Stimulus ambiguity

Stimulus ambiguity is an aspect of stimulation and occurs where aspects of a stimulus can be open to interpretation. For example when we view in an ambiguous image our perception may move from one interpretation of the object to the other. But these issues run deeper as theses historical discussions show.

Empirical accounts of vision
Visual perception is initiated when objects in the world reflect light rays towards the eye. Most empirical theories of visual perception begin with the observation that stimulation of the retina is fundamentally ambiguous. In empirical accounts, the most commonly proposed mechanism for circumventing this ambiguity is "unconscious inference," a term that dates back to Helmholtz.

According to Hatfield, Alhazen was the first to propose that higher-level cognitive processes ("judgments") could supplement sense perception to lead to veridical perception of distance, suggesting that these "judgments" are formally equivalent to syllogisms. Descartes extended and refined this account. Berkeley departed from this tradition, putting forth the new idea that sensory systems, rather than performing logical operations on stimuli to reach veridical conclusions (i.e. these light rays come with certain orientations relative to each other, therefore their source is at a certain distance), make associations, so that for instance if certain co-occurring sensory attributes are usually present when an object is at a given distance we see an object with those attributes as being at that distance. For Helmholtz Berkeleyan associations form the premises for inductive "judgements," in Alhazen's sense of the term. Helmholtz was one of the first thinkers on the subject to augment his reasoning with detailed knowledge of the anatomy of sensory mechanisms.

In hiswork Helmholtz's use of the term is construed as referring to some mechanism that augments sense impressions with acquired knowledge or through application of heuristics. In general, contemporary empirical theories of perception seek to describe and/or explain the physiological underpinnings of this "unconscious inference," particularly in terms of how sensory systems acquire information about general statistical features of their environments (see natural scene statistics) and apply this information to sensory data in order to shape perception. A recurring theme in these theories is that stimulus ambiguity is rectified by a priori knowledge about the natural world.