 According to a  study done by Kopel Arkowitz(1974), Kopel, S. A., & Arkowitz, H. S. (1974).
<meaning-changed>  According to a  study done by Kopel Arkowitz(1974), Kopel, S. A., & Arkowitz, H. S. (1974).
 According to a study done by Kopel and Arkowitz, repressing the facial expressions associated with pain actually decreased the experience of pain in participants. Kopel, S. A., & Arkowitz, H. S. (1974).