Previous research has shown that subliminally presented stimuli accelerate or delay responses afforded by supraliminally presented stimuli. Our experiments extend these findings by showing that unconscious stimuli even affect free choices between responses. Thus, actions that are phenomenally experienced as freely chosen are influenced without the actor becoming aware of the manipulation. However, the unconscious influence is limited to a response bias, as participants chose the primed response only in up to 60% of the trials. LRP data in free choice (...) trials indicate that the prime was not ineffective in trials in which participants chose the non-primed response as then it delayed performance of the incongruently primed response. (shrink)

When the stored representation of the meaning of a stimulus is accessed through the processing of a sensory input it is maintained in an activated state for a certain amount of time that allows for further processing. This semantic activation is generally accompanied by conscious identification, which can be demonstrated by the ability of a person to perform discriminations on the basis of the meaning of the stimulus. The idea that a sensory input can give rise to semantic activation without (...) concomitant conscious identification was the central thesis of the controversial research in subliminal perception. Recently, new claims for the existence of such phenomena have arisen from studies in dichotic listening, parafoveal vision, and visual pattern masking. Because of the fundamental role played by these types of experiments in cognitive psychology, the new assertions have raised widespread interest. (shrink)

Shapes that are rendered invisible through backward masking are still able to influence motor responses: this is called masked priming. Yet it is unknown whether this influence is on the control of ongoing action, or whether it merely influences the initiation of an already-programmed action. We modified a masked priming procedure such that the critical prime-mask sequence was displayed during the execution of an already-initiated goal-directed pointing movement. Psychophysical tests of prime visibility indicated that the identity of the prime shapes (...) were not accessible to participants for conscious report. Yet detailed kinematic analysis of the finger in motion revealed that masked primes had an influence on the pointing trajectories within 277 ms of their appearance, 56 ms earlier than the trajectory deviations observed in response to the visible masks. These results indicate that subliminal shapes can indeed influence the control of ongoing motor activity. (shrink)

Do studies of perception without awareness and studies of perception without attention address a similar underlying concept of awareness? To answer this question, we compared qualitative differences in performance across variations in stimulus quality with qualitative differences in performance across variations in the direction of attention . The qualitative differences were based on three different phenomena: Stroop priming, false recognition, and exclusion failure. In all cases, variations in stimulus quality and variations in the direction of attention led to parallel findings. (...) These results suggest that perception with and without awareness and perception with and without attention are equivalent ways of describing the same underlying process distinction. (shrink)

Subjects classified visible 2-digit numbers as larger or smaller than 55. Target numbers were preceded by masked 2-digit primes that were either congruent (same relation to 55) or incongruent. Experiments 1 and 2 showed prime congruency effects for stimuli never included in the set of classified visible targets, indicating subliminal priming based on long-term semantic memory. Experiments 2 and 3 went further to demonstrate paradoxical unconscious priming effects resulting from task context. For example, after repeated practice classifying 73 as larger (...) than 55, the novel masked prime 37 paradoxically facilitated the “larger” response. In these experiments task context could induce subjects to unconsciously process only the leftmost masked prime digit, only the rightmost digit, or both independently. Across 3 experiments, subliminal priming was governed by both task context and long-term semantic memory. (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)