Page 71 - It' about time: Studying the Encoding of Duration
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                                Chapter 4  Toolbox (Brainard, 1997; Pelli, 1997). Participants viewed the stimuli with their head resting in a chinrest placed 57 cm from the screen. The auditory stimuli were presented using a Sennheiser HD201 on-ear headset. All stimulus timings were verified using a dual-channel oscilloscope. All stimuli consisted of a circular radial grating (diameter of 2.0°) with a sinusoidal luminance modulation (100% Michelson contrast) of 4 cycles. On each presentation, this stimulus was either static or rotating at 2.08 cycles/ second. This resulted in each individual point of the stimulus being modulated sinusoidally at 8.33 Hz. All stimuli were presented on a gray background (32.5 cd/m2) and accompanied by a central fixation cross (64.3 cd/m2). Each radial grating was presented peripherally at a distance of 4° degrees from the central fixation cross. In all tasks, test and reference stimuli were presented at one of four possible positions, the location of which was counterbalanced across participants (0, 90, 180, or 270° angle from fixation). All adaptation stimuli were presented randomly across 10 possible locations at a 45 to 315° angle from the test stimulus with an inter stimulus interval (ISI) ranging between 500 -750 ms. This spatial configuration was used to reduce the overall adaptation to the non-temporal stimulus features and the temporal frequency of our adaptation stimuli. In addition, this configuration resulted in a minimum separation of 3.06° of visual angle between the adaptation and test stimuli. At this distance any adaptation to the non-temporal features or temporal frequency of the adaptation stimuli should not affect our measurement of perceived duration at the test location (Johnston et al., 2006; Zhou et al., 2014), while still allowing for effective measurement of the DAE (Maarseveen et al., 2017). Auditory reference stimuli consisted of a burst of white noise (60dB) with a 10 ms linear onset and offset ramp. Procedure TFITD illusion magnitude estimation. Since each participant differs in the magnitude of his or her TFITD illusion, the duration of the perceptually matched stimuli and the central reference stimulus needs to be tailored to each individual participant. We estimated the magnitude of the TFITD illusion for individual participants by having them completed a visual duration judgment task. In this task, participants compared the duration of a reference grating that lasted 300 ms. to a static test grating with a variable duration. Depending on the condition, the reference grating was either static or rotating. The order in which the reference and test were presented was randomized and counterbalanced 70 


































































































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