Ah, puberty. A time for raging hormones, growing independence and being stupid. Okay, not every teenager gets stupid. But they actually do learn less. And in a study published in the journal Science, researchers describe the cellular and molecular changes that drive this puberty-associated desmartification. Learning happens in the hippocampus, a brain region that plays a key role in acquiring memories. From a cellular perspective, learning takes place when the connections between nerve cells are strengthened. Interfere with those stronger neuronal connections, and a brain can have trouble laying down new memories. Which, apparently, is what happens in adolescence. At least in mice. Scientists used a variety of methods to study the brains of pubescent female mice. And they discovered that a particular protein, a kind of GABA receptor, for those of you keeping score at home, crops up in the hippocampus during puberty. These receptor proteins interfere with neuron communication and thus prevent the sort of synaptic strengthening these young animals need to learn. The good news: a hormone that quiets this pubescent protein turns these young animals back into better learners. Imagine, a hormone that actually makes an adolescent act smarter.