Decoding the processes behind perceived bistable structure-from-motion

What is it about?

Imagine looking at a screen filled with seemingly randomly displayed dots. Immediately when the dots start to move relatively each other, you perceive an emerging 3D shape. This intriguing phenomenon is known as "structure-from-motion" (SFM), where the coordinated motion of dots on a 2D plane tricks our brain into seeing a three-dimensional object. When we observe these moving dots, our perception of the 3D shapes can become unstable, with depth relations that seem to flip back and forth. This study investigates the processes behind these perceptual reversals, focusing on two types of SFM stimuli: spinning and wobbling shapes. This was done by measuring how long participants maintained a stable perception of these 3D shapes before experiencing a reversal. The durations of stable perceptions of the bistable SFM-stimuli, static and wobbling versions of the famous Necker cube, an optical illusion that also flips back and forth in perception were compared. Interestingly, the results showed that the wobbling SFM shapes resulted in stable perceptions that were much longer than for any other stimuli. The duration of the stable perceptions of the wobbling SFM was not correlated with those of the spinning SFM shapes or the Necker cubes. However, correlations were found among the other stimuli, suggesting different underlying processes at play for the wobbling SFM shapes (see figure below). For the spinning SFM shapes, perceptual reversals are known to be driven by a bottom-up process, involving adaptation and recovery cycles between neural populations. This study suggests that the wobbling SFM shapes disrupt this bottom-up process and instead engage top-down processes, which are influenced by our brain's higher-level cognitive functions. Another finding was the impact of learning. The study was divided into two sets of viewing periods, and biases observed in the first set disappeared in the second set, indicating that participants' perceptions were influenced by their initial viewing experience. Moreover, the study explored the role of visual imagery vividness—a measure of our brain's intrinsic top-down processes. However, no correlation between participants' visual imagery scores and their rates of perceptual reversals were found. In summary, this research sheds light on the intricate relation between bottom-up and top-down processes in our brain when interpreting ambiguous visual stimuli. By understanding these mechanisms, we can better grasp how our brains construct a coherent picture of the world from sparse motion information. This insight not only enriches our knowledge of visual perception but also has potential applications in other areas of psychology such as relating reversal rates while viewing bistable images with clinical diagnoses or personality traits.

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Photo by Ion Fet on Unsplash

Photo by Ion Fet on Unsplash