50 research outputs found
Neuro-cognitive mechanisms of conscious and unconscious visual perception: From a plethora of phenomena to general principles
Psychological and neuroscience approaches have promoted much progress in
elucidating the cognitive and neural mechanisms that underlie phenomenal visual
awareness during the last decades. In this article, we provide an overview of
the latest research investigating important phenomena in conscious and
unconscious vision. We identify general principles to characterize conscious and
unconscious visual perception, which may serve as important building blocks for
a unified model to explain the plethora of findings. We argue that in particular
the integration of principles from both conscious and unconscious vision is
advantageous and provides critical constraints for developing adequate
theoretical models. Based on the principles identified in our review, we outline
essential components of a unified model of conscious and unconscious visual
perception. We propose that awareness refers to consolidated
visual representations, which are accessible to the entire brain and therefore
globally available. However, visual awareness not only depends
on consolidation within the visual system, but is additionally the result of a
post-sensory gating process, which is mediated by higher-level cognitive control
mechanisms. We further propose that amplification of visual representations by
attentional sensitization is not exclusive to the domain of conscious
perception, but also applies to visual stimuli, which remain unconscious.
Conscious and unconscious processing modes are highly interdependent with
influences in both directions. We therefore argue that exactly this
interdependence renders a unified model of conscious and unconscious visual
perception valuable. Computational modeling jointly with focused experimental
research could lead to a better understanding of the plethora of empirical
phenomena in consciousness research
Dos and don’ts in response priming research
Response priming is a well-understood but sparsely employed paradigm in cognitive
science. The method is powerful and well-suited for exploring early visuomotor
processing in a wide range of tasks and research fields. Moreover, response
priming can be dissociated from visual awareness, possibly because it is based
on the first sweep of feedforward processing of primes and targets. This makes
it a theoretically interesting device for separating conscious and unconscious
vision. We discuss the major opportunities of the paradigm and give specific
recommendations (e.g., tracing the time-course of priming in parametric
experiments). Also, we point out typical confounds, design flaws, and data
processing artifacts
Unconsciously Triggered Conflict Adaptation
In conflict tasks such as the Stroop, the Eriksen flanker or the Simon task, it is generally observed that the detection of conflict in the current trial reduces the impact of conflicting information in the subsequent trial; a phenomenon termed conflict adaptation. This higher-order cognitive control function has been assumed to be restricted to cases where conflict is experienced consciously. In the present experiment we manipulated the awareness of conflict-inducing stimuli in a metacontrast masking paradigm to directly test this assumption. Conflicting response tendencies were elicited either consciously (through primes that were weakly masked) or unconsciously (strongly masked primes). We demonstrate trial-by-trial conflict adaptation effects after conscious as well as unconscious conflict, which could not be explained by direct stimulus/response repetitions. These findings show that unconscious information can have a longer-lasting influence on our behavior than previously thought and further stretch the functional boundaries of unconscious cognition
The Spatial and Temporal Construction of Confidence in the Visual Scene
Human subjects can report many items of a cluttered field a few hundred milliseconds after stimulus presentation. This memory decays rapidly and after a second only 3 or 4 items can be stored in working memory. Here we compared the dynamics of objective performance with a measure of subjective report and we observed that 1) Objective performance beyond explicit subjective reports (blindsight) was significantly more pronounced within a short temporal interval and within specific locations of the visual field which were robust across sessions 2) High confidence errors (false beliefs) were largely confined to a small spatial window neighboring the cue. The size of this window did not change in time 3) Subjective confidence showed a moderate but consistent decrease with time, independent of all other experimental factors. Our study allowed us to asses quantitatively the temporal and spatial access to an objective response and to subjective reports
Subliminal stimuli in the near absence of attention influence top-down cognitive control
Recent research has shown that visual stimuli can influence cognitive control functions, even if subjects are unaware of the identity of the stimuli. However, in those previous studies, subjects actively attended to the location of the subliminal stimuli. Here we assessed the role of endogenous spatial attention in such paradigms. We required subjects to quickly prepare for one of two numerical judgment tasks on the basis of the direction of motion in patches of moving dots presented in cued spatial locations. We found that irrelevant motion patches presented in the uncued spatial locations also influenced task performance. Motion in the uncued patches was weak and did not affect the perception of the cued patches. Further analyses suggested that the effect of priming by the uncued stimuli was present even for subjects who could only discriminate such stimuli at chance level. Three additional experiments confirmed that subjects paid minimal attention to the uncued locations, in that the subjects could not perform simple discriminations of conjunctions of features in those locations
Subliminal Semantic Priming in Speech
Numerous studies have reported subliminal repetition and semantic priming in the visual modality. We transferred this paradigm to the auditory modality. Prime awareness was manipulated by a reduction of sound intensity level. Uncategorized prime words (according to a post-test) were followed by semantically related, unrelated, or repeated target words (presented without intensity reduction) and participants performed a lexical decision task (LDT). Participants with slower reaction times in the LDT showed semantic priming (faster reaction times for semantically related compared to unrelated targets) and negative repetition priming (slower reaction times for repeated compared to semantically related targets). This is the first report of semantic priming in the auditory modality without conscious categorization of the prime
Subliminal Semantic Priming in Speech
Numerous studies have reported subliminal repetition and semantic priming in the visual modality. We transferred this paradigm to the auditory modality. Prime awareness was manipulated by a reduction of sound intensity level. Uncategorized prime words (according to a post-test) were followed by semantically related, unrelated, or repeated target words (presented without intensity reduction) and participants performed a lexical decision task (LDT). Participants with slower reaction times in the LDT showed semantic priming (faster reaction times for semantically related compared to unrelated targets) and negative repetition priming (slower reaction times for repeated compared to semantically related targets). This is the first report of semantic priming in the auditory modality without conscious categorization of the prime