Figure 1. Methods and stimuli used in these experiments. a, Motion stimuli were 100 Gaussian profile luminance blobs at maximum contrast, with 50 having positive and 50 having negative contrast. b, Blobs translated rigidly for 200 ms in a direction that was jittered around a cardinal direction. Cardinal directions were blocked and presented in random order and jitter around the cardinal was randomly sampled from a set of directions: ±1.5°, ±3°, ±6°, ±12°, ±24°, and ±48° (Experiments 2, 3, and 4), or 0°, ±1.5°, ±3°, ±6°, ±12°, and ±24° (Experiment 1). c, Due to temporal integration, fast-moving random-dot patterns leave oriented trails that can be encoded by orientation-selective mechanisms. In this example, a translating random-dot pattern has been linearly integrated over 100 ms. The summed motion frames take on a streaky appearance with a clear but slightly noisy orientation along the motion trajectory. d, Intertrial data analysis. On each trial, participants judged if the direction was clockwise or anticlockwise of the cardinal direction. For every trial in the sequence, the response to a given trial n was binned into a category determined by the direction presented in the preceding trial n − 1.