The Dog Who Knew 59 Toys Whisky was a border collie in Norway. Her owner never formally trained her. She just learned toy names by listening. Scientists at Eötvös Loránd University tested her. She correctly fetched 59 different toys by name. She could even sort them by shape. All self-taught.
Source
https://www.burgesspetcare.com/blog/dogs/is-your-dog-a-genius/Spot an error? Email hello@thefact5.com with a source — we correct visibly.