Article Review: How Many Object Can You Track?: Evidence for a Resource Limited Attentive Tracking Mechanism
Before the paper by Alvarez & Franconeri (2007), the general consensus was that people are able to track about 4 moving objects at any given time. However to some, it was clear that this issue is more complicated than the original view; which is the most likely inspiration for this further research. In the paper by Alvarez & Franconeri (2007), it is found that it is not as simple as the previous approach; for example they looked at how speed affected the ability to track objects and found that speed did have an affect whereby the higher the speed; the participants ability to track all objects would decrease. Alvarez & Franconeri (2007) also found an effect where, if the objects were allowed to move closer together the participant would find it harder to track, but more so in the faster condition.
Alvarez & Franconeri (2007) did 2 experiments. The first looks at how increasing the speed in which the stimulus moves, affects how many stimuli that the eye can track. This is done by first presenting a number of identicle black circles on a white computer screen, identical distractor circles will then appear. The circles then start moving. It is the participant’s task to follow these circles and identify the target stimuli (not distractors) at the end of the task. It is found that the more stimuli presented on screen, the less chance there is of identifying the correct stimuli at the end. Alvarez & Franconeri (2007) point out that participant’s should be able to identify less stimulus as the speed increases. It is found that when 1 stimulus is presented, participants can track it a high speed. The speed in which the participant can identify the correct stimuli decreases with every stimulus added. There was also an accuracy check to made sure the each participant’s results was a true representation of what was being observed. The second part of the study examined an effect when the minimum amount of space in between each stimulus was manipulated. This was done in a similar way to part one of the study. However it was the minimum distance that was allowed in-between each stimulus that was manipulated and not the amount of stimuli on screen. Results show that minimum spacing, speed of stimulus and the interaction, all had significant results (all were p=<.001).
There is also similar evidence from Howard & Holcombe (2008) that shows an effect where the more objects a participant tries to attend to, the worse the tracking of the objects becomes. For the flexible resource model, the research cited is explained further. For example Green & Bavelier (2006) is used to show that people who play video-games will do better in the object tracking tasks due to practise of similar tasks. Alvarez & Franconeri (2007) also cite various articles into factors that could affect the object tracking; for example, age differences (Trick et al, 2003).
Franconeri et al (2008) argued in a study that only looked at the speed in which the participant could track objects on a small and large display; Franconeri et al (2008) found similar finding to the Alvarez & Franconeri (2007) study. However; Franconeri (2010) later advances on Experiment 2 and argues that object tracking performance is purely based on object spacing and no other factor would affect object tracking. It could be said that this is conflicting evidence and more research is needed in this area to fully understand the effect of speed and minimum spacing with regard to object tracking.
While Alvarez & Franconeri (2007) may have found these results in their study, it could be argued that the results are not fully valid and not be a true picture of perception in the real world. The most basic argument against the Alvarez & Franconeri (2007) view is that; in the real world, it is rare for someone to have to track moving black...
References: Alvarez, G. A. & Franconeri, S. L. (2007). How Many Objects Can you Track?: Evidence For a Resource-Limited Attentive Tracing Mechanism. Journal of Vision, 7(13), 1-10.
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Franconeri, S. L., Jonathan, S. V. & Scimeca, J. M. (2010). Tracking Multiple Objects Is Limited Only by Object Spacing, Not by Speed, Time, or Capacity. Psychological Science, 21(7), 920-925.
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Trick, L. M., Audet, D. & Dales, L. (2003) Age Differences in enumerating things that Move: Implications for the Development of Multiple-Object Tracking. Memory & Cognition, 31, 1229-1237.
Trick, L. M., Jaspers-Fayer, F. & Sethi, N. (2005). Multiple Object Tracking in Children: The ‘Catch the Spies’ task. Cognitive Development, 20, 373-387.
Xu, Y & Chun, M. (2009). Selecting and Perceiving Multiple Visual Objects. National Institute of Health, 13(4). 167-174.
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