Introduction to Perception Flashcards
what is sensation
a passive process bringing information from the outside world into the body and brain
what is perception
an active process selecting, organising and interpreting the information brought to the brain by the senses
sensory organs absorb…
energy from physical stimuli in environment
sensory receptors convert this energy into…
neural impulses and send to brain
what does the brain do with the neural impulses sent to it from sensory receptors
organises information and translates it into something meaningful
describe the visual cliff experiment and what do the results suggest
Gibson & Walk (1960). infants placed on shallow size of table and encouraged to crawl over ‘visual cliff. 27/36 didn’t cross, suggesting that when healthy infants are able to crawl, they can perceive depth
describe the visual cliff experiment with the importance of experience
Campos et al. (1981). infants with 11 days crawling experience tested in visual cliff task abut half crossed the deep size. 41 days less than a quarter crossed the deep side
why do we study perception
to understand the world around us (survival). to design our environment effectively. to understand features of clinical disorders. curiosity.
what are physical stimuli reduced to
electrical and chemical events
in what way can perception not guarantee accurate representation of the physical world - what can alter it?
experience (visual illusions). brain damage (prosopagnosia). atypical development (sensory deprivation, ASD, DCD)
give an example of perception being context specific
the ebbinghaus effect (orange dots being the same size but looking different sizes due to the size of the grey dots around them)
give an example of the visual system not being passive
Kanizsa’s illusory square. it automatically extends line segments into parts of the drawing where they are missing. mind imagines that an object has been placed over the abstract shapes and lines in the drawing
what does the perception of countless figures reflect?
properties of the way the visual system is wired
what is the fundamental distinction in perceptual processing?
whether we achieve an understanding of the world through bottom up or top down processes
what is top-down processing?
identification of objects using existing knowledge to guide processing of the sensory information
what is bottom-up processing?
a representation of the object in view is gradually built up from visual image taken in by retina in the eye
how does bottom-up processing work?
implicit or innate processes.
how does top-down processing work?
knowledge, thoughts or expectations influence perception
is bottom-up processing unique?
no - should be generic across species.
is top-down processing unique?
yes - specific to the individual.
what is bottom-up processing shaped by?
evolution
what is top-down processing shaped by?
experience
examples of same length lines looking different lengths
Muller-Lyer illusion (arrows) and Ponzo illusion (train tracks)
perceiving one figure prevents you from…
perceiving the other
to interpret a complex image, the brain has to identify…
a main figure, and relegate the rets of the image to the background
describe the constructivist theory
Gregory (1970). top down there, construction of our world from past experiences alongside real-time visual info. info is lost by the time it reaches the brain. actively construct our perception of reality, the formulation of incorrect hypothesis lead to errors of perception
describe the Gestalt theory
bottom up theory, starting from aspects of visual stimuli that influence perception and work its way up to higher-order cognitive processes. percepts determined by interaction of rules describing organisation. simplest interpretation favoured. whole is more than sum of its parts.
what are the 5 other ‘Laws’ of Gestalt theory
proximity, similarity, closure, continuity, pragnanz
describe the law of proximity
objects near to each other tend to be grouped together
describe the law of similarity
items that are similar tend to be grouped together
describe the law of closure
objects grouped together are seen as a whole
describe the law of continuity
liens are seen as following the smoothest path
describe the law of pragnanz
reality is organised or reduced to the simplest form possible
describe the computational theory
Marr (1982). describes stages of processing required for a computer to see natural scenes. bottom up - views the initial retinal image as starting point of perception. how the brain turns info into accurate internal representations of our surrounding world.
what is grey level description (computational theory)
intensity of light is measured at each point in retinal image
what is primal sketch (computational theory)
raw sketch, areas potentially corresponding to edges and textures OR full sketch, these areas used to generate description of outline any objects in view
what is 2D sketch (computational theory)
description is formed of how surfaces in view relate to one another and to the observer
what is 3D object centred description (computational theory)
object descriptions produced allowing object to be recognised from any angle
