Doebel and Munakata (2018) discovered that delay of gratification by children is influenced by social context. All children were told that they were in the “green group” and were placed in a room with a single marshmallow. Participants were told that they could either eat the single marshmallow now or wait for the experimenter to return with two marshmallows. Before choosing between one marshmallow now or two later, children were randomly assigned to one of two conditions. They were told that either (1) other children in the green group waited and kids in the orange group didn’t wait or (2) other children in the green group didn’t wait and kids in the orange group waited. Children were more likely to choose to wait after being told that other members of their group waited.

a. Did this study use experimental or nonexperimental methods?

b. Identify the variables in this study.