Note 109 — Chapter VI · THE ORIGIN OF LAUGHTER.
Reading edition
A. Lehmann, in his interesting account of the development of the emotions and their expression in the individual, suggests that the first imperfect smile of the infant, which expresses the pleasure of sweetness, is genetically related to the movements of sucking (Hauptgesetze des menschl. Gefühlslebens, ss. 295, 296).