This video contains footage from 1972, when Koko was 1 year old and Penny had recently started teaching her sign language. The signs Penny (and her advisor Dr. Karl Pribram) decided to start with were Eat, Drink and More. These signs were decidedly important to infants and would be frequently repeated. Koko picked up the signs quickly, likely due the predisposition of gorillas (and all apes) for gestural language. Koko would go on to learn over 1000 signs and understand spoken English!