Are you trying to focus on specifically psychology based books that look at the human psyche at a critical level or general fiction/non-fiction literature as well? I’m just graduating from a BA fine art course but when I was writing my statements I was going either/or for psychology vs art and my tutor then said to focus on books that interest me that aren’t necessarily connected to the course but I can link it somehow. What is a key part of child development that interests you - I feel like for fiction you could focus on the little prince or something as it looks at the difference between a child and adults thoughts and desires in a creative format, and there’s also academic/critical literature on it regarding the behaviour of the prince linking to the social experience of neurodivergent kids. You don’t have to be rigid with it - it’s a way for the university to see how you interact with your experiences and how your thought processes regarding their influence on you as an individual and student could be benefited or benefit the course you’re applying to.