Chicken

There are approximately 33 billion chickens alive at any given moment — more than three times the human population. Despite their ubiquity, almost nothing about their inner lives is understood by most people who eat them. Chickens demonstrate object permanence, basic arithmetic, empathy, and dreaming. Their reputation for stupidity is a product of how they're kept, not what they're capable of.

Facts you didn't know

• 1

  Chickens demonstrate object permanence — knowing that an object still exists when they can't see it. This cognitive benchmark, which human infants don't achieve until 7 months old, was long assumed to separate 'intelligent' animals from 'simple' ones.

• 2

  Mother hens communicate with their chicks before they've hatched. During the final days of incubation, mothers cluck to their eggs — and the chicks inside respond with peeps — establishing the specific call-and-response pattern they'll use for the first weeks of life.

• 3

  Chickens experience REM sleep, the phase associated with dreaming, with rapid eye movements and irregular breathing. They also practice unihemispheric sleep — one hemisphere resting while the other stays alert, keeping one eye open to monitor for predators.

• 4

  Mother hens display measurable empathy. When puffs of air were directed at their chicks in studies, mothers showed physiological stress responses — elevated heart rate, changed eye temperature, reduced preening — even when they themselves were unaffected.

• 5

  Chickens understand basic numerical relationships and prefer larger quantities. Day-old chicks track small numbers of objects and consistently choose the larger set — a numerical preference that appears before significant learning can have occurred.