101 research outputs found
Either or neither, but not both : locating the effects of masked primes
Execution of a response that has been primed by a backward-masked stimulus is inhibited (negative compatibility effect; NCE). Three experiments investigated the locus of this inhibition. Masked primes (left- or right-pointing arrows) were followed either by an arrow or a circle target. Arrow targets always required a left- or right-hand response, but the experiments differed in the response required to circles: press neither, either or both response keys (i.e. nogo, free choice and bimanual, respectively). Arrow targets showed the usual NCEs. Circle targets showed NCEs in the form of a response bias away from the primed response in the nogo and free-choice tasks; primes and targets differed on these trials, ruling out a perceptual explanation of the NCE. The bimanual task showed no such bias, suggesting that the NCE is located at a level of abstract response codes rather than specific muscle commands
The relationship between reversed masked priming and the tri-phasic pattern of the lateralised readiness potential.
One of the potential explanations for negative compatibility effects (NCE) in subliminal motor priming tasks has been perceptual prime-target interactions. Here, we investigate whether the characteristic tri-phasic LRP pattern associated with the NCE is caused by these prime-target interactions. We found that both the prime-related phase and the critical reversal phase remain present even on trials where the target is omitted, confirming they are elicited by the prime and mask, not by prime-target interactions. We also report that shape and size of the reversal phase are associated with response speed, consistent with a causal role for the reversal for the subsequent response latency. Additionally, we analysed sequential modulation of the NCE by previous conflicting events, even though such conflict is subliminal. In accordance with previous literature, this modulation is small but significant
Effects of stimulus duration on audio-visual synchrony perception
The integration of visual and auditory inputs in the human brain occurs only if the components are perceived in temporal proximity, that is, when the intermodal time difference falls within the so-called subjective synchrony range. We used the midpoint of this range to estimate the point of subjective simultaneity (PSS). We measured the PSS for audio-visual (AV) stimuli in a synchrony judgment task, in which subjects had to judge a given AV stimulus using three response categories (audio first, synchronous, video first). The relevant stimulus manipulation was the duration of the auditory and visual components. Results for unimodal auditory and visual stimuli have shown that the perceived onset shifts to relatively later positions with increasing stimulus duration. These unimodal shifts should be reflected in changing PSS values, when AV stimuli with different durations of the auditory and visual components are used. The results for 17 subjects showed indeed a significant shift of the PSS for different duration combinations of the stimulus components. Because the shifts were approximately equal for duration changes in either of the components, no net shift of the PSS was observed as long as the durations of the two components were equal. This result indicates the need to appropriately account for unimodal timing effects when quantifying intermodal synchrony perceptio
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
Disentangling neural processing of masked and masking stimulus by means of event-related contralateral – ipsilateral differences of EEG potentials
In spite of the excellent temporal resolution of event-related EEG potentials
(ERPs), the overlapping potentials evoked by masked and masking stimuli are hard
to disentangle. However, when both masked and masking stimuli consist of pairs
of relevant and irrelevant stimuli, one left and one right from fixation, with
the side of the relevant element varying between pairs, effects of masked and
masking stimuli can be distinguished by means of the contralateral preponderance
of the potentials evoked by the relevant elements, because the relevant elements
may independently change sides in masked and masking stimuli. Based on a
reanalysis of data from which only selected contralateral-ipsilateral effects
had been previously published, the present contribution will provide a more
complete picture of the ERP effects in a masked-priming task. Indeed, effects
evoked by masked primes and masking targets heavily overlapped in conventional
ERPs and could be disentangled to a certain degree by contralateral-ipsilateral
differences. Their major component, the N2pc, is interpreted as indicating
preferential processing of stimuli matching the target template, which process
can neither be identified with conscious perception nor with shifts of spatial
attention. The measurements showed that the triggering of response preparation
by the masked stimuli did not depend on their discriminability, and their
priming effects on the processing of the following target stimuli were
qualitatively different for stimulus identification and for response
preparation. These results provide another piece of evidence for the
independence of motor-related and perception-related effects of masked
stimuli
A modal theorem-preserving translation of a class of three-valued logics of incomplete information
International audienceThere are several three-valued logical systems that form a scattered landscape, even if all reasonable connectives in three-valued logics can be derived from a few of them. Most papers on this subject neglect the issue of the relevance of such logics in relation with the intended meaning of the third truth-value. Here, we focus on the case where the third truth-value means unknown, as suggested by Kleene. Under such an understanding, we show that any truth-qualified formula in a large range of three-valued logics can be translated into KD as a modal formula of depth 1, with modalities in front of literals only, while preserving all tautologies and inference rules of the original three-valued logic. This simple information logic is a two-tiered classical propositional logic with simple semantics in terms of epistemic states understood as subsets of classical interpretations. We study in particular the translations of Kleene, Gödel, ᴌukasiewicz and Nelson logics. We show that Priest’s logic of paradox, closely connected to Kleene’s, can also be translated into our modal setting, simply by exchanging the modalities possible and necessary. Our work enables the precise expressive power of three-valued logics to be laid bare for the purpose of uncertainty management
Effects of auditory stimulus intensity on response force in simple, go/no-go, and choice RT tasks
Optimal perceived timing: integrating sensory information with dynamically updated expectations
The environment has a temporal structure, and knowing when a stimulus will appear translates into increased perceptual performance. Here we investigated how the human brain exploits temporal regularity in stimulus sequences for perception. We find that the timing of stimuli that occasionally deviate from a regularly paced sequence is perceptually distorted. Stimuli presented earlier than expected are perceptually delayed, whereas stimuli presented on time and later than expected are perceptually accelerated. This result suggests that the brain regularizes slightly deviant stimuli with an asymmetry that leads to the perceptual acceleration of expected stimuli. We present a Bayesian model for the combination of dynamically-updated expectations, in the form of a priori probability of encountering future stimuli, with incoming sensory information. The asymmetries in the results are accounted for by the asymmetries in the distributions involved in the computational process
On the discrepant results in synchrony judgment and temporal-order judgment tasks: a quantitative model
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