Final answer:
The child's behavior of yelling at the babysitter when actually angry with their mother is an example of the defense mechanism known as displacement.
Step-by-step explanation:
The scenario described involves a child redirecting anger towards a baby sitter instead of the actual source of anger, which is the mother. This behavior is an example of a psychological defense mechanism known as displacement. Displacement occurs when a person cannot direct their emotions towards the true source of those emotions (usually because it is unacceptable or threatening) and therefore transfers, or displaces, them onto a safer or more acceptable substitute target.
In this case, the child is using displacement as a way to handle the anger felt towards their mother by expressing it towards the baby sitter, who is likely viewed as a less threatening recipient of the child's anger. This defense mechanism protects the child's ego by allowing them to vent their feelings without directly confronting the more intimidating figure of the parent.