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```Attentionally Dependent Bilateral Advantage on Numerosity Judgments
Jenny Ewing &amp; Nestor Matthews
Department of Psychology, Denison University, Granville OH 43023 USA
Introduction
Stimuli in One Color Condition
Stimuli in Two Color Condition
Series of Stimuli and Questions
1. Which letter appeared
in the center of the screen?
P
O
Q
W
Q
2. Were the numerosities in
same or different?
Study 2
•IVs: 2 (Laterality) x 4 (Day) x 2 (Color)
•Laterality: All trained unilaterally on days 1, 2, &amp; 3
•Day 4: Half tested unilaterally, half bilaterally
•Day: 1 - 4
•Color: Half saw only 1 color, half saw 2 dot colors
•DV: Proficiency (d’ / RT)
•Stimulus shown for 200 milliseconds.
Study 1
•IVs: 3 (Laterality) x 2 (Color)
•Laterality: Bilateral vs Unilateral vs Diagonal
•Color: One dot color versus Two dot colors
•DV: Proficiency (d’ / RT)
•Hits: “Different” response when number of dots
differed
•False Alarms: “Different” response when number of
dots was the same.
•Dot diameter: 1.6 cm
*
Results
Study
2
*
Study 1
*
Proficiency Two Colors over Four days
3.5
2.5
0.7
y = 0.9026x0.5981
R&sup2; = 0.9909
0.6
3
y = 1.0495x0.6541
R&sup2; = 0.9695
2
0.4
0.3
One
Two
0.2
0.1
2.5
1.5
Unilateral
Bilateral
1
y = 0.7964x0.643
R&sup2; = 0.99
*
0
Diagonal
Laterality
Unilateral
Laterality: F (2, 48) = 15.753, p &lt;. 001, pEta^2= .396, power=.999
Color: F(1,24)=3.241, p=.054, pEta^2=.119, power=.48
Laterality x Color: F(2,48)=19.106, p,.001, pEta^2=.4438, power=1
2 Color Bi vs. Uni: t(24)=7.561, p&lt;.001
0
0
1
2
Day
2
Unilateral
Bilateral
1.5
1
0.5
Bilateral
Proficiency score
0.5
3
4
Although we observed bilateral superiority on the two-color
condition in experiment 1, that effect did not replicate on either color
condition in experiment 2.
Within each of the four (color by laterality) groups in
experiment 2, significant learning occurred. The learning transferred
completely from the trained to the untrained laterality. This complete
transfer contrasts with most previous perceptual learning studies, which
typically have shown practiced-based improvements that are specific to
the trained conditions. The difference likely reflects the fact that the
present stimuli, task, and spatial positions were identical in our training
and test phases -which differed only in the attended laterality (unilateral
versus bilateral). The complete transfer observed here suggests that the
attended laterality was NOT the factor which limited performance.
The present study required enumeration by proximity within
has been shown to generate bilateral inferiority in shape-discrimination
(Pillow &amp; Rubin, 2002), presumably reflecting time to cross the corpus
callosum. A comparable cost for similarity-based enumeration would
suggest that proximity and similarity are affected differently by
laterality.
References
Proficiency One Color over Four Days
Proficiency
Proficiency Scores
Operational Definitions: Laterality is a variable that describes
the spatial distribution of stimuli. Unilateral stimuli are restricted either
entirely to the left hemifield, or entirely to the right hemifield. Bilateral
stimuli are distributed across the left and right hemifields. Attention is
the selection of a sensory event. Perceptual learning –in vision- is any
practice-driven improvement in visual ability.
Several previous studies support the premise that laterality affects
attention. Specifically, a bilateral attentional advantage has been reported
on several attentional tasks. These include motion tracking (Alvarez &amp;
Cavanagh, 2005), letter identification (Awh &amp; Pashler, 2000), letterorientation discrimination in displays that exhibit crowding (Chakravarthi
&amp; Cavanagh, 2009), and detecting Gabor targets while ignoring Gabor
distractors (Reardon, Kelly &amp; Matthews, 2009). A preliminary study
also indicated a bilateral advantage for numerosity judgments
(Delvenne et al., 2009).
The premise that attention affects perceptual learning is
supported by studies showing practice-driven improvements for attended,
but not unattended, features of a given training stimulus. Such
attentionally specific perceptual learning has been reported for a variety
of features: Luminance vs orientation (Shiu &amp; Pashler,1992); local vs
global orientation (Ahissar &amp; Hochstein, 1994); direction of motion vs
speed of motion (Saffell &amp; Matthews, 2003).
Synthesizing those prior findings, here we tested the prediction
that laterality affects perceptual learning –with attention as the mediating
factor. Building on Delvenne et al. (2009), laterality was investigated
while participants judged the numerosity of dot ensembles having a
single color, or two colors. The two color condition was designed to
reduce similarity-based perceptual grouping, thereby increasing the
attentional load and the concomitant bilateral superiority. All participants
trained unilaterally for three days. On the fourth day, participants were
tested either unilaterally again, or bilaterally for transfer of learning.
Measuring transfer was particularly interesting, as the stimuli, task, and
spatial positions were identical in our training and test phases -which
differed only in the attended laterality (unilateral versus bilateral).
Discussion
Method
Proficiency (d'/reaction time)
The Motivating Syllogism
Premise 1 - Laterality affects attention.
Premise 2 - Attention affects perceptual learning.
Prediction - Laterality affects perceptual learning.
Poster Session III
Board III - 022
y = 0.914x0.6363
R&sup2; = 0.9884
0.5
0
0
1
2
Day
3
Learning (day 1-day 4): F(1,42)=189.00, p&lt;.001, pEta^2=.82, power=1
Laterality (one color-Bi vs. Uni): F(1,19)=.09, p=.76, pEta^2=.01, power=.06
Laterality (two color-Bi vs. Uni): F(1,20)=.862, p=.364, pEta^2=.04, power=.143,
4
Ahissar &amp; Hochstein (1993). Attentional control of early perceptual learning.
Proceedings of the National Academy of Sciences, 90(12), 5718-5722.
Alvarez, G. &amp; Cavanagh, P., (2005). Independent Resources for Attentional Tracking in
the Left and Right visual Hemifields. Psychological Science, 16(8), 637-643.
Awh, E., &amp; Pashler, H. (2000). Evidence for split attentional foci. Journal of
Experimental Psychology: Human perception and performance, 26(2), 834846.
Chakravarthi &amp; Cavanagh (2009). Bilateral field advantage in visual crowding. Vision
Research, 49(13), 1638-1646.
Delvenne, J.F., Castronovo, J., Demeyere, N., &amp; Humphreys, G. (2009).
Enumerating visual items within and across hemifields. Vision Sciences
Society, 63.406, (abstract).
Pillow, J., &amp; Rubin, N., (2002). Perceptual Completion across the Vertical Meridian
and the Role of Early Visual Cortex. Neuron, 33, 805-813.
Reardon, K., Kelly, J., &amp; Matthews, N., (2009). Bilateral Attentional advantage on
elementary visual tasks. Vision Research, 49(2009), 691-701.
Saffell, T., &amp; Matthews, N. (2003). Task-specific perceptual learning on speed and
direction discrimination. Vision Research, 43(12), 1365-1374.
Shiu &amp; Pashler (1992). Improvement in line orientation discrimination is retinally local
but dependent on cognitive set. Perception &amp; Psychophysics, 52(5), 582-588.
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