effect for spiders in this group. But surprisingly, in the second experiment, spider-fearful participants indicated more frequently that they had seen spiders as being presented second. This finding rules out a genuine prior-entry effect and instead suggests a strong preference for the response option associated with the feared animal. This response bias may result from a hypervigilance toward the feared stimulus and contribute to maintaining avoidance behavior in individuals with specific phobias.

Differences between endogenous attention to spatial locations and sensory modalities

Vibell et al. (J Cogn Neurosci 19:109-120, 2007) reported that endogenously attending to a sensory modality (vision or touch) modulated perceptual processing, in part, by the relative speeding-up of neural activation (i.e., as a result of prior entry). However, it was unclear whether it was the fine temporal discrimination required by the temporal-order judgment task that was used, or rather, the type of attentional modulation (spatial locations or sensory modalities) that was responsible for the shift in latencies that they observed. The present study used a similar experimental design to evaluate whether spatial attention would also yield similar latency effects suggestive of prior entry in the early visual P1 potentials. Intriguingly, while the results demonstrate similar neural latency shifts attributable to spatial attention, they started at a somewhat later stage than seen in Vibell et al.'s study. These differences are consistent with different neural mechanisms underlying attention to a specific sensory modality versus to a spatial location.

Introspective access to implicit shifts of attention

Literature in metacognition has systematically rejected the possibility of introspective access to complex cognitive processes. This situation derives from the difficulty of experimentally manipulating cognitive processes while abiding by the two contradictory constraints. First, participants must not be aware of the experimental manipulation, otherwise they run the risk of incorporating their knowledge of the experimental manipulation in some rational elaboration. Second, we need an external, third person perspective evidence that the experimental manipulation did impact some relevant cognitive processes. Here, we study introspection during visual searches, and we try to overcome the above dilemma, by presenting a barely visible, "pre-conscious" cue just before the search array. We aim at influencing the attentional guidance of the search processes, while participants would not notice that fact. Results show that introspection of the complexity of a search process is driven in part by subjective access to its attentional guidance.

Involuntary attentional orienting in the absence of awareness speeds up early sensory processing

A long-standing controversy in the field of human neuroscience has revolved around the question whether attended stimuli are processed more rapidly compared to unattended stimuli. We conducted two event-related potential (ERP) experiments employing a temporal order judgment procedure in order to assess whether involuntary attention accelerates sensory processing, as indicated by latency modulations of early visual ERP components. A non-reportable exogenous cue could precede the first target with equal probability at the same (compatible) or opposite (incompatible) location. The use of non-reportable cues promoted automatic, bottom-up attentional capture, and ensured the elimination of any confounds related to the use of stimulus features that are common to both cue and target. Behavioral results confirmed involuntary exogenous orienting towards the unaware cue. ERP results showed that the N1pc, an electrophysiological measure of attentional orienting, was smaller and peaked earlier in compatible as opposed to incompatible trials, indicating cue-dependent changes in magnitude and speed of first target processing in extrastriate visual areas. Complementary Bayesian analysis confirmed the presence of this effect regardless of whether participants were actively looking for the cue (Experiment 1) or were not informed of it (Experiment 2), indicating purely automatic, stimulus-driven orienting mechanisms.

Unconscious vision and executive control: how unconscious processing and conscious action control interact

Research on unconscious or unaware vision has demonstrated that unconscious processing can be flexibly adapted to the current goals of human agents. The present review focuses on one area of research, masked visual priming. This method uses visual stimuli presented in a temporal sequence to lower the visibility of one of these stimuli. In this way, a stimulus can be masked and even rendered invisible. Despite its invisibility, a masked stimulus if used as a prime can influence a variety of executive functions, such as response activation, semantic processing, or attention shifting. There are also limitations on the processing of masked primes. While masked priming research demonstrates the top-down dependent usage of unconscious vision during task-set execution it also highlights that the set-up of a new task-set depends on conscious vision as its input. This basic distinction captures a major qualitative difference between conscious and unconscious vision.

No prior entry for threat-related faces: evidence from temporal order judgments

Previous research showed that threat-related faces, due to their intrinsic motivational relevance, capture attention more readily than neutral faces. Here we used a standard temporal order judgment (TOJ) task to assess whether negative (either angry or fearful) emotional faces, when competing with neutral faces for attention selection, may lead to a prior entry effect and hence be perceived as appearing first, especially when uncertainty is high regarding the order of the two onsets. We did not find evidence for this conjecture across five different experiments, despite the fact that participants were invariably influenced by asynchronies in the respective onsets of the two competing faces in the pair, and could reliably identify the emotion in the faces. Importantly, by systematically varying task demands across experiments, we could rule out confounds related to suboptimal stimulus presentation or inappropriate task demands. These findings challenge the notion of an early automatic capture of attention by (negative) emotion. Future studies are needed to investigate whether the lack of systematic bias of attention by emotion is imputed to the primacy of a non-emotional cue to resolve the TOJ task, which in turn prevents negative emotion to exert an early bottom-up influence on the guidance of spatial and temporal attention.

Attention and the speed of information processing: posterior entry for unattended stimuli instead of prior entry for attended stimuli

Why are nearly simultaneous stimuli frequently perceived in reversed order? The origin of errors in temporal judgments is a question older than experimental psychology itself. One of the earliest suspects is attention. According to the concept of prior entry, attention accelerates attended stimuli; thus they have "prior entry" to perceptive processing stages, including consciousness. Although latency advantages for attended stimuli have been revealed in psychophysical studies many times, these measures (e.g. temporal order judgments, simultaneity judgments) cannot test the prior-entry hypothesis completely. Since they assess latency differences between an attended and an unattended stimulus, they cannot distinguish between faster processing of attended stimuli and slower processing of unattended stimuli. Therefore, we present a novel paradigm providing separate estimates for processing advantages respectively disadvantages of attended and unattended stimuli. We found that deceleration of unattended stimuli contributes more strongly to the prior-entry illusion than acceleration of attended stimuli. Thus, in the temporal domain, attention fulfills its selective function primarily by deceleration of unattended stimuli. That means it is actually posterior entry, not prior entry which accounts for the largest part of the effect.