“Processing Affective Images in the Absence of Visual Awareness.” Nicholas Hedger

Nicholas Hedger (Reading University)

“Processing Affective Images in the Absence of Visual Awareness.”

Scientists and lay-people alike have long been fascinated by the notion that affective
visual stimuli have a ‘special’ status within the brain. Neurocognitive theories suggest
that humans have evolved specialised mechanisms that operate without awareness
and selectively promote the perceptual selection of threatening stimuli. Evidence for
this ‘standard hypothesis’ comes primarily from paradigms that dissociate visual
input from awareness, such as backward masking and continuous flash suppression.
Findings from these paradigms have demonstrated that affective stimuli suppressed
from awareness can nonetheless modulate our behaviour and physiology in ways
consistent with fear arousal. Although this evidence base has grown, so too has
scepticism. Here, I provide a critical review of this literature, with reference to my
own experimental and meta-analytic studies. The findings converge on two central
ideas – namely: the processing of threatening stimuli is i) restricted to, or associated
with conditions of awareness ii) parsimoniously explained by low-level variability
between stimuli. It is concluded that evidence for threat-sensitive visual processing
that operates without awareness is weak and that uncritical acceptance of the
standard hypothesis is premature