Renée K. Biss and Lynn Hasher, “Happy as a Lark: Morning-Type Younger and Older Adults Are Higher in Positive Affect,” Emotion 12, no. 3 (2012): 437–441.
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Ryan J. Walker et al., “Age, the Big Five, and Time-of-Day Preference: A Mediational Model,” Personality and Individual Differences 56 (2014): 170–174; Christoph Randler, “Morningness-Eveningness, Sleep-Wake Variables and Big Five Personality Factors,” Personality and Individual Differences 45, no. 2 (2008): 191–196.