Expression of emotion
Toddlers can cycle through emotions quickly, being (a) extremely happy one moment and (b) extremely sad the next.
Source
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"CNX Psychology, Psychology. July 28, 2015."
http://cnx.org/contents/4abf04bf-93a0-45c3-9cbc-2cefd46e68cc@4.100:58/Psychology
OpenStax CNX
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