Perception Flashcards
Sensation
- Info from world we receive by our 5 senses
- Environment stimulates our sense receptors
- Info turned into tiny electrical signals in our brain (transduction)
Transduction
Info turned into tiny electrical signals in our brain
Perception
Perception is the process of interpreting sensory information to give it meaning
Monocular depth cues, give examples
A way of detecting depth or distance which will work with just 1eye
* Height in plane
* Relative size
* Occlusion
* Linear Perspective
Binocular depth cues, give examples
A way of detecting depth or distance which requires 2 eyes in order to work
* Convergance
* Retinal Disparity
Mono or Bino
Height in plane
Monocular Depth Cue - things that are further away look higher up
Mono or Bino
Relative Size
Monocular Depth Cue - Things that are closer appear larger
Mono or Bino
Occlusion
Monocular Depth Cue - Involves 1 object overlapping/covering another - when this happens it appears to be that the object that is overlapping the other is closer
Mono or Bino
Linear Perspective
Monocular Depth Cue - Straight lines pointing towards a single point in the horizon (vanishing point), this helps us understand distance in a landscape for example
Mono or Bino
Convergance
Binocular Depth Cue - The closer the object, the more the eye muscles have to move in their sockets. This muscle movement provides the brain with depth info.
Mono or Bino
Retinal Disparity
Binocular Depth Cue - Further away something is, the more similar these 2 images are, the closer the image is the more different the 2 images are as the 2 eyes send different impulses to the brain, so brain receives 2 different images
4 main reasons for visual illusions
- Ambiguity
- Fiction
- Size Constancy
- Misinterpreted depth cues
Misinterpreted depth cues
Wrongly applying the ‘rules’ of depth perception (high, low, shallow, deep)
Ambiguity
When an image could equally well be one thing or another
Fiction
Ccreating something that isnt really there, to complete an image
Size Constancy
The tendency to perceive an object as being the same size regardless of whether it is close or far away
The Ponzo Illusion
- Misenterpreted depth cues
- Relies on depth cues of linear perspective with the other 2 outer lines of the drawing creating an illusion of perspective
The Muller Lyer Illusion
- Misenterpreted depth cues
- Lengths look different as arrows point in different directions, in fact, the lines are the same length
Rubin’s Vase Illusion
- Ambiguity
- We see both 2 faces and a base
The Ames Room
- Size Constancy
- Looks like an ordinary room from front but is distorted which makes 2 people in opposite corners look larger/smaller than each other
The Kanizsa Triangle
- Fiction
- We perceive a triangle because we mentally connect objects that appear to belong together
The Necker Cube
- Ambiguity
- Brain cannot decide where the front is, can be seen in different views
Gibon’s Theory
- Direct Theory of Perception
- Perception happens without using expectations and past experience
- Perception happens directly, due to the info provided by our environment
Gregory’s Theory
- Constructivist Theory of Perception
- Perception is dependant on past experience and knowledge
Bottom-up processing
- When you interpret information that is unfamiliar by examining the information
- Take place in real time
- Relies on sensory info
Top-down processing
- We use contextual information, expectations, experience, schemas
e.g h_me, we know it’s o because of past experience and the letters around it
Explain Gibson’s theory
- Our perception only requires info from environment (motion parallax)
- We don’t need to make inferences
- Our perception of objects includes possible uses for that object (affordances)
- Some perceptual abilities are innate (from birth)
Motion Parallax
The way in which our visual field changes with movement with close objects seeming to move more than objects that are far away
What is gradient of texture and how does it help us to judge distance?
- The texture appears smoother and finer as the surface is far away
What is gradient of colour and how does it help us to judge distance?
- Colours look brighter when closer
- Colours look paler when further away
What was Gibson’s evidence? What does it show?
- Visual Cliff Experiment
- A baby would not fall of the cliff becasue they have perceptual abilities as they were able to detect danger/high drop, suggests that depth perception is due to nature
Arguments to support Gibson’s theory
- Perceptual abilities (like perceiving depth) might be due to nature (innate) & we dont need past experiences to perceive the world
- Evidence from infant research suggests that depth perception might be innate/inborn because:
1. we are always moving
2. we never perceive things from a static view
Arguments against Gibson’s theory
- Research into visual illusions show that sensation and perception are 2 different processes but Gibson argues that they are the same. There is evidence to disprove this
- This undermies Gibson’s theory as not everything we perceive is direct, we need to make inferences by using past experiences.
