Authors
Catherine Manning; Louise Neil; Themelis Karaminis; Elizabeth Pellicano

The effects of grouping on speed discrimination thresholds in adults, typically developing children, and children with autism

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Abstract/Introduction

Adult observers show elevated speed discrimination thresholds when comparing the speeds of objects moving across a boundary compared to those moving parallel to a boundary (Verghese & McKee, 2006)—an effect that has been attributed to grouping processes in conjunction with a prior for smooth motion. Here, we extended Verghese and McKee's (2006) paradigm to typically developing children (n = 35) and children with autism (n = 26) and compared their performance with that of typical adults (n = 19). Speed discrimination thresholds were measured in three conditions: (a) with dots moving parallel to a boundary, (b) with dots moving perpendicular to a boundary, and (c) with dots in each stimulus half moving in orthogonal, oblique directions. As expected, participants had higher speed discrimination thresholds when dots appeared to cross a boundary compared to when dots moved parallel to the boundary. However, participants had even higher thresholds when dots moved in oblique, orthogonal directions, where grouping should be minimal. All groups of participants showed a similar pattern of performance across conditions although children had higher thresholds than adult participants overall. We consider various explanations for the pattern of performance obtained, including enhanced sensitivity for shearing motions and reduced sensitivity for discriminating different directions. Our results demonstrate that the speed discrimination judgments of typically developing children and children with autism are similarly affected by spatial configuration as those of typical adults and provide further evidence that speed discrimination is unimpaired in children with autism.


Conclusion/Results

Spatial arrangement clearly affects speed discrimination sensitivity in adults, typically developing children, and children with autism. However, our results question whether the best explanation for these effects is grouping. Instead, it could be that observers use shearing cues to improve speed discrimination and that speed discrimination is hindered when comparing across different directions. To hone in on the precise mechanisms, future research could benefit from repeating some of Verghese and McKee's (2006) other conditions in a large group of adult observers.


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Testimonials


My eight year old daughter was terrified to go to the eye doctor for fear of her eyes being dilated. The doctor was SO KID friendly! He immediately made her comfortable by engaging her in conversation. It was a geat experience.


Joya B.

Dr. Garbus spent an amazing amount of time to solve my very complicated visual problems. Over the years he has continually achieved results beyond what others felt possible. He is always up to date on the latest science. He is great!


Dolores K.

Family Vision Care Valencia makes it so easy. Staff is knows what they are doing and Dr. Garbus is thorough and kept me well informed during the exam.


Kristy B.

I have been coming to Family Vision Center for almost 20 years. Dr. Garbus has been able to help my vision when other doctors could not. Now my kids see him as well. I highly recommend this office!


Autumn C.

The Doctor is very good. I felt on this visit he seemed rushed. I had questions to ask him but he was already with another patient. I still do not know if my eyes are the same , worse, or better.


Howard B.

All the staff is friendly, helpful and knowledgeable, and has been for all the years I have been going there.


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