Exhibit 15.17 Activity in the left/right-frontal brain reveal approach-avoidance tendencies. (Source: adapted from iMotions,
image from Wikipedia).
The frontal asymmetry reveals insights into the subject’s
motivations, emotions and engagement. As depicted in
Exhibit 15.17, increased activity in the left-frontal indicates positive feelings, engagement and motivation, and the reverse
is true for the right-frontal. This relationship serves as a useful index of approach and avoidance:
$$ Frontal \,Asymmetry \,Index \,(FAI) = log \left(\frac {alpha \,power \,right \,F4}{alpha \,power \,left \,F3}\right) $$
A higher FAI typically indicates a positive disposition to stimuli, while a
lower index indicates a negative disposition. This metric is derived by extracting signals
from the electrodes F3/F4 and F7/F8.
In addition to the FAI, the beta (12-25 Hz) or gamma (> 30 Hz) band power,
particularly in the frontal cortical regions (electrodes F3 and F4), are good indicators
for the motivation towards (approach) or away from (avoidance) any stimulus.
These metrics are used for evaluating advertising and packaging, as well as
for product testing. They provide an unbiased indicator of the respondent’s emotional and
motivational disposition towards a new product.
