A psychophysical investigation and a philosophical discussion on perception

2017
Author: 
Doğa Gülhan

Time seems to be a central mediator of many phenomenal experiences. The current thesis was an attempt to integrate a body of empirical work into philosophical discussions. Firstly, visual mechanisms of time perception were investigated, focusing on the dichotomy of time and motion using psychophysical methods. Specifically, short-term adaptation-based apparent duration compression was examined experimentally: after introducing a brief visual stimulus, perceived duration of the upcoming stimulus at the same side was compressed in comparison to the following stimulus presented at the opposite side. The main results indicated that a dynamic short-term adaptor induces a significant subjective duration compression (~10%) on a subsequently presented test stimulus only for global motion at 50% coherence but not for those at 0%. These results pointed out that the effect may be tuned to sensory motion signals processed by the higher-level global motion areas such as middle temporal complex. Controls provided evidence that this subjective time compression was dissociated from adaptation-induced changes in perceived speed. The duration compression was present even under interocular conditions: this interocular-transfer seems to further supported the idea that high-level motion processing areas might be involved in processing event-time, following an earlier locus at the lateral geniculate nucleus (e.g. Johnston et al, 2006; Ayhan et al, 2011). Secondly, ontological and epistemological issues regarding (perceptual) time was discussed. This part sought to outline some philosophical debates in the context of empirical findings where possible. Without being a radical advocate of a particular philosophical view, a speculative area of discourse was illustrated.