Is the baby trying to learn more about his or her environment and is fussier and sleeping lesser during the leap?

Yes, I think it is largely due to the fact that they are learning new information and developing mentally which causes them to be fussier. It is a complicated process where they begin to comprehend a new "idea" (in a way, e.g., learning about patterns). To understand more about what babies begin to understand at each leap, you can refer to this brief summary: http://www.babysleepsite.com/baby-sleep-patterns/wonder-weeks-chart-baby-toddler-sleep/ Will give you an idea what the baby may be going through and allow you to help comfort your baby better. :)