Through an array of cleverly designed studies, developmental psychologists have demonstrated that human beings do not come into the world as "clean slates," empty of ideas and waiting for the world to make its imprint upon them. In actuality, infants and young children show a remarkable ability to understand the world around them. They possess powerful “rules of thumb” that allow them to make sense of their earliest encounters with the world and extract enormous amounts of information from those encounters. Were it not for these rules of thumb, our development would take far longer and we would likely find ourselves lost in confusion for many years of our young lives. Three of these rules, which developmental psychologists call "cognitive constraints" are particularly relevant to learning about evolution. Each one, while highly useful in many situations, makes learning about evolution challenging. Our brains have evolved to help us survive and make our way in daily life, not to contemplate complex scientific theories. And some of these theories, like evolution, are counter-intuitive according to these rules.
The first is the essentialist constraint As several of our contributors have shown through the work (Margaret Evans, Susan Gelman, Karl Rosengren, and Andrew Shtulman), essentialism influences children's thinking by encouraging them to believe that the things we see in the world belong to immutable categories, having an essence that cannot be altered. You can paint stripes on a raccoon to make it look like a skunk, but children won't be so easily tricked. They know that it will still have raccoon babies; paint cannot overcome its "raccoon essence." Likewise, a dinosaur cannot become a bird, an aquatic creature cannot morph into one that walks on land. Even adults will show this tendency to think of creatures as having immutable essences, especially when under time pressure, or when they have a lot on their mind, or when they encounter something truly novel.
Of course, this directly contradicts evolutionary theory, where change through random variation is the prime mover and selection a filter that determines the fate of these changed creatures. The cognitive constraint that allows a child to assume that the world will not suddenly shift under their feet is terribly useful for everyday thinking, but makes thinking in evolutionary terms terribly difficult.
A second constraint is the teleological constraint. Children and even adults show this tendency--to assume that everything, including living creatures have a specific form and function for a reason. Birds have wings because they need to fly; we have eyes because we need to see. Instead of the evolutionary account of these developments--that selection pressures gave advantages to those with eyes and wings and allowed them to survive, children and adults are inclined to see these features as being the product of a goal-driven design. Being able to find and understand the purpose of a thing is very helpful to us as youngsters, as we figure out how the causal world works, but it sets us up to find design-based accounts of change more plausible than directionless evolution.
The third and final constraint is intentionality. Our young minds go further than just finding a purpose for the existence of such features as eyes and wings. They tend to believe that these features were created by an intentional agent, whether those intentions come from a supreme being, the creatures themselves, or another agent with the ability to think, decide, and enact a particular vision of the world. Again, not a bad assumption at all when trying to figure out why things happen in the world, but completely at odds with evolutionary mechanisms.
Even parents who accept evolution and know, at some level, that these constraints do not apply in the case of biological evolution, will reinforce these beliefs in their children. Adults are extremely good at adjusting the way they explain things to a child, and use the child's view of the world to help them understand what they see when they are at a museum, say, or the zoo. A parent can be overheard saying that the giraffe has a long neck because it needed one to eat from the highest branches of a tree. The dinosaurs became extinct because they were not made to withstand the strains and stresses of the world around them.
Thus, by the time we reach school-age, we have a very good model of how the world works, but it is one in which evolution is completely counter-intuitive and perhaps downright silly.