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CU shot of baby birds in nest with mouths wide open. MS of parent birds in tree branch feeding babies. Several other shots of this occurrence. Shot of fledglings in nesting in a lab. Cross fade to man leaning into them, making caw sound. Reflexively birds lift up heads and open mouths. Cut to shot of dog strapped to table, puppy placed under it by girl. CU of puppy on table. Narrator talks about puppy given nothing but bread and milk for nine months. Fade to puppy grown up on table, girl tries to offer him meat, he turns it down and is indifferent. Shot of puppy taking bite. Narrator says from that moment meat is the strongest possible stimulus. Shot of dog licking lips.