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4 Discussion
The primary aim of the present experiment was to investigate the relationship be-
tween the attention and emotion. We use dynamic facial expressions as the emotional
stimuli, which are natural and frequently encountered in everyday life. The spatial
attention was manipulated by instructing the participants to pay attention to one side
of the screen thus maintain the attended focus at the certain location. The probability
of the stimuli is another complement to control the spatial attention. In each block,
75% stimuli were present at the attended side. A sustained attention paradigm was
employed (with left/right side attended tasks delivered in separate experimental
blocks).
It is predictable that the process will be slower when the stimuli appear outside the
current focus of attention. This is confirmed by the gain of RTs to the stimuli at
the attended location comparing with unattended location. The question is whether the
emotional expressions are processed pre-attention or automatically.
The emotion is a task-irrelevant factor in this experiment. Participants only have to
detect the interruption within the expression, which is a simple physical detection
task. If the emotion processing is not automatically, the attention effect will be the
same to any type of expressions regardless the emotion valence. That means the de-
cline of the attention absence to the neutral expressions will be the same with the
emotional expressions. But the results turned out to be the opposite. It took more time
to distinguish the stimuli when the neutral expression appeared outside the focus of
attention. But increased cost didn't change significantly when the emotional expres-
sions appeared outside the attention. It implies the emotion information speedup the
processing even it is irrelevant to the ongoing task. The result supports the notion that
emotion can be processed automatically. The emotion expression drew the attention
automatically, which proved the attention bias to emotional objects again.
However, our results are not enough to draw the conclusion that the emotion proc-
essing is pre-attention. Comparing with the previous studies, evidence for the process-
ing of emotion stimuli that are outside the focus of attention is mixed. The present
result is consistent with some previous study including behavioral experiments, ERPs
and fMRI studies. Many fMRI studies pay attention on the respond of amygdala to the
fear, and other related area, such as superior temporal sulcus (STS), fusiform cortex
[5]. A left amygdala response to fearful compared to neutral faces occurred regardless
of whether the faces were at relevant/attended locations or at the irrelevant/ unat-
tended locations, demonstrating that fear processing in the amygdala was obligatory
and unaffected by the modulation of spatial attention.
The mixed conclusion can be related to the spare processing capacity that is util-
ized for the processing of task-irrelevant or unattended items. The studies that re-
vealed that attention modulates the processing of emotional stimuli employed very
demanding tasks that might have nearly exhausted the processing capacity. By con-
trast, the studies that observed little or no effect of attention used less demanding
tasks. The task in this experiment is relative simple and with little processing resource
involved as our design. It was proved by the high accuracy and the participants'
