The establishment of positive and negative evaluative conditioning reflex of neutral facial expression

Objective To examine the effect of positive and negative evaluative conditioning (EC) on neutral faces. Methods The experiment consisted of three phases: baseline phase, conditioning phase, and re-evaluative phase, in which 41 college students participated, watching sequences of neutral faces (CS) pairing to either a positive stimulus (USpos) or a negative stimulus (USneg). Their emotional experiences (valence and arousal) and physiological reactivity (eyeblink startle reflex and skin conductance) were recorded. Results (1)In the re-evaluative phase, CSpos was rated significantly more positive than CSneg and CSneut, while CSneg was rated significantly more negative than CSneut (CSpos (5.05±1.24), CSneg (3.73±1.48), CSneut (4.46±1.04), P<0.05). (2)In the re-evaluative phase, the mean startle eyeblink response magnitude(T score) to CSpos was significantly smaller than the responses elicited by CSneg and CSneut (CSpos (45.04±5.56), CSneg (51.44±9.30), CSneut (54.52±10.60), P<0.01). Conclusion The findings suggest that neutral faces can acquire valences and approach motivation through EC. Key words: Facial expression; Neutral face; Evaluative conditioning; Eyeblink startle response; Subjective rating