131 research outputs found
The accumulation of evidence for decision-making and confidence
No full textThis project examines how the accumulation of noisy sensory evidence affects both decisions and confidence in those decisions.
This project was created by Tarryn Balsdon, however, the project is a collaboration with Dr Pascal Mamassian and Dr Valentin Wyart, who are the senior authors and sourced the funding for the project
Fork of The accumulation of evidence for decision-making and confidence
No full textData and code for the pre-registered project.
This is soon to be published as:
Balsdon, T., Wyart, V., & Mamassian, P. (2020) Confidence controls perceptual evidence accumulation. Nature Communications.
Please cite this paper with any use of the materials made freely available here
Fork of The accumulation of evidence for decision-making and confidence
No full textData and code for the pre-registered project.
This is soon to be published as:
Balsdon, T., Wyart, V., & Mamassian, P. (2020) Confidence controls perceptual evidence accumulation. Nature Communications.
Please cite this paper with any use of the materials made freely available here
Absolute and relative blindsight
No full textThe concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight
Computing perceived gaze direction
No full textIn this thesis, I will briefly introduce the perception of others’ gaze direction as an integral part of social cognition. I will then discuss experimental findings that underpin our understanding of how the perception of gaze direction is achieved in the human brain. The main body of this thesis presents a number of experiments that were conducted to further address how a variety of sensory cues are weighted in the computation of perceived gaze direction. Chapter One examines a bias-minimising measure of the effect of head orientation on perceived gaze direction. This measure produced pronounced
differences from previous measures, which is explored further in Chapter Two. The findings of Chapter Two suggest that these differences are not the result of some perceptual artefact concerning differences in stimulus presentation, but rather in the way observers are using cues to gaze direction depending on whether observers are taking an allocentric or egocentric perspective. This could be the result of integrating nondirectional cues to direct gaze when making judgements of whether gaze is direct. The use of one such cue, the circularity of the pupil/iris, is examined in Chapter Three. Although it
is found that the circularity cue is not driving the task dependent differences in the effect of head orientation on perceived gaze direction, the results suggest a further, computational, difference in the integration of information for allocentric (directional) and egocentric (non-directional) gaze judgements. This difference is explored in Chapter Four, where a double judgements procedure is used to elucidate the computational differences between detecting direct gaze and identifying gaze direction, and the implications of this difference on perceived gaze direction. Finally, Chapter Five accounts for perceived gaze direction, which can differ from veridically presented gaze direction, in objective measures of the range of gaze deviations the observer is willing to accept as directed at them. These experiments suggest that observers are able to flexibly integrate cues to gaze direction depending on the judgement to be made, and that consideration of decision-making
factors is important in understanding the perception of gaze direction from observers’ responses in an experimental setting
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