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Variability in multistable apparent motion perception

Boek - Dissertatie

Visual perception is not merely the result of stimuli being processed by passive observers. Our perceptual system actively disambiguates and interprets the information it receives from our eyes. Multistable perception of ambiguous stimuli allows to make a clear distinction between stimuli and perception. Perceptual multistability occurs when one stimulus leads to multiple different percepts in the same observer. This way, we can study how a percept emerges without the confounding factor of stimulus change. In this PhD thesis, we use ambiguous stimuli to study variability in multistable perception. In the first three empirical chapters, a 'local-global' ambiguous motion stimulus, which enables both a 'local' and 'global' apparent motion percept, is employed. In the last empirical chapter, a motion quartet stimulus, enabling apparent motion percepts in different directions, is employed. Although individual differences have often been considered in research, many inter-individual (between individuals) and intra-individual differences (within individuals) in the general population have been neglected when they are not the result of an a priori defined manipulation or demographic group. However, these individual differences and perceptual dynamics may be very informative and are therefore a major focus in this PhD thesis. Multistable perception is an excellent test case to study this variability in depth. A fundamental question pertains to what the influencing factors are that determine the variability in multistable perception. These factors are often described in terms of their "position" on the different levels of the visual system (i.e. low-level, mid-level, and high-level) and different empirical chapters in this PhD thesis examine the influence of different factors along these levels. The first empirical chapter of this thesis, 'CSF study', examines the relationship between the "low-level" measure of individual luminance contrast sensitivity and the perception of the 'local-global' ambiguous motion stimulus. The perception of the 'local-global' ambiguous motion stimulus is characterized by a 'shift to global' over time and the underlying factors remain unclear. Therefore, the second empirical chapter, 'Relevance study', examines the role of mere exposure vs. experienced "higher-level" relevance in an auxiliary task on the perception of this stimulus over time. In the third empirical chapter, 'EEG study', electrophysiological correlates of the perception of the ambiguous local-global motion stimulus are examined. We measure electro-encephalography (EEG) activity during perception of the ambiguous local-global motion stimulus vs. disambiguated versions of this stimulus over time. Moreover, we compare activity during perception of the 'local' and 'global' percept. The first empirical studies allowed us to control for variability caused by the stimulus. However, visual perception is the result of complex interactions between observer and stimulus characteristics. Therefore, in the last empirical chapter, 'MQ study', we explore the perception of multiple variations of a motion quartet stimulus and examine the interaction of these different stimulus characteristics with individual differences. Our understanding of visual perception is still growing and it is important to note that the terms low- and high-level may be used to imply different meanings. The discussion chapter, 'Level with me', addresses the ambiguity of the terms low- vs. high-level, and aims to illustrate where the distinction between different levels can be useful vs. where it can be contra-productive for developing a better understanding of visual perception.
Jaar van publicatie:2022
Toegankelijkheid:Open