Perception

• Define sensation

  Physical stimulation of the five senses processed by sense receptors
• Define perception

  Brain interpreting and organising the sensory information
• What is the difference in perception and sensation?

  -Sensation is the detection of stimulus

  -Perception is interpreting what it means
• What are the theories of perception and what are they like?

  -Perception theories differ

  -Gregory sees a difference between sensation and perception.

  -Gibson does not see a difference between the two.

  -Gregory shows an approach with nurture whilst Gibson shows an approach with nature.
• Describe Gibsons theory of perception


  Perception doesn't draw on past experiences, in contrast with Gregorys theory.

  Gibson proposes,

  <There is sufficient information for direct perception

  -Sensation and perception are the same.

  -The eyes detect everything we need, without having to make inferences.

  <Optic flow patterns

  -When moving, things in the distance appear stationary and everything else rushes past.

  -Provides perceptual information about speed and distance

  <Motion parallax

  -A monocular death cue

  -When we are moving past them, closer objects appear to move faster that objects that are further away.

  -Provides perceptual information about speed and distance

  <The influence of nature

  -Perception in inborn,not learned
• Evaluate Gibsons theory of perception

  (+)Real world meaning-Research was on 2nd World War pilots, so relevant to daily life.

  (-)Theory struggles to explain visual illusions-Perception is seen as accurate but illusions trick the brain so theory is incomplete.

  (+)Support for the role of nature-Gibson and Walk showed few infants crawl off a visual cliffs are born with depth perception.
• Describe Gregory's constructivist theory

  Contrasts with Gibsons theory.

  Proposes that sensation and perception are not the same.

  Gregory proposes,

  <Perception as a construction

  -Brain uses incoming information and information we already know to form a hypothesis/guess.

  <Inference

  -Brain fills in the gaps to create a conclusion about what is being seen

  <Visual cues

  -Visual illusions occur because of incorrect conclusions from visual cues

  <Past experience-the role of nurture

  -Perception is learned from experience

  -The more we interact, the more sophisticated our perception
• Evaluate Gregory's constructivist theory

  (+)Support from research in different cultures-People interpret visual cues differently (e.g Hudson's study) showing experience affects perception.

  (-)Visual Illusions-Gregory's research used 2D visual illusions which are artificial ,so theory may not apply to the real world.

  (-)How does perception get going?-Babies have some perceptual abilities, so perception can't be just the result of upbringing.
• What are visual cues?

  visual information from the environment about movement and distance etc.
• What are visual constancies?

  seeing object as the same from different angles and distances.
• What does binocular depth cues use?

  Two eyes
• What do monocular depth cues use?

  One eye
• What are the 2 examples of binocular depth cues?

  1)Retinal disparity

  2)Convergence
• What is retinal disparity?

  -example of binocular depth cue

  -difference between the view of the left and right eye, given brain information about depth and distance.
• What is convergence?


  -example of binocular depth cue

  -eyes point closer together when an object is close.Muscles work harder so know distance and depth.
• What are 4 examples of monocular death cues?

  1)Height in plane

  2)Relative size

  3)Occlusion

  4)Linear perspective
• What is height in a plane?

  -objects higher up appear further away.

  -example of a monocular depth cue
• What is relative size?

  -smaller objects appear further away

  -example of a monocular depth cue
• What is occlusion?


  -if one object obscures part of another object, it is seen as closer.

  -example of a monocular depth cue
• What is linear perspective?

  -parallel lines appear closer as they become more distant.

  -example of a monocular depth cue
• What are the 6 visual illusions?

  1)Ponzo illusion

  2)Muller Lyer illusion

  3)Rubins vase

  4)Ames room

  5)Necker cube

  6)Kanizsa triangle
• Describe the Ponzo illusion

  -Misinterpreted depth cue-converging lines give illusion of distance

  -Perceive horizontal line higher up as longer so we mentally enlarge the top line

  
• Describe the Muller-Lyer illusion

  -Misinterpreted depth cue

  -Two vertical lines the same length

  -Line with outgoing sins seen as longer

  Ingoing fins-shape of outside building, appears closers scaled down.

