Curious

Flat head, lidless eyes, body dirt brown, the Surinam toad slithers through the pond like animated mud, an amphibian golem. Long fingers filter the swamp floor, sweeping fish and worms into a tongueless mouth. Some romantic gave it the alternate title “star-fingered toad,” because after each foot divides into toes, the toes divide again, creating a “star” at the tip. But celestial the toads are not.

The most disturbing part, though, is the way they breed. Mating, they somersault through the water, the female dropping eggs on the male’s belly when the pair is upside down. Turning, he brushes them onto her back and fertilizes. The eggs sink into her body, leaving pale warty bumps until, months later, fully formed miniature toads (not tadpoles) burst out and swim away. When they’ve gone, her back is all holes like a drained honeycomb.

In the seventeenth century, every collector in Amsterdam coveted a Surinam toad, in a box, in a painting, in a jar. The Dutch had colonized Surinam, a small country on the northeast shoulder of South America. Between planting sugar and pineapple, they marveled at the creations of the tropical rainforest. Frederik Ruysch, botanist and midwifery expert, kept one in his cabinet of curiosity, a gathering of oddities, the precursor to museums, where his friends could come gawk. Nicholaes Witsen, burgomaster and avid collector, reported seeing the disconcerting toad and described it: “all the back is open as a wound.”

Some viewers interpreted the ugly appearance as a judgment for ugly habits: “The pipa is, in form, more hideous than even the common toad; nature seeming to have marked all these strange mannered animals with peculiar deformity,” wrote Oliver Goldsmith in A History of Earth and Animated Nature in 1774.

Those who seek her out today still have a visceral response. Comments on a YouTube video of toadlets tearing the skin and kicking free include “damn nature you scary!” and “as a lover of animals im ashamed to say i said KILL it with fire and dont stop . . kill it burn it kill it burn it! then bury it and shoot the grave!” (A more sober-minded commenter suggested that, compared to watching a human birth, it wasn’t bad at all.)

Given the strength of the recoil, why can’t we look away? The You-Tube video has been watched almost half a million times. Perhaps now you are tempted. Knowledge of South American toad habits has little practical application. What is the nature of the itch we call “curiosity”?

Like the toad, curiosity is a strange beast. The investigating mind moves like a sleek little mammal, a mink maybe, rubbing up against things in the dark, trying to determine their shape, occasionally ripping with sharp teeth and pawing through the opening. Or perhaps a spider, creeping precisely, attaching silk here, and here, and here to impose a pattern where before was just air.

Curiosity can be as obsessive as hunger or lechery, swamping the senses. But it is notoriously fickle, too, slinking away as soon as it is satisfied. Its subjects seem so frivolous: a baby giraffe, a dodo skeleton, the Surinam toad. George Loewenstein, author of “The Psychology of Curiosity,” summed it up: “The theoretical puzzle posed by curiosity is why people are so strongly attracted to information that, by the definition of curiosity, confers no extrinsic benefit.” St. Augustine defined it is as “ocular lust,” the desire to stare at an object, animal, or scene and let the mind roam. Charles Darwin, who you might think would value the trait, saw it as the enemy of substantive inquiry. He wrote in a letter to a friend: “Physiological experiment on animals is justifiable for real investigation, but not for mere damnable and detestable curiosity.”

This kinship to physical passion—the strength of desire, the burst of delight—makes curiosity waver between vice and virtue. Intellectual curiosity sparks science, art, all kinds of innovation. Here, in most of twenty-first-century North America, it is held in the highest esteem. For much of history, though, coveting the secrets of the world and mulling over mushrooms...