Perception of Visual Illusions in Children and Teenagers With ADHD

Susceptibility to visual illusions is a consequence of the adaptation of the visual system, however, their perception or lack of it reflects differences in more general, global cognitive processes. Few studies have focussed on the susceptibility of individuals with attention-deficit/hyperactivity disorder (ADHD), even though visual impairment and percept differences have been thoroughly documented.

The present study evaluated 75 children (ages 6.09-12.99 years, 72% male) and 37 teenagers (ages 13-16.95 years, 62% male) with ADHD, and a sex-and-age matched sample of typically developing peers. They were tested with 103 pairs of illusory and control images spanning five illusion types.

We found increased susceptibility to the Müller-Lyer and Kanizsa Subjective Contour and decreased susceptibility to the Ebbinghaus illusion among children with ADHD when compared to typically developing controls. No differences were found for susceptibility to the Simultaneous Contrast and Moving Snake illusions. As for reaction times, we did not find differences between participants with ADHD and their control peers when judging illusions; however, in general participants give answers faster in the illusory trials than in control trials with the same magnitude of difficulties which also confirm the susceptibility of the illusions.

Our findings point to small but important perceptual alterations, such as slightly reduced or delayed top-down or global processing ability in children with ADHD. Further research can focus on how these alterations may be useful to detect developmental alterations and understand perceptual difficulties in children with neuropathology.