“Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world.” Albert Einstein

Difference between seeing and perceiving Close your eyes and press on your eyelids What do you see?

Draw the images below

What is Perception? Perception is many things to us. It is the here and now of our lives--the moment to moment awareness of our environment. It is the present, from which memories of the past and thoughts of the future are created by the brain. It is our reality. It is what happens to stimuli from the environment after they have been translated into electro-chemical impulses within the brain.

It is how these impulses are organized by the brain to give us the best chance of recognizing stimuli.

Why researchers love ambiguous and impossible figures They provide information on the processes that allow our brains to extract form from indeterminate retinal stimuli The visual system must routinely resolve ambiguity for successful adaptation of organism to its environment They uncouple perceiving and seeing, since you get percept changes (i.e. you ‘see’ something different) without any stimulus change

Types of Visual Illusions Physiological : the effects on the eyes and brain of excessive stimulation of a specific type (brightness, tilt, color, movement) Cognitive illusions: where the eye and brain make unconscious inferences

The perceptual process involves brain structuring, and how it organizes incoming stimuli, determines what we experience. The figure doesn’t change. What we are experiencing is the perceptual process--brain reorganization: the brain finds different ways structuring the stimuli, we experience different images.

Necker Cube

Necker cube (with depth cues)

BACKGROUND – All brain operations involve pattern analysis and model making – Energy conservation: a basic principle – Preference for stability over accuracy – Bias built into system

Why the brain works this way? (i.e. evolutionary advantages) Energy conservation theory Neural lag theory (Changizi)

Neural lag theory When light hits the retina, about one-tenth of a second goes by before the brain translates the signal into a visual perception of the world. the human visual system has evolved to compensate for neural delays, generating images of what will occur one-tenth of a second into the future. This foresight enables human to react to events in present.

To make sense of the world it is necessary to organize incoming sensations into information which is meaningful. The brain create as "whole" image from individual elements. ‘Expectation’ conditions the brain. A preconceived notion can strongly influence what becomes known

The brain extracts the features of a pattern from the information that it senses. In the case of visual images, the lines, curves, contrasts of light and dark and motion are the features extracted The brain reconstructs pattern information into a model.

Grouping and sorting in categories is a natural strength of the brain However, with the ability to group and categorize comes the tendency toward being mistaken because of bias and prejudice

The brain is biologically organized to process information through the construction of internal models. It searches and finds patterns in what it senses. It extracts the features of patterns from the data and assembles those features into a model of the perceived object.

The brain is performing pattern feature- extraction and building models all the time, even if we are not aware or conscious of this process.

The human brain has limited energy availability (13-20 watts), and thus, like all biological systems, it seeks to do its work with minimum potential energy ; therefore the brain has evolved ‘short cuts’ for processing information

The goal is to achieve a stable percept/image/model with least amount of energy; so in exchange for possible loss of information, information processing is greatly speeded.

we often ignore or misinterpret contradictory data that might cause us to become less certain, in order to avoid the ambiguous (energy demanding) state.

Bias and tenacious adherence to the status quo are intrinsic to the system. The circuitry of the brain prefers stability to accuracy. In the case of ambiguous information, it will do this by either ignoring some information or by increasing bias to lock onto a stable model.