A non-profit since 1979, Helping Hands used to teach monkeys to play these 12-inch objects; now they play CDs instead
Megan explained 
that Helping Hands staff and volunteers train monkeys to perform a ... tasks, such 
as putting a CD in a CD player, scratching their partner's nose,... [DOC] [TLE] Activity: Perspective | Leonardo Da Vinci - The Genius [PAR] People and objects look larger when they are nearby and smaller when they are 
... use a simple set up to measure the change in the apparent size of an object as 
it ... or box 10-12 inches tall, a tape measure, an easy to read ruler with quarter 
inch ...