Scientists believe that facial expressions may influence our emotions, meaning that those whose faces can’t move naturally may feel less emotion.

To test this, researchers at Columbia University treated 68 women, ages 27-60, with either Botox (a filler that paralyzes facial muscles) or Restylane (a filler that has no effect on facial muscles). Before and after treatment, the women watched a series of positive and negative video clips, and rated their emotional response.

After treatment, the Botox group felt less emotion, compared to the Restylane group. More specifically, their emotional reaction was much weaker for mildly happy clips. That means facial expression may matter most when the emotion is weak (and most easily influenced by external cues).

Looks like it’s all the little moments—like a sunny day or a nice compliment—that take the biggest hit.