Answer:
fMRI studies on emotional reactivity to happy facial expressions have found that:
* The amygdala, a brain region involved in processing emotions, is activated when people see happy faces.
* The orbitofrontal cortex, a brain region involved in decision-making and social cognition, is also activated when people see happy faces.
* These activations are stronger in people who are more extroverted and who have more positive social interactions.
* People with autism spectrum disorder show reduced amygdala and orbitofrontal cortex activation in response to happy faces.
These findings suggest that the brain's response to happy facial expressions is complex and involves a number of different brain regions. The strength of these responses may be influenced by individual differences in personality and social experience.