For example, you may learn that normal aged subjects have difficulty learning new motor skills, but that verbal learning is not influenced by age. You conclude that old dogs can't learn some new tricks, but that other new tricks are no problem. Plagiarism is an act of academic dishonesty. Birds of a feather flock together. Violent pornography is an outlet for sexual aggression.
Boys are better at math than girls.
Girls are less aggressive than boys. Women are more empathetic than men. Out of sight, out of mind. If you can't beat 'em, join 'em. List the variables.