Did Alex the parrot and Koko the gorilla really use language?

Not in the full human sense, by most scientific accounts, though both animals clearly learned to communicate. Alex named objects, colours and quantities, and Koko used many signs adapted from American Sign Language. But the scientific consensus is that Koko did not show the syntax or grammar required for true language, and Alex's own trainer never claimed more than a two-way communications code.

Alex was a grey parrot and the subject of a thirty-year experiment by the animal psychologist Irene Pepperberg. His training used a model/rival technique: he watched two trainers interact, one modelling the desired behaviour and acting as a rival for the other trainer's attention. In 1999 Pepperberg reported that he could identify 50 objects, recognise quantities up to six, distinguish seven colours and five shapes, and understand 'bigger', 'smaller', 'same' and 'different'. Looking at a mirror, he said "What color?" and learned the word "grey" after being told it six times. In research testing he gave the correct answer about 80 percent of the time.

Koko, a gorilla, used many signs adapted from American Sign Language and understood nouns, verbs and adjectives. Some experts said she used language in the same way as people. Others, notably Herbert Terrace and Laura-Ann Petitto, suggested she was simply being prompted by her trainers' unconscious cues to display specific signs.

Critics acknowledged that Koko learned a number of signs and used them to communicate her wants, but that did not mean she spoke sign language, which requires syntax and grammatical sentences. Terrace, for his part, thinks Alex performed by rote.