Unconscious Perception

In a recent paper in Psychological Science, Kouider and Dupoux reported obtaining unconscious Stroop priming only when subjects had partial awareness of the masked distractor words . Kouider and Dupoux conjectured that semantic priming occurs only when such partial awareness is present. The present experiments tested this conjecture in an affective categorization priming task that differed from Kouider and Dupoux’s in using masked distractors that subjects had practiced earlier as visible words. Experiment 1 showed priming from practiced words when subjects (...) had no partial awareness of those words. Experiment 2 showed that, in the absence of partial awareness, practiced words yielded priming but not-practiced words did not. Experiment 3 corroborated Experiment 1 and 2s results using a different test of partial awareness. These results suggest that unconscious processing of subword elements drives masked semantic priming by practiced words. (shrink)

In vision research metacontrast masking is a widely used technique to reduce the visibility of a stimulus. Typically, studies attempt to reveal general principles that apply to a large majority of participants and tend to omit possible individual differences. The neural plasticity of the visual system, however, entails the potential capability for individual differences in the way observers perform perceptual tasks. We report a case of perceptual learning in a metacontrast masking task that leads to the enhancement of two types (...) of adult human observers despite identical learning conditions. In a priming task both types of observers exhibited the same priming effects, which were insensitive to learning. Findings suggest that visual processing of target stimuli in the metacontrast masking task is based on neural levels with sufficient plasticity to enable the development of two types of observers, which do not contribute to processing of target stimuli in the priming task. (shrink)

In metacontrast masking target visibility is modulated by the time until a masking stimulus appears. The effect of this temporal delay differs across participants in such a way that individual human observers’ performance shows distinguishable types of masking functions which remain largely unchanged for months. Here we examined whether individual differences in masking functions depend on different response criteria in addition to differences in discrimination sensitivity. To this end we reanalyzed previously published data and conducted a new experiment for further (...) data analyses. Our analyses demonstrate that a distinction of masking functions based on the type of masking stimulus is superior to a distinction based on the target–mask congruency. Individually different masking functions are based on individual differences in discrimination sensitivities and in response criteria. Results suggest that individual differences in metacontrast masking result from individually different criterion contents. (shrink)

Contemporary studies in unconscious cognition are essentially founded on dissociation, i.e., on how it dissociates with respect to conscious mental processes and representations. This is claimed to be in so many and diverse ways that one is often lost in dissociation. In order to reduce this state of confusion we here carry out two major tasks: based on the central distinction between cognitive processes and representations, we identify and isolate the main dissociation paradigms; we then critically analyze their key tenets (...) and reported findings. (shrink)

Three experiments examined the role of response criteria in a masked semantic priming paradigm using an exclusion task. Experiment 1 used on-line prime-report and exclusion instructions in which participants were told to avoid completing a word stem with a word related to a prime flashed for 0, 38 or 212 ms. Semantic priming was significant in the items analysis, but was moderated by peoples’ ability to report the prime in the participant analysis. Prime-report thresholds in Experiment 2 were made more (...) liberal by instructing participants to guess on every trial. Prime-report increased from Experiment 1 as exclusion failures were eliminated. Experiment 3 clarified the relationship between awareness and prime identification using an on-line measure of confidence and different liberal prime report instructions. The current findings suggest that the ability to act upon and report information in a masked prime is determined by a variable response criterion, which can be manipulated as an independent variable. (shrink)

Relationalism holds that perceptual experiences are relations between subjects and perceived objects. But much evidence suggests that perceptual states can be unconscious. We argue here that unconscious perception raises difficulties for relationalism. Relationalists would seem to have three options. First, they may deny that there is unconscious perception or question whether we have sufficient evidence to posit it. Second, they may allow for unconscious perception but deny that the relationalist analysis applies to it. Third, they may offer a relationalist explanation (...) of unconscious perception. We argue that each of these strategies is questionable. (shrink)

