Introduction
The following demo is based on findings reported in Davidenko et al. (2017). They describe a case in which the first author of the paper perceived apparent congruent motion in random noise during an fMRI study, most often following a rebounding pattern (up-down-up-down). They dubbed this phenomenon Illusory Apparent Motion (IAM).
Davidenko et al. (2015) show that presenting a moving pattern for 8 frames at a 2.5Hz frequency is enough to create IAM in 100% random noise for 2.4 seconds on average (6 frames), with 24% of participants showing little persistence (perceived IAM in 3 or fewer frames), and 28% showing higher persistence (IAM perceived for more than 7 frames).
This demo replicates supplementary video 1 from Davidenko et al. (2017), which replicates the findings of Davidenko et al. (2015). We use a grating stimulus with a rebounding motion (phase change of 0.2 or 0.8) at two frequencies (2.5Hz and 1Hz) to measure sensitivity to IAM as a function of motion amplitude and frequency.
Prerequisites
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LabMaestro is installed and activated
Project Files
Timeline Overview
This experiment contains a single Timeline with 20 Epochs, each corresponding to a frame of motion. The first 5 epochs (Frame1-Frame5) show a Grating stimulus overlaid with random uniform noise. The grating gradually disappears (its amplitude is reduced by 0.2 on every frame after the first) until it becomes completely invisible starting on frame 6. From then on, only random noise is visible. Listen for Inputs objects (stop1-stop15) are included to measure the moment at which participants press the Space key, indicating they no longer perceive coherent motion in the noise. This sequence, by default, repeats 4 times in a 2x2 crossed design (2 frequencies X 2 phase changes).
Data Overview
Following a session of the experiment, you can export the collected data by right-clicking Recordings -> Export all recordings. By opening the resulting TSV/CSV file, you can see how long it took for the participant to press SPACE on each iteration of the timeline. As such, you can compare the time it took for the IAM perception to fade across all conditions.