The Role of Suppression in

1
The Role of Suppression in
Jason Barker, Lea Hald Janet Nicol
Department of Psychology - University of
Arizona - Tucson, Arizona
Results
Conclusions
Tasks
Introduction
Inhibitory processes play a central role in many
current models of language and memory.
Gernsbacher and colleagues (see Gernsbacher
Faust, 1995 for a review) have conducted a number
of studies specifically investigating the
importance of inhibiting or suppressing
irrelevant information during the course of
language processing. Using a simple semantic
interference task to assess suppression skill,
they have demonstrated that this ability is
related to overall comprehension skill,
successful inhibition of incorrect forms of
homophones, and quickly identifying the correct
target of anaphoric reference. They have also
found relationships with non-linguistic tasks,
such as the tendency to report typical, but
absent, objects from visual scenes.

Suppression Task. We used a task modeled on
Gernsbacher et. al. (1991) Lewis and colleagues
3,4 measured the monocular visual field extent of
3-, 4-, and 6-month-old infants using 6-Hz
flickering or non-flickering lights. The results
showed larger measured visual field extent for
flickering stimuli than for non-flickering
stimuli in 3- and 6-month-old infants in the
temporal visual field, but not in the nasal
visual field. No effect of flicker was reported
for 4-month-old infants in either the temporal or
nasal visual field.
Peripheral stimulus flicker enhanced measured
visual field extent for both the 3.5- and
7-month-old infants when a 10 Hz flicker rate was
used. However, when a 3 Hz flicker rate was used,
an effect of flicker was found only in the
temporal direction and not in the nasal
direction. We found no effect of flicker in the
adult subjects.
Temporal visual field analysis. In the temporal
direction, measured visual field extent in
infants was significantly smaller (plt0.05) for
the non-flickering stimuli than for both the 3 Hz
and 10 Hz flickering stimuli. Temporal visual
field extent did not differ between the 3 Hz and
10 Hz flickering stimuli. Stimulus flicker did
not affect measured visual field extent in
adults.
References

• Bock Miller (1991) Broken Agreement. Cognitive
  Psychology, 23, 45-93.
• Eberhard, K.M. (1997). The Marked-Effect of
  Number on Subject-Verb Agreement. Journal of
  Memory and Language, 36, 147-164.
• Gernsbacher, M.A., Faust, M. (1991). The
  mech- anism of suppression a component of
  general comprehension skill. Journal of
  Experimental Psychology LMC, 17, 245-262.
• Nicol, J.L., Forster, K.I., Veres, C. (1997).
  Subject- verb agreement processes in
  comprehension. Journal of Memory and Language,
  36, 569-587.

Methods
Subjects. Subjects were 24 University of
Arizona undergraduates who received course credit
for participation. All were native speakers of
English.
Apparatus. The apparatus was a black double-arc
perimeter, with 3.5-cm-wide

arms that extend to 110? along the 45?, 135?,
225?, and 315? half-meridia. Yellow, 3-diameter,
flickering or non-flickering LED stimuli were
used.

• Procedure.
• Subjects were positioned with their eyes 36 cm
  from the central fixation stimulus which was
  extinguished once the peripheral target was
  illuminated.
• The fixation stimulus, located at the
  intersection of the four perimeter arms,
  consisted of a 6?-diameter ring of eight yellow
  0.6? LEDs.
• An observer, hidden behind a black curtain
  reported the childs eye movements.
• Adults were instructed to fixate the central
  stimulus, and then identify the location of the
  peripheral stimulus.
• Each subject was tested with sixteen trials, one
  trial at each of four locations on each of the
  four perimeter arms.
• One-third were tested with a 3-Hz flickering
  stimulus.
• One-third were tested with a 10-Hz flickering
  stimulus.
• One-third were tested with a non-flickering
  stimulus.

Nasal visual field analysis. In the nasal
direction, measured visual field extent in
infants was significantly smaller (plt0.05) for
the non-flickering stimuli than for the 10 Hz,
but not the 3 Hz flickering stimuli. Nasal visual
field extent did not differ for 3 Hz and 10 Hz
stimuli. Stimulus flicker did not affect measured
visual field extent in adults.
Do flickering stimuli result in significantly
larger measured visual field extent?
Flicker rate Flicker rate Flicker rate Flicker rate
3 Hz 3 Hz 10 Hz 10 Hz
Nasal Temporal Nasal Temporal
3 Months No Yes Yes Yes
7 Months No Yes Yes Yes
Adult No No No No
Acknowledgements
This work was supported in part by National
Multipurpose Research and Training Center Grant
DC-01409 from the National Institute on Deafness
and Other Communication Disorders, and by the
Cognitive Science Program and Dept. of Psychology
at the University of Arizona.