PSYC1001_Lecture 3 Perception Part 1_2024_1pp.pdf

Foundations of Psychology Perception Part I CRICOS Provider Code 00301J  COMMONWEALTH OF AUSTRALIA Copyright Regulation 1969...

Foundations of Psychology Perception Part I CRICOS Provider Code 00301J  COMMONWEALTH OF AUSTRALIA Copyright Regulation 1969 WARNING This material has been copied and communicated to you by or on behalf of Curtin University of Technology pursuant to Part VB of the Copyright Act 1968 (the Act) The material in this communication may be subject to copyright under the Act. Any further copying or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice CRICOS Provider Code 00301J  Acknowledgement of country CRICOS Provider Code 00301J  Lecture Outline Sensation vs perception Perceptual processes  Bottom-up vs top-down processing Signal Detection Theory pathway to understanding why people might percieve the world differently and how might that influence their behaviour CRICOS Provider Code 00301J  Think about it… Is sensing a stimulus the same as perceiving it? automatic For example, is seeing simply absorbing light?  Why/why not? sense things without percieving them; we are not consciously aware of it so we are not percieving it Do we perceive things as they “really are”? sensation: comes into our eyes, ears image was the same, but what people thought of their image (their perception) is different CRICOS Provider Code 00301J  What is sensation? Senses are… “A system that translates information from outside the nervous system into neural activity” transduces physical energy into neural message Bernstein et al. (2012, p. 109) Which means that sensation is… “The detection of physical energy by the sense organs, which then send information to the brain” Lilienfeld et al. (2012, p. 114) So, sensation is the starting point for perception, but not what we’re covering in this unit CRICOS Provider Code 00301J  What is Perception? Perception is how we know anything about our world  No conscious experience without perception  “Your world is what your senses tell you” (Coren et al., 2003, p. 4) you can sense things without being consciously aware of it Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Do we see things as they really are? muller lyer illusion Which line is longer? Naïve realism = the idea that we perceive an objective truth, the “real world” the idea that perception is simple Perception is actually a very complex process of converting sensations to something meaningful Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Is perception outside our control? its the same length but it looks longer (muller lyer illusion) It’s hard to un-see it… whats out there is what our mind percieves; perception is often complex and dynamic in the outer world Image taken from Howe & Purves (2005); https://doi.org/10.1073/pnas.0409314102 CRICOS Provider Code 00301J  Is perception outside our control? differe nt modules in our mind that are set Feature detectors in our brain to percieve certain things (neurons) that recognises and percieves different stuff Processing of basic visual muller lyer illusion works really well visual processing elements is automatic and regrdless of whether you knw the thoery or “simple” lines; edges not  Not really amenable to conscious interpretation  “Modules” separate from other processes  E.g. single neurons in visual cortex respond to vertical or horizontal lines, or edges So sometimes perception appears Image from https://www.ophthalmologytraining.com/ to occur without our influence. BUT... Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  visual system to detect simple features; compklex in reality \, and need to understand the whole picture (are there any pictures that look like an eye) top down: apply your knowledge and other influences that shapes your perception (seeing the cow has shaped your perception to view a cow in this picture) Coren et al. (2003) CRICOS Provider Code 00301J (Coren, et al., 2003)  Coren et al. (2003) CRICOS Provider Code 00301J (Coren, et al., 2003)  So, what happened there? Sometimes our perception can be influenced or directed perception is a lot more involved; and comprises opf internal processing  Particularly complex or ambiguous stimuli So – there must be more than 1 type of process involved in the way we perceive our world  Some perceptions are quick and automatic looking at a line  Some perceptions can be guided  Perception is more complex than just taking in (sensing) external information. Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Perception - Definition “The brain’s interpretation of raw sensory input” sensory input is nothing withiut perception not processing of Lilienfeld et al. (2012, p. 114) sensory input “The process through which people take raw sensations from the environment and interpret them, using knowledge, experience, and understanding of the world, so that sensations become meaningful experiences” Bernstein et al. (2012, p. 157) Involves cognitive processes, memory > interpretation  Not necessarily deliberate/conscious and behaving; how i should behave towards a piece of  Active and complex process cake with grey flyuff; im not going to eat it now Interpretation provides behavioural cues; “Perception provides us with the necessary information to behave appropriately” (Goldstein, 2014) CRICOS Provider Code 00301J  Studying Perception How do we recognise objects? How do we organise our perceptual world? E.g. how do we classify objects? categorising How do we recognise faces? How do we judge distance? How do we tell where a sound originated? … we make mistakes in our i.e. – how we form conscious representations of our perception environment, and how accurate they are Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Why Study Perception (e.g., vision)? Practical applications 1970; plane crash caused visual illusion and misjudge the distance where they had to land and the slope of the city Awareness of perceptual failures can enhance help us work out how and why peop.e make  behaviour towards a particular stimulus can help advertising; camera mistakes safety – e.g., pilots editing make pencils look sharp and big; manipulated to change peoples perception of