Answer:
Regression
Explanation:
Sigmund Freud is considered the father of psychoanalysis which is a school of therapy that focuses a lot in the unconscious and how our early development influences our later behaviors.
According to him, there are defense mechanisms which are defined as the mental processes that are often unconscious and that protects us from anxiety that we would feel if they weren't there. In other words, they protect us from feeling anxious.
One of these mechanisms is called "regression". Regression was actually proposed by Anna Freud and it refers to a process where the ego goes back to an earlier stage of development because of a stressful situation. In other words, the mind of the person goes back to a period where they felt safer and they act as if they were in that period. This mechanism is usually observed in older siblings when a new baby is born.
In this example, 4-year-old Gracie began sucking her thumb again and wanting her mother to rock her, these are behaviors that are seen in younger children and therefore we can see that she went back to an earlier stage of development because her sister was born and this makes Gracie anxious. Thus, this is an example of regression.
