endogenous smile

a spontaneous or reflexive smile that is observed when an infant, early in life, is in a state of REM sleep. Characterized by a simple turning up of the corners of the mouth, such smiles are seen from birth and are not elicited by social stimulation. Compare social smile.

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Psychology term of the day

July 27th 2024

trinucleotide repeat

a contiguous repetition of the same three nucleotides within a nucleic acid (DNA or RNA). The occurrence of extra trinucleotide repeats in certain genes causes dysfunction, inluding Huntington’s disease and fragile X syndrome.