Aggressive "spiky" buttons against rounded

At the UX Australia 2009 conference, Keith Lang talked about how the geometric shape of the interface elements is perceived differently by humans. For example, rounded rectangles look naturally friendly, and some other shapes - hard and unpleasant. However, they can be used. Keith gave a very interesting example of how you can benefit from the use of aggressive "thorny" buttons.

In this picture both buttons are equally round and sweet.


')
And then the delete button is "toothy."



In the second case, think twice before you press the button, ready to bite off your finger.