Invariances and Experimental Phenomenology: an introduction

The idea that the brain of the neonate begins as a “tabula rasa”, and that the complex precepts of the adult can be traced back to a history of learned associations made from the time of brith, originated in empiricism, sets the foundational ground to modern neural network or connectionist theories, whereby individual sensations are related to the activation of individual neurons, or neuron assemblies in the brain expressed by Hebbian learning.

It is, however, hard to understand why we do not see the world as na assembly of dots

Seurat's painting The Circus

but as extended areas and volumetric bodies. Wolfgang Metzger (1936), identifies this problem, and develops a careful description and unbiased analysis of the phenomenological properties of visual perception. In his view, although there seems to be some sort of influence of experience on vision, the organization of the visual field occurs essentially without our involvement.  It is, in fact, not to up to us to decide what and how we see. Rather, we already find the visual world ready-made before us: stimuli organize themselves in the simplest, most symmetrical, and balanced manner. Perceptual constancies (or invariances) is what warrantees that the same object in our environment changes little in perception even when physical conditions under which the stimuli occur vary: Perceptual constancies or invariances are the focus os experimental phenomenological analysis, which has fruitfully developed the Gestalt laws (see also the post on Gestalt and Qualitative Relations). 


The world we see is not the world itself. Metzger, in his Laws of Seeing (1936),  justifies such claims with three major observations:

1. There are percepts for which there is no direct correlate in the physical stimulus. Examples are brightness enhancement and illusory contours

 

1. Certain things are not seen though they are clearly before our eyes. Examples of this are objects that by their proximity and structure become part of an edge or become embedded in larger configurations (hidden objects). 

 

1. We see objects, but differently from the way they are. Some examples are made from stimulus conditions (microgenesis) as well as many geometric-optical illusions, where we misperceive shapes, sizes, and angles of stimuli. These observations are undeniable, they cannot be overridden by better knowledge of the actual stimulus, and they have  reality of their own.

As Metzger remarkably explains (1936, xv),

On a more recent account of this problem, I present the methodological issue on the post Special issue Quantitative Approaches in Gestalt Perception, a review).


References
Metzger, W. (1936). Gesetze des Sehens. 2., erw. Aufl. Frankfurt a. M.: Kramer.

Metzger, W. (2006) Laws of Seeing. Cambridge Mass: MIT Press (original work, 1936).
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