Tag: Paul Dassonville

Dissociating the Time Courses of Two Neural Mechanisms Underlying the Rod-and-Frame Illusion

Presenter: Ernestine Brannon − Psychology

Faculty Mentor(s): Paul Dassonville, Jeffrey Peterson

(In-Person) Oral Panel—Neuron & Cognition

Witkin and Asch (1948) developed the rod-and-frame illusion (RFI) to investigate how the visual system uses context to determine an object’s orientation by providing a distorted visual field and examining its effects on orientation judgments. The RFI is thought to be driven by a combination of local and global mechanisms. The local mechanism is brought about by low-level visual properties causing an orientation contrast effect between the rod and edges of the frame. The global mechanism is the product of a compromise between the visual and vestibular systems. In this study, we examine the time courses associated with the local and global mechanisms thought to underlie the RFI. We also examined the effect on illusion magnitude when we isolated the global mechanism.Participants performed a two-alternative forced choice task where they made orientation judgments (clockwise or counterclockwise of vertical) of the RFI stimulus and a new type of stimulus, the knob-and-frame illusion (KFI), designed to isolate the global effect. We varied stimulus onset asynchronies to determine when the frame begins to bias perception of vertical and when the illusion reaches its full magnitude for each stimulus type. As predicted, we found the RFI had a greater illusion magnitude than the KFI. We found that the KFI and RFI unfolded under similar time courses. The influence of the frame began with negative SOAs and built until reaching a plateau early in the positive SOAs.

Autistic Tendencies and Visual Processing: A Local Bias versus a Global Deficit

Presenter: Melissa Dollar

Mentor: Paul Dassonville

PM Poster Presentation

Poster 10

Past research suggests that individuals with autism spectrum disorders (ASD) exhibit an enhanced locally-oriented processing bias, but have an attenuated tendency to use global contextual cues. In addition, the autistic trait of systemizing has recently been found to predict sensitivity to global contextual cues, where high systemizing tendencies are associated with a decreased tendency to pro- cess misleading global context (e.g., visual illusions.) It is currently unclear, however, whether individuals with heightened systemizing drives, such as those with autism, display the same decreased tendency to process context when it provides information beneficial to performance. The current study examined the extent to which systemizing tendencies were predictive of whether individuals could use beneficial global-contextual information in two perceptual tasks. For two different visual tasks we found a significant benefit of the presence of an upright frame (compared to no frame), and no correlation with the autism and systemizing quotients and the extent to which participants benefited from the global context of the frame. These results suggest that individuals with heightened systemizing drives, such as those with autism, can still utilize global information when it is beneficial to performance.