My daughter, age 6, sleeps with her bear, also age 6. My son, age 3, sleeps with his basketball and a stuffed tiger, age unknown. My other son, also age 3, sleeps with a can of anchovy fillets--King Oscar brand, caught off Morocco and distributed by the H.J. Nosaki Company in New York.

He sleeps with the can every night, won't go to sleep without it under his right cheek. The can is bright red and features a drawing of King Oscar, an avuncular, bearded fellow, apparently a benevolent despot. Every night, after Liam is asleep, I gently delete the can from his grip and examine it. It's a roll-key can, 56 grams, with 'about six fillets (15 g).' Other than the friendly visage of King Oscar, my favorite thing about the can is the word about, a rare corporate concession to ambiguity. I suppose it's a legal thing, but still it pleases me, for murky reasons.

I sit there in the dark, holding the anchovies, and ponder other murky things, like: What's the deal with this boy and his anchovies? How is it that we are drawn to the odd things we love? How did anchovies from Morocco come to be swimming headless under my son's cheek in Oregon? What do we know about anchovies other than their savory saltiness? What do we really know well about any creature, including most of all ourselves, and how is it that even though we know painfully little about anything, we often manage world-wrenching hubris about our wisdom?

Consider the six animals in the can. Anchovies are members of the family Engraulidae, which range in size from a Brazilian anchovy the size of your thumbnail to a ravenous New Guinea anchovy as long as your forearm. Anchovies don't survive in captivity, and they don't survive long after being netted, either, so we know little about them--but the little we know is riveting:

--Their hearing is perhaps the sharpest of any marine animal's, and the frequency they hear best is eerily, exactly the frequency of the tailbeats of other fish. Is it with the aid of their unimaginably crisp hearing that they manage to swim in darting collectives that twist as one astonishing creature? We don't know.