The Distribution of Attention Within Moving Objects

1
The Distribution of Attention Within Moving
Objects is Affected by Spatial
Probabilities Cary S. Feria and Maureen
Doyle Morehead State University

• Introduction
• Previous research has found that
• When several moving objects are tracked,
  attention is concentrated at the center of each
  object (Alvarez Scholl, 2005).
• The visual system attentionally prioritizes
  spatial locations based on the probabilities of
  stimuli appearing at each location (e.g., Geng
  Behrmann, 2005).
• Purpose
• How is the distribution of attention over
  multiple moving objects affected by spatial
  probabilities?

• Conclusions
• 1. These data suggest that two factors influence
  the distribution of attention to moving objects
• (a) attention has an inherent bias toward the
  centers of objects (consistent with Alvarez
  Scholl, 2005)
• (b) the attentional distribution is prioritized
  by spatial probabilities
• 2. When stimulus location is known with 100
  certainty, the center bias is eliminated.
• 3. Attentional prioritizations (based on stimulus
  probabilities) can move along with a continuously
  moving object.
• 4. These results are consistent with attentional
  prioritization theories of object-based attention
  (e.g., Shomstein Yantis, 2004).

Experiment 1

• Question
• When tracking moving objects, is attention
• (a) concentrated at the centers of the objects,
  or
• (b) prioritized by the spatial probabilities of
  stimuli?
• Probe probabilities
• Center high-probability condition
• center .8
• different-color end .1
• same-color end .1
• Different-color-end high-probability condition
• center .1
• different-color end .8
• same-color end .1
• probe probability conditions were run
  within-subjects in separate blocks

• General Method
• Multiple object tracking (MOT) task
• Observers tracked two target lines among two
  distractors
• Lines moved about the screen randomly for 20 s
  and grew and shrank
• Small circular probes appeared intermittently for
  215 ms on each target lines (a) center, (b)
  different-color end, and (c) same-color end
• Probability of probes occurring on each location
  was manipulated in each experiment
• Observers were informed of probabilities
• Observers pressed a key when they detected a
  probe
• Observers completed two blocks of 25 trials

high probability center
high probability different-color end
probe location
probe location

• Answer to question
• Both!
• Detection was enhanced at higher probability
  locations
• But overall, detection was better at the centers
  than the ends

References Alvarez, G. A., Scholl, B. J.
(2005). How does attention select and track
spatially extended objects? New effects of
attentional concentration and amplification.
Journal of Experimental Psychology General,
134(4), 461-476. Geng, J. J., Behrmann, M.
(2005). Spatial probability as an attentional cue
in visual search. Perception Psychophysics, 67,
1252-1268. Shomstein, S., Yantis, S. (2004).
Configural and contextual prioritization in
object-based attention. Psychonomic Bulletin
Review, 11, 247-253.

4.38.4
8.411.5
11.5

4.38.4
8.411.5
11.5
center probe (scenes not drawn to scale)
Experiment 2

• Question
• If probe locations are known with 100 certainty,
  will attention still be biased toward the centers
  of objects?
• probe probabilities
• center certain condition
• center 1.0
• different-color-end certain condition
• different-color end 1.0
• probe probability conditions were run
  within-subjects in separate blocks

• Acknowledgments
• We thank Allison Adams, Amy Baker, Jamie Cole,
  Josh Edwards, Philip Oliver, Nick Rudd, and Amy
  Vaughn for assistance with data collection and
  helpful conversations. We also thank Gilbert
  Remillard for valuable advice and discussions.
• Supported by KY NSF EPSCoR Grant 11-223162.

different-color end probe

• Answer to question
• No
• Detection was essentially equal on centers and
  ends (F1,7 .011, p .05)