Answer:
Unconditional positive regard.
Step-by-step explanation:
Carl Rogers was one of the founder of humanistic approach and a psychologist.
According to Rogers, Unconditional Positive Regard or UPR is important for a parent and child relationship. UPR, according to Rogers, is accepting and loving without any conditions. He considers this feature important for the growth and development of the child. He thinks that if a child is accepted and loved without any conditions, he is most likely to achieve desires and goal in their life which will lead them to self-actualization.
So, the quality that Alan's parents are withholding according to Rogers is "Unconditional Positive Regard." Which he also termed this quality as "prizing."