A mental image exists in an individual's mind, as something one remembers or imagines. The subject of an image need not be real; it may be an abstract concept, such as a graph, function, or imaginary entity. For example, Sigmund Freud claimed to have dreamed purely in aural-images of dialogs. Different scholars of psychoanalysis as well as the social sciences such as Slavoj Žižek and Jan Berger have pointed out the possibility of manipulating mental images for ideological purposes. Images perpetuated in public education, media as well as popular culture have a profound impact on the formation of such mental images:"What makes them so powerful is that they circumvent the faculties of the conscious mind but, instead, directly target the subconscious and affective, thus evading direct inquiry through contemplative reasoning. By doing so such axiomatic images tell us what we shall desire (liberalism, in a snapshot: the crunchy honey-flavored cereals and the freshly-pressed orange juice in the back of a suburban one-family home) and from what we shall obstain (communism, in a snapshot: lifeless crowds of men and machinery marching towards certain perdition accompanied by the tunes of Soviet Russian songs). What makes those images so powerful is that it is only of relative minor relevance for the stabilization of such images whether they actually capture and correspond with the multiple layers of reality, or not." - David Leupold, sociologistThe development of synthetic acoustic technologies and the creation of sound art have led to a consideration of the possibilities of a sound-image made up of irreducible phonic substance beyond linguistic or musicological analysis.