Date of Award


Degree Type

UG Dissertation

First Advisor

Prof. Alan Lee, Lap Fai


Perceptual confidence has been found to correlate with task performance in general, and is believed to be independent of stimulus features. However, certain stimulus feature could induce a subjective sense of uncertainty, which could potentially influence confidence judgments beyond task performance. The present studies aimed at assessing the effects of the ambiguity of local motion signals on perceptual confidence on a global-motion task. Participants first discriminated the global motion directions of two multiple-aperture, global-motion patterns, one generated using multiple Gabor elements and the other using multiple Plaid elements. They then performed a two-interval, forced-choice confidence task by choosing which of the two perceptual responses they were more confident in being correct. In Experiment 1, when perceptual performance was controlled by varying coherence, we found that participants chose plaids more often than Gabors, even with perceptual performance matched between the two patterns. In Experiment 2, when perceptual performance was controlled by varying luminance contrast of noisy pixels in every motion frame, such “plaid preference” in confidence bias was significantly weakened.

Besides, there has been numerous studies on visual perception of autistic individuals. But not many of them has looked into the relationship between their metacognition and perceptual judgement. This study aimed at assessing the relationship between the autistic trait tendency and metacognitive process about one’s perceptual performance. Our results show that, at the same level of objective task performance, subject perceptual confidence depends on both the ambiguity of local motion signals and the type of noise. Our results also shows that there is an association between the subject perceptual confidence and the autistic trait tendency.



Recommended Citation

Lam, W. W. A. (2019). How visual confidence on global motion is affected by local motion ambiguity and type of motion noise, and its correlation with autistic trait tendency? (UG dissertation, Lingnan University, Hong Kong). Retrieved from

Included in

Sociology Commons