How the Brain Works The Facts Visually Explained by DK (z-lib.org)

COMMUNICATION

Expressions 116 117

Smiling

A smile can either be a genuine

expression of positive mood or a

conscious, socially motivated action.

Genuine smiles are unconscious

acts that involve different muscle

groups to social smiles. While both

involve a stretched mouth with lips

upturned at the corners, the genuine

smiling person constricts muscles

that raise the cheeks, producing

“crow’s feet” around the eyes.

Conscious smiles vary in their exact

structure and are used in an array

of social interactions—they can be

socially bonding but also used to

signal dominance, and people may

also smile to mask embarrassment.

Genuine smile

The muscular contractions involved in genuine

smiles are triggered by signals from the brain’s

emotional centers, such as the amygdala,

usually operating without our awareness.

The distinctive fearful expression

includes raised eyebrows, wide eyes,

and the mouth falling open. This signals

others to be on high alert.

When we are happy, we raise the

corners of our mouths and also raise

our cheeks—the skin under the eyes

wrinkle, and the eyes are said to sparkle.

In surprise, people quickly open their

eyes wide and arch their brows, while

their lower jaw drops, leaving the

mouth agape.

Conscious smile

Conscious control of social smiling involves

activation of the frontal cortex and signals

from the motor cortex. The mouth muscles

contract, but we can’t control the eye muscles.

Motor cortex

Frontal cortex

Signal causes muscles

around mouth to contract

and pull lips sideways in

both types of smiles

Motor cortex

Amygdala

Signal causes small muscles

around eye socket to contract

Raised cheeks Raised brows

Jaw dropped

Eye widening and

other features are

common to early

stages of expressing

fear or surprise

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