Increased use of priors in the oblique effect in children

Background: According to Bayesian inference models of vision, perception is affected by incoming input (i.e., likelihood) and by past experiences (i.e., priors). Although perceptual inference has been widely studied in adults, much less is known about how Bayesian inference is modified during development. Here, we study how priors impact perception during development by examining the oblique effect in children. In the oblique effect, adults exhibit lower motion direction thresholds and larger estimation biases for cardinals versus oblique motion directions. Methods: We compared the perception of motion directions using RDK motion stimuli in adults (ages 20-38) and children (ages 7-9). First, we determined individual coherence discrimination thresholds for near oblique and for near horizontal directions using a staircase procedure. Then, participants were presented their at-threshold motion directions (near horizontal/oblique) and moved a mouse to estimate directions. Results: Results indicated that children exhibited higher overall thresholds compared to adults. Both groups showed significantly lower thresholds for horizontal motion compared to oblique motion, with this difference significantly more pronounced in children. Additionally, both groups displayed significantly larger estimation biases for near horizontal directions, which again was significantly more prominent in children. Conclusions: Even though horizontal and oblique stimuli were presented at their corresponding thresholds, there were larger estimation biases for horizontal versus oblique in both groups. This suggests that these biases persist even when equating for difficulty, an important factor to consider in future computational models of bias and discriminability. Importantly, our results reveal that children exhibit larger oblique effects than adults. The overall worse thresholds in children (i.e, likelihood) may drive children to rely more on perceptual priors than adults, impacting their perception of motion. Our study contributes valuable insights into the developmental aspects of perceptual inference and the role of priors in perception during development.