Laterality in temporal processing and spatial attention

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Part 1: Investigators have recently been noting very `low-level' perceptual asymmetries. For example, normal participants exhibit reliable left hemisphere advantages for temporal processing tasks in the visual, auditory, and tactile modalities. There is increasing speculation that these temporal processing asymmetries underlie hemispheric specialization for higher functions such as language processing. The studies that are being proposed will evaluate these claims in both neurologically normal and clinical participant groups using tests of lateralized temporal processing. The tests will be grouped into two main categories. In the first category, participants will complete tasks that require the perception of rapid or rapidly changing events, such tests of two-flash fusion, gap detection, inspection time, and formant-transitions. The second main category of tests will involve the discrimination of temporal intervals, requiring explicit judgments of the length of two time intervals. In addition to providing insights into potential causes and nature of hemispheric specialisation, the research proposed could also inform clinical treatment of people with language disorders.Part 2: Neurologically normal people exhibit very strong and reliable lateral biases in spatial attention. Most people pay more attention to the left side of the object. Similarly, when asked to make judgements of size, numerosity, brightness, colour, or distance, normals usually exhibit leftward biases. 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. It looks like these leftward biases effect people outside of the laboratory too. In the real-world, 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 in the current proposal is an attempt to determine the conditions under which these biases exist and whether they influence other real-world activities, such as driving.