Dogs have the amazing ability to memorize hundreds of words, like Rico, mentioned above, and Chaser, the Border Collie, who learned over 1,000 words.
They are good at remembering faces and always recognize the face of their family member. They also think about games, about food, but still their main thoughts are devoted to the person and their flock. They experience the full range of "natural emotions": fear, pain, joy, affection, boredom, love.
Many dog owners claim that their pets distinguish between intonations, understand human speech, and even sometimes “respond” to some words and phrases. A number of studies confirm that dogs have excellent hearing combined with an unmistakable ability to analyze and process various speech sounds.
Dogs understand and respond to an average of 89 words and phrases. At the same time, the most trained of animals can understand up to 200.
A major study is underway at the University of California San Diego trying to determine if buttons can allow dogs to communicate meaningfully.
In many cases, if a pet's tail deviates more to the right than to the left when he wags it, this indicates that he is in a happy state. If he wags his tail in this way when interacting with a person, it also indicates a strong affection. This is one of the many signals that dogs give with their tails.