Amusement

Amusement is the expression of finding something entertaining, pleasurable or funny.

Amusement is reached through surprise at a positive thing. When a person is surprised (the less intense version of astonishment), the instinctual reaction is a preparation for another emotion. The eyes and mouth moderately open in coordination with each other in a fluid motion. The heart rate increases a few beats a minute as a little gasp of air is drawn and then held.1
When the surprising event turns out to be positive, the expression morphs into amusement. The eyebrows lower, the eyes softly reduce in size, and the moderately open mouth widens into a faint smile. This is often accompanied with a barely perceptible exhalation, a sigh of relief or a chuckle. When no harm befalls the persons concerned, people often find the mistakes that others make through inexperience amusing.
A mother watches as her toddler waddles by a wall mirror for the first time and shrieks in astonishment at his reflection. He freezes when the little person in the mirror shrieks too. Cautiously moving forward to greet the boy in the mirror, the toddler puts his hand up to the stranger’s face. The little boy in the mirror does the same, and it startles him. Slowly the index finger is near the boy’s in the mirror and their fingers meet. Puzzlement ripples through the toddler’s mind as he finds the sensation solid and cold – not like a finger at all. While having the notion that the toddler in the mirror is not real, he slaps the mirror and shrieks once again. There’s no reaction, only a strange symmetry. Chuckling with amusement, the mum watches as her toddler waddles to the corner of the wall mirror, peeks behind it, and then looks back at her with a wide-eyed smile of amazement.

A brief expression of surprise can be seen milliseconds before the smile of amusement adorns the mother’s face. The word comes from muse, which means a diversion to think upon.

Amusement

Middle French. Amuser = divert, cause to muse.

1. The state of being entertained, or pleased.

2. Finding something funny.