Robert Zajonc was an outstanding American social psychologist (1923-2008).

Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of Personality and Social Psychology, 9(2, Pt.2), 1–27. https://doi.org/10.1037/h0025848

Author describes the concept of mere-repeated-exposure and how an individual repeatedly exposure to a particular object affects the individual’s emerging preference for that object. Author reviews publications which show the mere exposure effect as a robust phenomenon even without participants’ awareness. The effect is valid across cultures, species, and diverse objects domains. Research shows that an experience of repetition enhances positive affect not only to the same objects, but also to similar objects, and to other distinct objects.

Zajonc, R., Adelmann, P., Murphy, S., & Niedenthal, P. (1987). Convergence in the physical appearance of spouses. Motivation and Emotion, 11, 335-346.

McIntosh, D. N., Zajonc, R. B., Vig, P. S., & Emerick, S. W. (1997). Facial movement, breathing, temperature, and affect: Implications of the vascular theory of emotional efference. Cognition and Emotion, 11(2), 171–195. https://doi.org/10.1080/026999397379980