Finding a way to diagnose autism early in development is crucial for devising new interventions and understanding its underlying neurobiological causes. It is, however, difficult to detect characteristic deviations in behavior or brain function in infants and toddlers. Measuring pupil size may be the right tool. The test is noninvasive, quick and easy to use, even in newborn infants. It is also surprisingly revealing of complex brain processes.

The simplest form of pupil response is to changes in light level. A delay in the light response can reveal processing delays in other parts of the brain. Previous research has shown that individuals with autism have a delayed pupil response to light. To increase the potential practical application of pupil measurements, Scott Murray and his colleagues at the University of Washington seek to replicate and extend previous findings by using simple, off-the-shelf equipment: a readily available eye tracker and a standard computer monitor. In addition, the researchers propose to significantly extend the age range under study by including children with autism as young as 3 years old. Their goal is to develop an early diagnostic tool that can be reliably used in a variety of clinical and non-clinical settings.

Besides responding to light, the pupil is also modulated by more complex visual information. For example, it constricts when looking at a photograph of the sun. This implies that pupillary behavior reflects the integration of contextual information (here, environmental conditions that are normally associated with high light levels). Murray and his group propose to measure pupillary responses to complex images in a group of young children. They aim to provide an objective and early index of contextual processing — a perceptual ability that is likely to be impaired in autism.