Melanopsin enhances image persistence.

Scientific advances are often framed as a triumph of prediction and will, a fait accompli, or an inevitable culmination of a journey of genius. Though as guilty of this type of framing as my colleagues, I instead aim here to tell a different kind of story about a scientific mistake which led to a better-than-expected outcome. Part of the moral of this story is that for scientific progress, curiosity, openness, and a supportive environment can matter at least as much as intellect or planning (and a metamoral is to keep good notes, given the fallibility of memory). The story begins on April 20 of 1996, in a darkened laboratory room in the center of the fifth floor of a brutalist brick psychology building facing the windswept plains on the edge of Bowling Green State University in Ohio. I had returned to this room after retrieving two juvenile rats from singly-housed cages in a nearby colony room. Under red light, I placed them together into a clear Plexiglas box inside a sound-attenuated chamber and shut its windowed door. While watching the pair sniff around the chamber, I dialed a frequency (around 20 kHz) into a small device shaped like a handheld transistor radio with a narrow cylinder protruding from its top (called a “bat detector”; ). Next, I pointed the bat detector towards the chamber and donned a pair of connected headphones. Like nails on a chalkboard, a piercing screech assaulted my ears. Frantically, my thumb scrambled to dial down the volume on left side of the device. To my relief, the screech died down into a quieter background hiss (later investigation suggested that a nearby refrigerator storing isotopes was the likely culprit generating the artifactual shriek). By now, the rats had begun to play, making tentative “dorsal contacts” by hopping onto each other’s necks in bids to “pin” or flip them over onto their back, in a manner not unlike human Greco-Roman wrestling. After a pin, the pair would typically pop up and chase each other around the chamber to initiate the process again (Poole & Fish, 1974). As the rats played, a different and surprising sound sporadically popped up in the headphones – like a chirp. Assuming the sound was another artifact, I swung the bat detector around the room, checking to see if the refrigerator was making more noises, or perhaps something was dripping from the ceiling, or keys were jangling in my pocket. Ruling out those possibilities, I pointed the bat detector back towards the chamber. The rats paused their play. The chirps subsided. Then one of the rats reared up towards me, planting its front paws on the Plexiglas, and twitched. Simultaneously, I heard a chirp.