Perception

• The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. The brain makes sense out of the input from sensory organs.

• Immanuel Kant (1724-1804) maintained that knowledge comes from our inborn ways of organising sensory experiences. John Locke (1632-1704) argued that we learn to perceive the world through our experiences.

→ Visual Perception:

• Vision is our most important sense, in fact the brain devotes most of its processing to visual processing.

• Typically we think that visual perception is effortless, but information arrives at our retina confused and disorganised. Different colours are present and the retinal shapes and sizes of objects are often very different from their actual shapes and sizes.

• Another complication is that the retinal image is 2-dimensional, but we still perceive the world as well-organised and three-dimensional. The complexities of visual perception can be understood by learning about CAPTCHAs.

• CAPTCHAs are automated tests that can tell computers and humans apart. They require the observer to identify visual stimuli (letters and digits) presented in a distorted form. They’re designed to be easy for humans to solve but difficult for machines. These are used to prevent problems like automatic spamming on Facebook.

→ Perceptual Organisation:

• The visual environment is typically complex and confusing, some objects overlap others and hide parts from our view, and as a consequence it can be hard to achieve perceptual segregation of visual objects.

• The Gestalt psychologists (Koffka, Kohler and Wertheimer) studied perceptual organisation, and their fundamental principle was the Law of Prägnanz.

• The Law of Proximity states that visual elements close to each other tend to be perceived as one group. The Law of Similarity states that similar visual elements tend to be perceived as one group. The Law of Good Continuation  states that visual elements that produce the least interruptions to smoothly curving lines are grouped together. The Law of Closure states that the missing parts of a figure are filled in to complete it. These 4 laws are specific statements of the basic Law of Prägnanz.

• These aforementioned laws are natural to our brain. We learn that visual elements close/similar to each other generally belong to the same object, and even very young infants show grouping by good continuation, proximity and connectedness. Other grouping principles are only used later in life, and thus learning plays an important role in perceptual grouping.

• The Gestaltists argued that the grouping of visual elements occurs ahead of most other visual processes, referring to the figure-ground segregation.

• Figure-ground segregation is when one part of the visual field is identified as the figure (central object), and the rest of the visual field is less important and forms the ground. According to the Gestaltists, figure-ground segregation happens very early in visual processing and always precedes object recognition. It is believed that this depends on past experience and familiarity with the object, and therefore it’s not completely something innate.

→ Depth Perception:

• The core achievement of visual perception is our ability to use the information contained in the 2-dimensional image on the retina to produce 3-dimensional perception.

• Good depth or distance perception is very important, for example, we need to know how far away cars are so that we can cross the road safely.