According to the Institute For Evolutionary Anthropology in Germany, some dogs can recognize up to 200 words, and even figure out what new words mean, making them mentally equivalent to a 3 year old child.
Just like people, animals have two kinds of intelligence: Fluid intelligence, which is their natural smarts like they know instinctively how to hunt or to stay away from the street. Then there's crystallized intelligence, which is how they process everything they've learned like when they put two and two together that when the alarm goes off in the morning, they get fed.
But according to the book "How Dogs Think", you can actually help your pet improve their brain power by teaching them new things that'll increase their crystallized intelligence. Here's how:
A sharp mind also translates into a healthier pet. With nothing to do but sleep and eat, animals get bored and destructive and are more likely to be obese. Keeping their brain busy means your shoes won't be chewed, your cat won't obsessively groom, and your bird won't pluck their feathers out. If you'd like to know more, check out the book "How Dogs Think" by Stanley Coren.