There are plenty of psychology concepts that I will need to use later in life: the theories of learning for teaching and raising children, the "Big Five" personality traits, and the three stage theory of memory. But what interests me most on a purely "cool" level is the development of infant psychology.
Meanwhile, watch this cute baby use sticky mittens. It's cute because it is hilariously uncoordinated.
I find it completely fascinating at how simple tasks are impossible for infants and even young children. It's hard for us to imagine not having a "theory of mind" to understand other points of view. Equally as astonishing is how fast these mental abilities develop in children and how relatively universal the age is that these developments unfold at. My niece is still a baby, and it will be interesting to watch her develop when I know certain milestones that occur.
While I feel that infants are very simple in regards to my previous examples, I can still marvel at how complex of a learning machine they are. The study of universal adaptability towards phonemes shows how powerful the human brain is even at a young age. From now on, I won't look at a baby as a small, babbling ball of soft flesh. It is a learning machine, just as complex as we are.