Explain Gregory’s theory
- Past knowledge is the most important thing in making sense of what is around us
- Perception works because our brain makes reasonable guesses about what we see on the basis of what it is most likely to be - perceptual hypotheses
- Visual illusions provide evidence to support this theory
- Perception gets more sophisticated as we get older
- Stored knowledge and expectations come from past knowledge
- Perception is creating uing both sensations and stored knowledge
Gregory’s theory - explain stimulus
- Stimulus is vague so we require higher cognitive info either from past experiences/stored knowledge to make inferences
- A lot of info lost from eye –> brain (90% lost)
- We actively construct our perception of reality
What kind of processing is Gregory and Gibson’s theories?
Gregory = Top- Down
Gibson - Bottom -Up
Arguements to support Gregory’s Theory
- Schemas, past experiences, interpretations we make of the sensations we receive are affected by past exp
- Nurture has an effect on perception - participants were affected by their expectations or how they were feeling at the time of the study
- Bruner And Minturn’s study support it - showed importantce of human experience
Nature or Nurture, which theory fits each?
Gibson = Nature
Nurture = Gregory
Arguements against Gregory’s theory
- Supported by unusual examples of perception such as uncertain or ambiguous information like in visual illusions. Gregory’s theory can explain artificial 2D images but these might not tell us much about how perception works in the real world.
Factors that affect perception
- Culture
- Motivation
- Emotion
- Expectation
How does culture affect perception?
- Culture: ideas, norms, social behaviour (that surrounds you)
- e.g Western culture draws animal from side view, African tribal society draw it spread out
How does motivation affect perception?
- We have many motives e.g physcial motives like hunger, this encourages us to eat/ drink
How does emotion affect perception?
- Our emotions can make us perceive things in life based on how we feel
How does expectation affect perception?
Bruner and Minturns study shows how expectations can influence how we interpret what we see
Gilchrist and Nesburg “Need and Perceptual Change” Study (1952)
AIM
- Aim - Investigate how motivation affects perception
Method of Gilchrist and Nesburg Study
- 26 uni students - 1 group deprived of food for 20 hrs, other group ate meals normally
- All shows slides of food for 15 seconds each
- After each slide was shows, participants were asked to adjust lighting on a new photo so it looked like the original
- They were tested at start of study, after 6 hours and after 20 hours
Results of Gilchrist and Nesberg’s Study
- Control group (not hungry) showed little difference
- Experimental group (hungry) judged the pictures to be brighter as they got hungrier
Conclusion of Gilchrist and Nesburg
Hunger can affect the way we perceive images of food, which suggests that motivation affects perception
Positives of Gilchrist and Nebsurg’s study
- High exological validity - participants were actually hungry - can happen irl
- Study was highly controlled (lab exp), same conditions for both groups except hunger
- Makes it easier to replicate - increases reliability of results and conclusion drawn
Negativs of Gilchrist and Nebsurg’s Study
- There could have been other factors that can affect their motivation
- Ethical issue - may have caused participants some discomfort and distress, they may have not understoof how difficult it would be, not fair and justified for science
Perceptual Set
A state of readiness to perceive certain kinds of stimuli rather than others
Bruner and Minturn’s Perceptual Set Study - Aim
To investigate how expectations can direct perception
Bruner and Minturn’s Perceptual Set Study - Method
- 24 people looking at recognising numbers and letters
- Letters/numbers flashed very quickly
- They were asked to draw letter/number as soon as they could recognise it
- 1/2 people shown 4 stimulus letter then “B”
- Then series of letters then “B”
- Then series of letters and numbers then “B” X3
- Other half had same procedure, it was counterbalanced
Bruner and Minturn’s Perceptual Set Study - Results
- Most drew open figure like 13 when expecting a number to come up
- Most drew a B when expecting a letter to come up
- When expecting either, there were mixed results
Bruner and Minturn’s Perceptual Set Study - Positives
- Synoptic link: Has real life application e.g Bartlett War of Ghosts explains why participants changed the story based on their expectations - Strength as we see it happening in real life - increases credibility of theory
- Study was carefully controlled & counterbalances - can be replicated - increases reliability in findings
Bruner and Minturn’s Perceptual Set Study - Negatives
- Doesn’t consider participants individual differences, lucky number could be 13 or fam/friends could start with a letter B
- Lacks ecological validity - isn’t similar to perception in real life, we are rarely faced with ambiguous figures
