 Aspect-perception and attention. The Necker cube is one of a growing family of alleged counterexamples involving aspect-perception or selective attention. Others include ambiguous pictures such as the famous duck-rabbit; arrays of dots or geometric figures which can be “grouped” by vision in alternate ways; or other displays which can be attended to in multiple ways. In each case, a single and unchanging figure that seems to be univocally represented by vision nonetheless gives rise to differing visual experiences.