  Outgoing fins-inside the corner of room, appears further away, so scaled up.

  
• Describe the Rubin's vase

  -Ambiguous figure

  -Face and vase, both pictures correct, brain alternates.

  Two possible interpretation of image.

  Brain can't decide which is correct.

  
• Describe the Ames room

  -Misinterpreted depth cue

  -Room shape of a trapezoid

  -People seen as different sizes even though they are the same

  
• How can we explain size constancy?

  Objects perceived as constant size despite size on retina changing with distance.
• How can we explain misinterpreted depth cues and what are examples of this happening ?

  Objects apparently in the distance scaled up by brain to look normal size, causes visual illusions.

  Ponzo illusion-Converging lines give illusion of distance

  -Mentally enlarge the top line

  Muller Lyer illusion-

  Ingoing fins-shape of outside building, appears closers scaled down.

  Outgoing fins-inside the corner of room, appears further away, so scaled up.
• How can we explain ambiguous figures and what are examples of this happening ?

  -Two possible interpretation of image.

  -Brain can't decide which is correct.

  Necker cube-cube seen as pointing upwards to the right or downwards to the left.
• How was we explain fiction and what are examples of this happening?

  Seeing something that is not there

  Kanizsa triangle-illusory contours, create impression of a second triangle.
• What are the factors affecting perception

  -culture

  -emotion

  -motivation

  -expectation
• How does culture affect perception?

  Social world we live in (culture) affects what our senses pick up.
• How does emotion affect perception?

  The tendency for our brain to notice exciting things and block threatening things.
• How does motivation affect perception?

  Wanting something increase its attractiveness
• How does expectation affect perception?

  Beliefs based on past experiences can affect how much we attend to things
• Describe Hudson's study


  -Aim-to find whether different cultures perceive depth cues in 2D images differently.

  -Method-Showed 2D drawings to black and white children, schooled and unschooled.

  Children were asked which is nearer, the mantle elephant or the antelope?

  -Results-Black and white schooled participants more likely to perceive depth cues, rather than unschooled participants.

  White schooled participants more likely to perceive depth than black schooled participants.

  -Conclusion-Different cultures use depth cues differently, so have different perceptual set
• Evaluate Hudsons study


  (-)Cross-cultural research-language differences could have made method used unclear, so validity is affected.

  (-)Problems with the method-The way the participants were represented on paper may have confused participants, affecting findings.

  (-)Poor design-easy cross cultural studies were poorly designed (no control group), causing findings to lack validity.
• Describe McGinnies study


  -Aim-to know if anxiety provoking things are noticed,more than neutral things.

  -Method-students shown neutral and 'taboo' words.They had to say the word out loud.Emotional arousal measured through the GSR.

  Results-Took longer to say taboo words.Taboo words gave bigger change in GSR.

  Conclusion-Emotion affects perceptual stein this case, perceptual defence.
• Evaluate McGinnies study


  (+)Objective measurement-GSR is a scientific method to measure emotion, better than rating scales.

  (-)Embarrassment not defence-delayed recognition may just be embarrassment not perceptual defence.

  (-)Results are contradictory-difficult to draw conclusions from research that is inconsistent.
• Describe Gilchrist and Nesberg's study


  -Aim-to find out if food deprivation affects the perception of food.

  -Method-Hungry(no food for 20 hours) and not hungry participants, shown a slide of a meal.They and to adjust the light/brightness to level of the slide shown.

  -Results-Perceived food as brighter, the longer deprived of food.

  -Conclusion-Sensitivity greater, when food deprived. Hunger is a motivating factor, that affects perception of food.
• Evaluate Gilchrist and Nesberg's study


  (+)Support from similar studies-Sanford's study found similar results, which strengthens the validity of the conclusions.

  (-)Ethical issues-Depriving people of food causes discomforts case of physical harm.

  (-)Not like everyday life-participants judged pictures rather than real food, so it may not apply to real world.