People feel comfortable when everything happens as expected. When people around us (people, animals, objects, programs) behave predictably, good relationships form between us. In this context, design elements should look consistent with their behavior. First the function, then the form. In practice, this means that the appearance of an element should speak of how it will behave when interacting. If the element looks like a button, then it should work like a button. No need to tinker with basic interactions … save your creativity for higher-order tasks.