Definition: Downward comparisons are one type of social comparison, or an assessment of how we measure up against our peers. When we make downward comparisons, we judge ourselves against people who are less skilled or fortunate than ourselves. For instance, a tween who is struggling in soccer might compare himself to the worst player on the team and think, "Well at least I can block better than he can." Downward comparisons are the opposite of upward comparisons.
It would be detrimental if a child made only downward comparisons and no upward comparisons; in that case the child might not strive to be better and might develop an unrealistic, over-inflated sense of self. At the same time, a surplus of upward comparisons can also be problematic since downward comparisons serve to protect self esteem.
Parents can encourage their children to judge their own efforts and circumstances relative to their past self rather than relative to others. That said, social comparisons happen naturally and do not need to be negative, especially if a balance is struck between upward and downward comparisons.
Myers, David G. Social Psychology, 10th edition. New York: McGraw-Hill.