Page 87 - It' about time: Studying the Encoding of Duration

Chapter 5 temporal frequency during occlusion should only be observed for occluded stimuli and not for stimuli with fading luminance-modulation. To summarize, if temporal frequency is represented during occlusion we should observe time dilation both when the stimulus remains visible as well as when it becomes occluded. Additionally, time dilation for the occluded stimuli should be larger than any time dilation observed in the extinction condition. Material and Methods Participants. A total of 20 healthy adults participated in this study (7 male; mean age=22.5, SD=3.41). All participants had normal or corrected-to-normal vision and normal stereoscopic vision. They received monetary reward or course credits as compensation for their participation and were naïve as to the purpose of the experiment. The experiment was conducted in line with the principles expressed in the Declaration of Helsinki and received approval by the local ethics committee. All participants were informed that they could stop their participation at any time and that the data would be processed anonymously. After agreeing with these terms all participants signed a written informed consent form. Apparatus and stimuli. Stimuli were presented on two linearized 24-inch LCD monitors (screen resolution at 1920 x 1080 pixels, 60 Hz refresh rate) controlled by single Windows workstation (Windows 10) running MATLAB 2010A (MathWorks, Inc.) and the Psychophysics Toolbox (Brainard, 1997; Pelli, 1997). Both screens were viewed dichoptically through a mirror setup. Throughout the experiment images from the right screen were projected to the right eye and images from the left screen to the left eye. The total distance between the participant and each of the screens was ~85 cm. From this distance the full screen subtended 35.38° x 20.08° of visual angle. Head movements were restrained using a chinrest. All stimuli were presented on both monitors and were presented on a grey background (62.5 cd/m2). To facilitate binocular fusion between the two images all presentation was accompanied by a square, pink-noise frame (96.79% Michelson contrast) that started 11.2° x 11.4° from the center of the screen and subtended 2.8° x 2.8° of visual angle. 86