The Laterality of Everday Life

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Our everyday behaviours are profoundly influenced by functional and anatomical brain lateralization. Motor biases such as handedness have been studied in great detail, but our spatial biases are much less well understood. The program of research described in this proposal will survey the extent and potential causes of these biases, often examining human behavior in a naturalistic context, outside of the laboratory. This proposal details three (sometimes overlapping) streams of research: (A) Lateralized Spatial Attention, (B) Biases in Perception of Light Source, & (C) Spatial Biases while Driving.***(A) People exhibit very strong and reliable leftward lateral biases in spatial attention. The cause of these biases is unknown. It could be because people tend to scan objects from the left to the right (like reading English), or because people pay more attention to the left side of space. Outside of the laboratory, when people collide with stationary objects while walking, they tend to do so with the right side of their body. This suggests that individuals underestimate the proximity of objects to the right. The research proposed is an attempt to determine the conditions under which these biases exist.  *** (B) People tend to preferentially construct and display images that are lit from the left. This effect is readily observable in an art gallery, where 66%-75% of the images will show a lighting bias towards the left. This effect is also observable in magazine advertisements, amateur photographs, and laboratory tasks under carefully controlled conditions. It is currently unknown why people prefer this lighting arrangement, but it could be related to the right hemisphere's dominance for spatial attention. Alternately, these biases could be caused by native reading direction, and I will test this by including people whose first language reads from right to left (eg. Urdu, Farsi). ***(C) I am currently coordinating data collection for the Canadian Naturalistic Driving Study, a 2-year study of 125 drivers. We have installed a Data Acquisition System (DAS) that provides continuous multi-camera video recording, radar, and GPS data during real-world driving behavior. I am proposing that some of this data be coded and analyzed for lateral biases in judgments of proximity of other vehicles and stationary objects, and whether these biases interact with other factors (such as conversation with passengers, cell-phone calls, texting). Specifically, I am predicting that drivers will exhibit leftward biases for distance judgments, overestimating the proximity of leftward objects and vehicles, leading to a greater chance of right-side collisions. I also predict that braking latencies for leftward-approaching hazards (such as pedestrians, cyclists) will be shorter than comparable events from rightward hazards. **