Do animals dream? Some researchers are convinced they do.

After scouring years of research on sleeping animals, they’ve found three categories of evidence. First, in numerous species, the brain’s electrical activity during sleep intermittently mimics that of their awake activities, such as zebra finches singing.

There’s behavioral evidence too. Many chimps taught American Sign Language periodically sign in their sleep.

The anatomic evidence may be the most compelling. There’s a part of the brain that keeps us from literally acting out our dreams. Cats missing that site leap up while asleep and physically perform their dream sequences.

Our dreams have been touted as proof that humans are superior to animals — but maybe that dividing line isn’t so distinct after all.