Children Are Fundamentally Different in Visual Perceptual Learning

Post by D. Chloe Chung

What's the science?

Visual perceptual learning is the phenomenon in which our visual performance improves as we continue to practice perceptual tasks composed of visual cues. Visual perceptual learning can also be influenced by our age. It has been previously reported, for example, that older individuals perform drastically different in visual learning compared to younger adults. However, it has been unexplored whether visual perceptual learning also changes during development, such as from childhood to adulthood. This week in Current Biology, Frank and colleagues show that visual perceptual learning is different in children and young adults as they do not handle visual information in the same way.

How did they do it?

On the first day of the study, 20 healthy children (7-10 years old) and 20 healthy young adults (18-31 years old) fixated their gaze to the center of the screen and monitored 70 dots of which some of them were moving in the same direction. At the end of each of 300 trials, the participants were asked if they noticed the motion of dots to be coherent or random. Their “detection threshold” was determined based on the minimum percentage of dots moving in the same direction required for the participants to perceive the coherent motion. The next day, during the “pretest” session, the participants again monitored moving dots and determined the direction of the dots’ motion, similar to the first day of the study. On the third day of the study, participants had the first of several “exposure sessions” where they were exposed to moving dots either at threshold or at suprathreshold levels for coherent motion detection while completing a visual task at screen center. Specifically, on each trial, participants were presented with a stream of eight images, either “target” (two different animals) or “distractor” (six non-animal objects), surrounded by dots moving in a certain direction. At the end of each of 110 trials, participants were shown with four animal photos and asked to answer which two animals (targets) were presented in what order on this trial. A total of 12 exposure sessions was conducted on separate days. On the last day of the study, the participants underwent the “post-test” session where they repeated the same task from the “pre-test” session” to see if their visual performance for motion direction discrimination improved after the exposure sessions. Additionally, the participants took another test that measures their selective attention, in which they had to determine peripheral stimuli among distractors while focusing on the main target at the center of the visual field.

What did they find?

First, the authors found that children and young adults had a comparable detection threshold, meaning that the participants were similar in their baseline ability to detect the coherent motion of dots regardless of their age. Next, the authors evaluated whether the participants improved in distinguishing the motion of moving dots after being repeatedly exposed to moving dots while completing a central visual task. Between the pre-test and post-test, both children and young adults showed approximately 40% performance improvement in their performance when the moving dots were presented at the threshold level. Interestingly, when moving dots were presented at the suprathreshold level, children still showed improved visual performance while adults drastically decreased in their performance, indicating that visual perceptual learning substantially differs between two age groups. This noticeable change in performance only occurred for motions that were linked to targets that the participants had to focus on during the exposure session.

To rule out the possibility that children’s improvement in visual performance was due to their inability to ignore visual features that were irrelevant to tasks during their visual exercise, the authors analyzed the correlation between selective attention ability and visual performance change for motion discrimination after suprathreshold exposure across participants. This analysis showed that children with greater selective attention ability also showed greater performance increases. Importantly, this correlation between selective attention ability and visual performance change was not found among young adults, emphasizing that mechanisms of visual perceptual learning are fundamentally different between children and young adults.

What’s the impact?

This study is the first one to report that visual perceptual learning remains dynamic as we advance from childhood to adulthood, due to differences in the way children handle visual cues compared to young adults. Findings from this study provide another important piece of evidence that similar to many of our other learning abilities, visual perceptual learning can dramatically change throughout our lifetime. For future studies, it will be interesting to investigate specific brain regions or neurotransmitters that are involved in the mechanistic differences between children and adults in their visual perceptual learning.

Frank et al. Fundamental Differences in Visual Perceptual Learning between Children and Adults. Current Biology (2020). Access the original scientific publication here.