![](https://www.koko.org/wp-content/uploads/2010/03/pj_2005_06_03.sleep_.jpg)
Koko signs "SLEEP"
Penny & Darlene sign "SLEEP"
GSL (Gorilla Sign Language: Modified ASL + Natural Gestures)
ASL (American Sign Language)
Koko signs "SLEEP"
Penny & Darlene sign "SLEEP"
GSL (Gorilla Sign Language: Modified ASL + Natural Gestures)
ASL (American Sign Language)
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