Answer:
frontal
Step-by-step explanation:
Frontal lobe: The term frontal lobe is referred to as a part of the brain which is responsible for controlling significant cognitive skills of human beings, for example, problem-solving, expression, judgement, language, sexual behaviors, and memory etc. It regulates the control panel of an individual's personality and his or her ability to communicate.
If the frontal lobe of a person gets damaged then the person faces the memory impairment, increased irritability, and inability to regulate behavior etc.
In the question above, the statement states the incomplete development of the frontal lobe.