A border collie once learned over 1,000 words, more than most toddlers

[Rob72]

Genuinely one of my favourite bits of animal science trivia. A border collie named Chaser, trained by retired psychology professor John Pilley in South Carolina over three years, learned the individual names of 1,022 different toys and could reliably fetch the correct one on command, putting her roughly at the vocabulary level of a three year old child. She also understood the concept of exclusion, if asked to fetch something using a word she'd never heard before, she'd correctly grab the one new toy she didn't already have a name for, which is genuinely sophisticated reasoning for any species. The previous record holder was another border collie called Rico who knew about 200 words. Chaser passed away in 2019 at 15, but her research is still cited as one of the clearest demonstrations that dogs can genuinely grasp language structure rather than just responding to tone and repetition.