PSYCHOLOGY!! Which is an example of an ulterior motive? Johan found a great Web radio site and shared the URL with his co-worker Sandi simply because he thought she'd enjoy it.
Brian notices Marco forgot his lunch, so Brian gives half of his sandwich to him with no expectations.
Becky went on a date with Rick because she hoped she'd get a free meal.
Jerome noticed some litter and placed it in the trash. Nobody saw and no one said thanks.