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Farahnaz Ahmed, Alex Hwang, Erin Walsh, Marc Pomplun; Conspicuity of Object Features Determines Local versus Global Mental Rotation Strategies. Journal of Vision 2010;10(7):1005. doi: https://doi.org/10.1167/10.7.1005.
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© ARVO (1962-2015); The Authors (2016-present)
Most studies describe mental rotation as a top down process where the time to discriminate between identical or mirrored objects increases linearly with the angular deviation between them. Although mental rotation is regarded as a distributed processing task, its dependence on object features is still not well understood. Therefore, we investigated the effect of structured color cues on an object's surface with a mental rotation task. Observers viewed two side-by-side images of Shepard Metzler type objects rendered for the following conditions: (1) objects had distinctively colored surfaces (these surfaces had the same color from different viewpoints), (2) objects had distinctive yet differently colored surfaces (colors of the surfaces changed with every viewpoint), (3) objects had distinctive dark gray surfaces (similar to 1 with gray instead of colored surfaces), (4) objects without any color information (uniformly gray). The viewing angle differed between the two objects from an egocentric frame of reference and the task was to determine as quickly as possible if the objects were identical or mirrored. Reaction times and eye movement data were recorded. Rotation effects were seen across all four conditions, but they were largest for condition 2 and the smallest for condition 3. The color cues in condition 2 seemed to make the task less efficient as evidenced by the increased reaction times, number of fixations and number of comparisons made between the images compared to the other conditions. For larger angular deviation in condition 1, the highly distinctive cues seemed to bias the observers' strategy toward comparing the local object structure near the cues, as indicated by more comparisons in further spread-out locations. The results suggest that, particularly for highly demanding rotation tasks, distinctive features induce multiple local comparisons of the object structure whereas the absence of such features tends to induce mental rotation of larger parts of the object or the entire object.
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