We propose a new masking technique for masking word stimuli. Drawing on the phenomena of metacontrast and paracontrast, we alternately presented two prime displays of the same word with the background color in one display matching the font color in the other display and vice versa. The sequence of twenty alterations was sandwich-masked by structure masks. Using this masking technique, we conducted evaluative priming experiments with positive and negative target and prime words. Significant priming effects were found – for primes (...) and targets drawn from the same as well as from different word sets. Priming effects were independent of prime discrimination performance in direct tests and they were still significant after the sample was restricted to those participants who showed random responding in the direct test. (shrink)

Research on perception without awareness has provoked strong emotional responses from individuals within and outside the scientific community, due in part to the perceived potential for abuse of subliminal techniques. In this paper, four basic issues regarding the use of subliminal techniques for propaganda purposes are discussed: whether exposure to subliminal stimuli can produce significant, predictable changes in affect, cognition and behavior; whether these effects are robust and powerful enough to make the use of subliminal techniques for propaganda purposes feasible; (...) whether the effects of subliminal stimulation are stable over time; and whether subliminal influences can be resisted by unwilling subjects. Research suggests that exposure to simple drive-or affect-related subliminal stimuli can produce ecologically significant, temporally stable changes in attitudes and behavior, and therefore may have potential for use as propaganda tools. Implications of these findings for our understanding of the mechanisms underlying subliminal perception are discussed. Technical problems which would need to be addressed before subliminal propaganda techniques could be employed are also discussed. Ethical issues raised by the use of covert attitude and behavior manipulation techniques are addressed. (shrink)

In his analysis of subliminal perception research, Erdelyi documented two important phenomena: subchance perception and temporal variability in stimulus availability and accessibility. This Commentary addresses three issues raised by Erdelyi's review: the importance of distinguishing “micro” from “macro” temporal shifts; the need to analyze perception without awareness data at the level of the individual as well as the group; and parallels between the dissociations associated with neuroclinical phenomena and those observed in patients with certain forms of personality pathology. Continued integration (...) of laboratory findings with in vivo observations of clinical syndromes will yield a more cohesive and heuristic approach to the study of implicit mental states. (shrink)

This new edition uses the technique of visual masking to explore temporal aspects of conscious and unconscious processes down to a resolution in the...

Using a metacontrast masking paradigm, prior studies have shown that a target’s color information and form information, can be processed without awareness and that unconscious color processing occurs at early, wavelength-dependent levels in the cortical information processing hierarchy. Here we used a combination of paracontrast and metacontrast masking techniques to explore unconscious color and form priming effects produced by blue, green, and neutral stimuli. We found that color priming in normal observers is significantly reduced when an additional paracontrast mask precedes (...) the target at optimal masking SOAs. However, no reduction of form-priming effects was obtained at similar optimal paracontrast SOAs. We conclude that unconscious color priming depends on an early, wavelength- or stimulus-dependent response of color neurons located at early cortical levels whereas unconscious form priming occurs at later levels. (shrink)

Visual stimuli as well as transcranial magnetic stimulation can be used: to suppress the visibility of a target and to recover the visibility of a target that has been suppressed by another mask. Both types of stimulation thus provide useful methods for studying the microgenesis of object perception. We first review evidence of similarities between the processes by which a TMS mask and a visual mask can either suppress the visibility of targets or recover such suppressed visibility. However, we then (...) also point out a significant difference that has important implications for the study of the time course of unconscious and conscious visual information processing and for theoretical accounts of the processes involved. We present evidence and arguments showing: that visual masking techniques, by revealing more detailed aspects of target masking and target recovery, support a theoretical approach to visual masking and visual perception that must take into account activities in two separate neural channels or processing streams and, as a corollary, that at the current stage of methodological sophistication visual masks, by acting in more highly specifiable ways on these pathways, provide information about the microgenesis of form perception not available with TMS masks. (shrink)