| A | B |
| proximate causation | how a behavior happens |
| ultimate causation | why a behavior happens |
| habituation | reduced response to stimuli |
| imprinting | early social attachment |
| altruism | behavior that benefits other at expense of self |
| classical conditioning | learning based on 2 kinds of stimuli |
| operant conditioning | learning uses positive and negative reinforcement |
| intersexual selection | selection between different sexes |
| intrasexual selection | competition between same sex for mate |