Emotions are physiological. The muscles is linked to feeling emotions. For example: those who have Botox injections have less emotional reactions. This is a direct correlations between lack of muscle movement. Frowning and smiling increase the feeling of emotions.
The Brain Mirrors Emotions
People experience others' emotions. If someone is smiling or frowning, someone looking on will feel that emotion. When people are in similar situations, the same region in the brain is activated. Avoid unintentional facial expressions in your designs/advertisements. This may cause a different emotional reaction than you had intended.