Here
is a
list of our ongoing projects! To learn more about each one, simply
click on a link to expand the project description.
PAC@VSS
We enjoy presenting our research and getting feedback at
the annual Vision Sciences
Society conferences. Now you, too, can enjoy our abstracts and posters
from the comfort of your desk!
PAC@VSS: 2012 | 2011 | 2010 | 2009
Current Projects
How does self-movement affect multiple object
tracking?
Investigations of multiple object
tracking aim to further our
understanding of how people perform common activities such as driving
in traffic. However, tracking tasks in the laboratory have overlooked a
crucial component of much real-world object tracking: self-motion. We
investigated the hypothesis that keeping track of one's own movement
impairs the ability to keep track of other moving objects. Participants
attempted to track multiple targets while either moving around the
tracking area or remaining in a fixed location. Participants' tracking
performance was impaired when they moved to a new location during
tracking, even when they were passively moved and when they did not see
a shift in viewpoint. Self-motion impaired multiple object tracking in
both an immersive virtual environment and a real-world analog, but did
not interfere with a difficult non-spatial tracking task. These results
suggest that people use a common mechanism to track changes both to the
location of moving objects around them and to keep track of their own
location.
Related
Publications: Thomas, L. E., & Seiffert, A. E. (2011). How
many objects are you worth? Quantification of the
self-motion load on multiple object tracking. Frontiers in
Psychology. [ link ]
Thomas, L. & Seiffert, A. E. (2010). Self-motion impairs multiple
object tracking. Cognition. [ link
]
How do
people decide what information is salient?
DSR
#22703 STTR Research Project: This collaboration between Vanderbilt
University computer scientists and cognitive scientists will work with
DiscernTek analysts to create a a system of human-computer interfaces
for application to military command or business that represents human
perception and cognition for the purpose of providing ready access to
salient information.
Where do people look during multiple
object
tracking, and why?
Multiple object tracking measures the ability to covertly attend to
multiple locations over time. Previously we demonstrated that
participants tracking multiple targets often look at the center of the
target group (Fehd & Seiffert, 2008), a strategy we label "center-looking".
This is intriguing because participants are not always looking directly
at targets or saccading between them, a strategy we label "target-looking".
The current experiments investigated whether people engage in
center-looking only when target-looking is too difficult.
Participants tracked targets moving randomly amidst distractors while
we measured the amount of time they viewed the targets or the center of
the targets. To increase the demand for foveation and hence increase
target-looking, a series of 3 experiments manipulated dot size (from
0.3 to 0.06 degrees visual angle), dot speeds (from 2 to 24 degrees per
second), and target motion (similar or dissimilar). These experiments
tested a range of difficulties, pushing participants to their
perceptual limits. Results show that center-looking persists
regardless of the ease with which targets can be foveated.
Center-looking is not the default alternative to target-looking, but
instead may reflect a different cognitive process. It seems that the
time spent looking away from targets is not determined by the
difficulty of looking at them

Related Publications: Fehd, H. M. &
Seiffert, A. E. (2010). Looking at the center of the targets helps
multiple object tracking. Journal of Vision, 10(4). [ link ]
Fehd, H. M. & Seiffert, A. E. (2008). Eye movements during multiple
object tracking: Where do participants look? Cognition, 108(1),
201-209. [ link
]
Updating objects in visual short-term
memory
Previous work has suggested that updating memory is constrained by
properties of attention (Oberauer, 2002). Visual attention is
object-based (Scholl, 2001), as is the storage of information in visual
short-term memory (VSTM; Luck & Vogel, 1997). We investigated
whether updating VSTM is also object-based by determining whether
effects of updating one feature of an object would spread to its
non-updated features. Results showed that the facilitative effect of
updating was specific to the updated feature of an object, and did not
spread to its non-updated features. This feature-selective effect
suggests that updating VSTM is not object-based (Experiment 1), even
though storage was object-based (Experiment 2). Control experiments
ruled out strategy- (Experiment 3) and stimulus-related (Experiments 4
& 5) accounts of the data. These findings indicate that updating
VSTM does not exhibit all properties of attention and support an
account of independent feature representation in VSTM (Wheeler &
Treisman, 2002)
How do we update visual working
memory? When modifying our memory of an object to integrate new
information with stored information, do we use an object-based process
or a feature-based process? Previous work has suggested that updating
is not object-based, but rather feature-selective, because people
selectively update one feature of a memorized object without refreshing
the memory of other features of the object (Ko & Seiffert, 2009 Mem
Cognit). To test whether updating shows any object-based benefit, we
asked participants to update two features of their visual working
memory of either one object or two objects. Participants memorized a
display composed of three colored, oriented bars in three different
locations. The display was followed by a cue instructing participants
to update their memory of one feature of the object at the same
location as the cue. To manipulate whether one or two objects were
updated, a second cue either appeared at the same or different bar
location as the first cue. Also, the two cues were either the same
feature or different features. After the cues, a single bar probe
appeared at one of the three bar locations. Participants indicated
whether the probe matched their memory. The facilitation effect of
updating features did not spread to the other feature of the cued
object or features of other objects, for both one object (interaction
F(1,24)=21.9, p<.001) and two-object (interaction F(1,24)=7.35,
p<.013) updating. This was consistent with previous results showing
feature-selective mechanism in updating. However, when the updated
object was probed, participants performed more accurately when updating
one object than two objects (F(1,24)=29.7, p<.001), showing evidence
for an object-based mechanism. In addition, the feature-selective
facilitation effect was significantly larger in one object updating
than two-object updating (F(1,24)=6.30, p<.02). Taken together,
these results suggested that updating relies on both object-based and
feature-selective mechanisms.
Related Publications: Ko, P. C. &
Seiffert, A. E. (2009). Updating objects in visual short-term memory is
feature-selective. Memory and Cognition, 37(6), 909 - 923. [ link ]
Park, H., &
Seiffert, A. E. (2012). Updating visual working memory is both
object-based and feature-selective. Journal of Vision, 12(??), 442. [ link ]
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