Thesis defense Ella Bosch (Donders Series 624)

30 October 2023

Promotors: Prof. dr. Floris de Lange and Prof. dr. Jan Buitelaar

The influence of the past in visual perception in autism

Autism is known for its behavioral and social characteristics, but atypical sensory experiences, such as sensitivities to light, can also be part of the picture. These sensory experiences might be explained by the way that information from the senses is processed by the brains of autistic people.

In the typical brain, sensory input from the eyes is combined with contextual information. One general type of context is the past. Using the past when processing information from the eyes is believed to lead to a better, more usable perceptual experience. Using the past less, then, would negatively impact our perceptual experience, making it more unstable and noisy and perhaps leading to the sensory experiences in autism.

In this dissertation, I asked the question: do autistic people use the past less than typical people when processing sensory input from the eyes? To try to find this out, we looked at three different ways that the past influences perception (adaptation, serial choice bias, and familiarity), and then compared autistic adolescents to typically developing adolescents to measure any differences.

First, in Chapter 2, we looked at what role the recent past plays in people’s decisions on visual information in a typical population. We found that the recent past biased perceptual decisions in two directions. Decisions were both biased away from the previous visual information (resembling adaptation) and biased towards the previous decisions (serial choice bias).

Then, in Chapter 3, we investigated these phenomena in autism. However, we did not find differences in adaptation or serial choice bias between autistic and non-autistic adolescents. Based on this, autistic people may use the recent past similarly to non-autistic people when processing visual information.

Next, in Chapter 4, we shifted our focus to the influence of the more distant past. We found that both people’s behavioural responses and the responses of their brain seems more efficient when seeing familiar images compared to novel ones. We repeated the experiment with autistic and non-autistic adolescents and did not find any differences between the groups. This suggests that the influence of prior exposure to visual information is similar between autistic and non-autistic people.

Finally, in Chapter 5, I summarized the findings from the previous chapters and concluded that we did not find any evidence for differences between autistic and non-autistic people in how the past influences the processing of visual information. I also discussed different possible interpretations of our findings.