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Michael N. Tombu, Adriane E. Seiffert; Exploring the effects of crowding in multiple object tracking using a dual-task paradigm. Journal of Vision 2006;6(6):770. doi: 10.1167/6.6.770.
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© ARVO (1962-2015); The Authors (2016-present)
A dual-task paradigm was employed investigating the attentional demands of crowding in multiple object tracking (MOT). Subjects tracked four of eight randomly moving dots. At some point a tone sounded, requiring a speeded response based on pitch. Previous research indicates that this tone task demands attentional resources. In Experiment 1, MOT difficulty was manipulated by having all dots either briefly attract one another, causing increased crowding, or continue to slightly repulse one another, causing no increase in crowding. We hypothesized that increasing crowding would make the tracking task more difficult and that it would demand increased attentional resources. If our crowding manipulation demands attentional resources in MOT, then the effect of crowding should be larger when it occurs temporally close to the tone (short SOA) as compared to when it occurs after tone processing is complete (long SOA). Results confirmed this hypothesis; increasing crowding had a significantly larger effect at the short SOA compared to the long SOA. Experiment 2 aimed to demonstrate a manipulation that would increase tracking difficulty while not increasing attentional demands. Dot contrast was briefly manipulated, either at a short or a long SOA relative to the tone. The effect of contrast was additive with SOA indicating that reducing contrast increases tracking difficulty, but does not increase attentional demands. These results indicate that increased crowding and reduced contrast both lead to worse MOT performance, however, only increasing crowding causes tracking to become more attentionally demanding.
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