Object individuation in enumeration and multiple-object tracking

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In a complex dynamic visual scene, there are often too many objects to be able to perceive them all at once. Consequently, selective attention is needed to choose some while others are ignored. To select an item among others, to touch it or look at it in detail, there needs to be a way to "individuate it" so that it can be considered as individual, separate from other items that look the same. As well, because items often move and change, there needs to be a way to track them, so that each item will be considered as the same "one" despite changes in properties and position. The objectives for this research are to study how tracking and individuation change across the lifespan, and how these abilities relate to working memory, attention, and auditory and tactile tasks that involve keeping track of location. To study these, I use two related tasks that both require item individuation. One is multiple object tracking: the ability to keep track of the positions of multiple target items as they move among other visual items, an important component of many daily tasks, including driving. A second task is spatial enumeration: the ability to say how many items there are in a visual scene. These investigations will have an impact on theories of life-span development, attention, numerical cognition, and perceptual-motor coordination. Furthermore, in order to understand age-related disorders such as Alzheimer's disease it is essential to have information about how performance changes with normal aging. There are other practical implications as well. In Canada, vehicle collisions are a leading cause of injury and death, but they also exact costs to society in terms of lost work, social and health care expenses, and damages. Transport Canada estimates that every year these costs sum to 4.9% of Canada's annual Gross Domestic Product. Older drivers are especially at risk for certain types of collision and are most likely to die or sustain serious injury as a result. By studying individuation and tracking, it may be possible to develop predictors to identify drivers who pose risks to themselves and others, thus permitting interventions to reduce collisions and deaths.