Among mammals, the relationship between the age at which an animal develops locomotion and the age at which it first begins to play has been widely studied. The table below lists "onset" times for locomotion and for play in eleven different species (46). Fit the data to the y = ax model. Locomotion Play Begins, Species Begins, x (days) y (days) Homo sapiens 360 90 Gorilla gorilla 165 105 Felis catus 21 21 Canis familiaris 23 26 Rattus norvegicus 11 14 Turdus merula 18 28 Macaca mulatta 18 21 Pan troglodytes 150 105 Saimiri sciurens 45 68 Cercocebus alb. 45 75 Tamiasciureus hud. 18 46