Abstract
Adapting to high temporal frequency oscillating gratings or flickering Gaussians reduces the apparent duration of a subsequently presented sub-second dynamic stimulus (Johnston, Arnold, & Nishida, 2006, Current Biology, 16(5):472–9). Here, we measured adaptation-induced temporal distortion using counterphase-modulated gratings and then investigated whether the perceived duration of a counterphase flickering central grating is influenced by a simultaneously presented surround, which would indicate contextual effects in duration perception. In the first experiment, the standard (10 Hz, 600 ms, 1 c/deg) was presented at the adapted location while the comparison (100–1100 ms) was always displayed on the unadapted side. The apparent temporal frequencies of the two tests were matched using individual measurements of the temporal frequency shifts that could be observed following adaptation. Adaptation to 20 Hz induced duration compression with adaptation to 5 Hz inducing weaker duration compression. Overall duration compression was weaker for counterphase-modulated adaptors as compared to drifting or Gaussian flickering adaptors. In the second experiment, a standard disc (10 Hz, 600 ms) was surrounded by a 5 or 20 Hz counterphase-modulated annulus (2 sec) in two different blocked conditions. The comparison stimulus (100–1100 ms, 10 Hz) was always surrounded by a 1 Hz counterphase-modulated annulus (2 sec). The onset and offset of the tests relative to those of the surrounds were randomised across trials. Using a similar procedure to Experiment 1, the apparent temporal frequency of the standard was matched to that of the comparison. The task was to compare the duration of two sequentially displayed tests both temporally embedded in and surrounded by a dynamic surround. We found that while a 20 Hz context induced a ~12% statistically significant expansion (p = 0.012) of the perceived duration of the central pattern, no statistically significant difference was observed when the surrounding context was 5 Hz. The modulation of the duration of the inner disc by non-overlapping surround provides evidence for long-range spatial interactions in duration perception.
The Leverhulme Trust & NTT Communication Science Laboratories.