Behavioral scientists have long noted that the Ekman Neutral face stimuli are often rated as anything but ‘neutral.’ While it is sometimes assumed this is inherent to the stimuli themselves, it is also possible that individual biases or states determine some of this variability (these points are not mutually exclusive).
The Figure presented here presents data from our recent study [see Somerville et al (2004) in the Publications link]. While subjects viewed alternating blocks of Happy and Neutral faces, their amygdala responses to the Neutral faces were related to individual differences in their levels of state anxiety. Since anxiety can be related to greater vigilance for threat, it may make sense that more anxious subjects were more responsive to the most potentially threatening face stimulus in this experimental paradigm, namely Neutral faces.
Our future studies will aim to determine the extent to which this effect can be generalized to different experimental paradigms (i.e., does this effect depend upon the presence of alternating happy face blocks). Further, an additional caveat is that since this is an fMRI finding, we cannot know with absolute certainty whether this effect demonstrates that state anxiety is related to ‘response’ to Neutral faces, or represents a shift in the ‘resting’ baseline across these subjects.