 In a study done by Kleck et al. in 1976, participants were told to suppress facial expressions of pain during the reception of electric shocks.
<clarity>  In a study done by Kleck et al. in 1976, participants were told to suppress facial expressions of pain during the reception of electric shocks.
 In a study done by Kleck and colleagues in 1976, participants were told to suppress facial expressions of pain during the reception of electric shocks.