10 research outputs found
Does the Theist Have an Epistemic Advantage over the Atheist?: Plantinga and Descartes on Theism, Atheism, and Skepticism
Being More Realistic About Reasons: On Rationality and Reasons Perspectivism
This paper looks at whether it is possible to unify the
requirements of rationality with the demands of normative
reasons. It might seem impossible to do because one depends
upon the agent’s perspective and the other upon features of
the situation. Enter Reasons Perspectivism. Reasons
perspectivists think they can show that rationality does consist
in responding correctly to reasons by placing epistemic
constraints on these reasons. They think that if normative
reasons are subject to the right epistemic constraints, rational
requirements will correspond to the demands generated by
normative reasons. While this proposal is prima facie plausible,
it cannot ultimately unify reasons and rationality. There is no
epistemic constraint that can do what reasons perspectivists
would need it to do. Some constraints are too strict. The rest
are too slack. This points to a general problem with the
reasons-first program. Once we recognize that the agent’s
epistemic position helps determine what she should do, we
have to reject the idea that the features of the agent’s situation
can help determine what we should do. Either rationality
crowds out reasons and their demands or the reasons will make
unreasonable demands
On the Role of Attention in Binocular Rivalry: Electrophysiological Evidence
During binocular rivalry visual consciousness fluctuates between two dissimilar monocular images. We investigated the role of attention in this phenomenon by comparing event-related potentials (ERPs) when binocular-rivalry stimuli were attended with when they were unattended. Stimuli were dichoptic, orthogonal gratings that yielded binocular rivalry and dioptic, identically oriented gratings that yielded binocular fusion. Events were all possible orthogonal changes in orientation of one or both gratings. We had two attention conditions: In the attend-to-grating condition, participants had to report changes in perceived orientation, focussing their attention on the gratings. In the attend-to-fixation condition participants had to report changes in a central fixation target, taking attention away from the gratings. We found, surprisingly, that attending to rival gratings yielded a smaller ERP component (the N1, from 160–210 ms) than attending to the fixation target. To explain this paradoxical effect of attention, we propose that rivalry occurs in the attend-to-fixation condition (we found an ERP signature of rivalry in the form of a sustained negativity from 210–300 ms) but that the mechanism processing the stimulus changes is more adapted in the attend-to-grating condition than in the attend-to-fixation condition. This is consistent with the theory that adaptation gives rise to changes of visual consciousness during binocular rivalry
Do early neural correlates of visual consciousness show the oblique effect? A binocular rivalry and event-related potential study
Predicting visual consciousness electrophysiologically from intermittent binocular rivalry
Purpose: We sought brain activity that predicts visual consciousness.
Methods: We used electroencephalography (EEG) to measure brain activity to a 1000-ms display of sine-wave gratings, oriented vertically in one eye and horizontally in the other. This display yields binocular rivalry: irregular alternations in visual consciousness between the images viewed by the eyes. We replaced both gratings with 200 ms of darkness, the gap, before showing a second display of the same rival gratings for another 1000 ms. We followed this by a 1000-ms mask then a 2000- ms inter-trial interval (ITI). Eleven participants pressed keys after the second display in numerous trials to say whether the orientation of the visible grating changed from before to after the gap or not. Each participant also responded to numerous non-rivalry trials in which the gratings had identical orientations for the two eyes and for which the orientation of both either changed physically after the gap or did not.
Results: We found that greater activity from lateral occipital-parietal-temporal areas about 180 ms after initial onset of rival stimuli predicted a change in visual consciousness more than 1000 ms later, on re-presentation of the rival stimuli. We also found that less activity from parietal, central, and frontal electrodes about 400 ms after initial onset of rival stimuli predicted a change in visual consciousness about 800 ms later, on re-presentation of the rival stimuli. There was no such predictive activity when the change in visual consciousness occurred because the stimuli changed physically.
Conclusion: We found early EEG activity that predicted later visual consciousness. Predictive activity 180 ms after onset of the first display may reflect adaption of the neurons mediating visual consciousness in our displays. Predictive activity 400 ms after onset of the first display may reflect a less-reliable brain state mediating visual consciousness