January 23, 2016 at 12:12AM

Today I Learned: 1) Babies are weird. Like, more than I knew. Item 1: Young babies perceive the world through a much clearer eyeball than we adults, and are much more sensitive to light. Item 2: Babies hear echos, always, generated by the difference in timings between each ear receiving a new sound. Your ears pick up the same echo, but somewhere in your auditory pipeline you learn how to process these echos into a single coherent sound (with directionality). Don't ask how we know this. I'm just trusting Radiolab on this one. Item 3: Babies under brain scans sometimes, apparently at random, will respond to stimulus as though they experienced a stimulus of a different modality. For example, a baby might be shown a circle but its brain will light up as though it heard a sound (and presumably it *does* hear a sound). 2) You know how you can add the voltages of batteries together by wiring them up in series? Turns out you can also *subtract* voltage from a battery by wiring it to another battery in series, but backward. 3) There is probably almost never a reason to run PCRs for more than 25 cycles. A quick back-of-the-envelope calculation shows that you run out of primers sometime around then under ideal conditions (though I've read from some people who studied PCR quite extensively in the 90s that primers are never limiting in PCR....), and everything you amplify after that is off-target messy stuff.