it to buy it more; misrepresentation of product 1  Practical applications getting people to view a certain car model as more safer The study of perception can tell us a lot about how the mind works  Specific processes for specific types of information, or modularity – different cognitive modules (and brain areas) for different types of modularity information processing around the explains why someone shows a perceptua; particular symptom system  Distributed processing – multiple brain areas involved if partuclar ragion of brain is damaged and therefore cant percieve a particular aspect of a thing Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J CRICOS Provider Code 00301J  Why Study Perception (e.g., vision)? Modules – fast, automatic and process without interference (similar in most people) Learned or genetic? Implicit in psychological theories unique feature detectors: kitten movement of experiements in a room half and half spiraling and one room only had horizontal line \s perxeption taht black and white speace \\, the other they intersect, kittens had verticallines when in reality if your aise the kittens with horizontal they dont lines only, they could only see the horizontal lines and hey couldnt pic up the vertical lines (couldnt see chair legs but could jump across) and this was emphasises the vice versa for the kittens raised up in neurons picking vertical lines up edges vs does evolution not innate aspect of neurons that pick perception? and how do we learn this? up colours; how a lot of things in perception that we still we cant stop need to figure out ourselves from doing it Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Perceptual Illusions Important tools, because they inform us how our perceptual system works evolutionary advatage  Seems to a universal experience  But learning/experience is also important Occur in daily life, e.g.  Perceivingvertical lines as longer than horizontal  The Parthenon – built to seem square, but isn’t Important to know when our perceptions are likely to be distorted  Often, we don’t realise… Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  when we look up we tend to see things as spread out, and if the columnns\ buiding was used to counteract the visual ilklusions that we have and gives us the experience of perfectly straight lines CRICOS Provider Code 00301J  Bottom-up processing CRICOS Provider Code 00301J  Bottom-Up/Ecological/Direct Perception top down and bottom up: two main aspects of perceoption no additional Perception is direct - relies solely on incoming sensations. information to make sense of the world  Brain processes only the sensory information it actually receives and directly converts this into perceptions build up interpretagtion of the world with building blocks that Perceiving “what is out there” construct a unique perception   Start with small details, build up to overall perception Higher-level cognitive analysis not needed  Whole stimulus perceived based on its parts Perception then informs cognition Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  A Visual Processing Example According to bottom-up processing:  Light enters the eye  Signals are transduced – from light energy to neural signal  Automatically processed in one direction (from eye to brain)  Certain neural cells fire only in response to certain visual features (e.g., horizontal lines, diagonal lines, colour, motion, shape) complex visual receptors that  Feature detectors (specialised cells) pick up and reconstruct this  Brain damage can impair specific perceptual ability (e.g., colour)  Hierarchical and parallel:  Basic features of stimulus analysed and then combined into increasingly complex perception (hierarchical) processed stimuli gets at the same time  Perception is built through layers of analysis (parallel processing) o E.g., “box detector” from a combination of several line detectors o Information is combined from different brain areas srtart with simple bits and eventually Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) construct the complex bit CRICOS Provider Code 00301J  Visual agnosia some features are recogised through visual processing/ A-gnosia = “not knowing” interpretation the whole thing is not recognised Apperceptive visual agnosia: an abnormality in visual perception and discriminative process, despite the absence of elementary visual deficits. you can see parts of it but some tings he cant see the whole things  These people are unable to recognize objects, draw, or copy a figure.  They cannot perceive correct forms of the object, although knowledge of the object is intact.  It is typically associated with lesions to the parietal, occipital cortex. Some features can be recognised, e.g. shape, colour, but unable to combine them into a complete perception of the object both structural part which processes faces is not damaged, and and semantic the part where you csn see objects is damaged processing needed to interpret sensory information Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J https://youtu.be/ze8VVtBgK7A?si=McDEeOw6vxuw3Mja CRICOS Provider Code 00301J  Gibson’s theory of direct perception Gibson (1966) one of the main proponents of bottom- up/ecological/direct perception Perception is innate rather than learned Information we need to form perceptions is contained in the environmental stimuli – e.g., texture gradient that is perceived as distance… gives us enough info to work out; dont need any details Not smaller stones, the same stones but further away Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  The further away the slower the flow Note: length of arrow indicates speed of flow The pattern is specific to the type of movement CRICOS Provider Code 00301J  Top-Down Processing In bottom-up processing, we allow the stimulus itself to shape our perception, without any preconceived ideas. In top-down processing, we use our background knowledge and expectations to interpret what we see. CRICOS Provider Code 00301J  Constructivist/Top-Down Processing Perception a process of taking fragments of information and constructing meaning somesort of guidance it determiones what this picture is Example: Experience, expectations – i.e., top-down Perceptual decision Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Constructivist/Top-Down Processing Perception a process of taking fragments of information and constructing meaning Example: Experience, expectations – i.e., top-down Perceptual decision Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Top-Down Processing Construct representation from fragments of sensory info  Perceptionis not passive - we actively interpret information to understand  We perceive more than sensory information would allow alone Perception is guided by higher-order cognitive processing  Schemas  Interpreting sensory information is not objective  Past experiences (memory), expectations (including priming, knowledge & beliefs (world models), motivation, beliefs Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Top-Down Processing Context shapes/determines perception contxt changes, we see things different (perception changes) Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Top-Down Processing Saves brain power – basically allows us to make perceptual inferences without necessarily having to process all the details contrains the information that we are willing to process. if we had to reconstruct a whole image, it requires a lot of effort, and processing processing what we are expecting to see But accurate? Perception is often an educated guess Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Implications of Top-Down Processing Perception is complex - raw sensory information complex mental processes Perception is subjective  Can be incorrect (not an accurate representation of the “real world”  Influenced by context  But top-down processing is more efficient Sensation and perception are two very different processes  Perception = interpreting sensations Note: applies to all types of perception, not just visual Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Interaction both of those things can be true feature detectors to detect lines Bottom-up processing of features, shapes, colour, etc. Top-down (constructivist/intelligent) processing – impart knowledge, and expectations onto incoming sensations/neural activation. construct things based on knowledge: saves time Both are involved in perception Using models, ideas, expectations Top-down to interpret sensory stimuli Taking sensory information, Bottom-up combining and integrating it Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Signal Detection Theory Links to bottom-up versus top-down theories helps us understand when and how people detect things at what point will i no longer be able to detect iot CRICOS Provider Code 00301J  Detecting signals… The most basic task for any sensory system is detecting the presence/alteration of energy changes  Detecting stimuli is required for perception  The inputs are electromagnetic (light), mechanical (sound, touch), chemical (taste, smells), thermal (touch) According to bottom-up theory: how higher,lower sound is  If the stimulus activates our senses, then we perceive the signal  If the stimulus does not activate our senses, we do not perceive the signal minimum amount Absolute Threshold – minimum amount of energy needed to detect of light or sound stimulus 50% of time if you show a timukus at 100 trials 50% of times they can see/recognise it Just Noticeable Difference (JND) - smallest change in the intensity of a stimulus that we can detect same stimulus doesnt get More change needed with higher amounts of the stimulus picked up  everytime Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Absolute Thresholds (Fechner, 1966) Early ‘either-or’ viewpoint of threshold is incorrect 100 ‘yes’ responses You either detect it Proportion The response 0 or you don't detect it 0 1 2 3 4 5 6 7 because we live in a nosiy environment; stimulus intensity backgroun noise in our neural system impacting if we can detect the stimulus or not with probability; not 100% of the time you can pick it up CRICOS Provider Code 00301J  Some Common Absolute Thresholds SENSE THRESHOLD Vision A candle flame from a distance of 48km on a dark clear night Hearing A ticking watch in a quiet room at a distance of 6m Taste One teaspoon of sugar dissolved in 7.5 litres of water Smell One drop of perfume diffused through three room apartment Touch The wing of a fly falling on your cheek from a height of 8.5 cm Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Detection…if expected Response Signal Yes No Signal present 90% of the time Present.95.05 influenced by our Absent.63 when there was.37 expectations nothing there were led to Response expect a stimulus Signal Yes No Signal present Present.35.65 10% of the time were not Absent.04.96 expectimg and behaviour and perception has changed Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Signal detection - Conclusion Observer is involved in cognitive act of making a decision as to whether a stimulus is present or absent  No real absolute threshold  Detection depends on the context and the person The most basic of perceptual acts – determining whether a signal is there – has a top-down component! Motivation and expectancies affect perceptual judgements as much as stimulus reception itself Note also: perception can occur without sensation (false “yes” responses) We are not passive observers/perceivers of stimuli Bernstein et al. (2012); Burton et al. (2015); Lilienfeld et al. (2012; Passer and Smith (2019) CRICOS Provider Code 00301J  Summary Difference between sensation & perception Theories of perception  Bottom up  Top-down Take home message: Perception is a complex, active process that despite being so quick and apparently automatic, actually requires a large amount of our cognitive resources, and is partly under our influence. CRICOS Provider Code 00301J  References Bernstein, D. A., Penner, L. A., Clarke-Stewart, A., & Roy, E. (2012). Psychology (9th ed.). Wadsworth. Burton, L., Weston, D., & Kowalski, R. (2015). Psychology (4th ed.). John Wiley & Sons. Coren, S., Wards, L. M., & Enns, J. T. (2003). Sensation and perception (6th ed.). John Wiley and Sons Fechner, G. T. (1966). Elements of psychophysics. Holt, Rinehart, and Winston. Gibson, J. J. (1966). The senses as perceptual systems. Houghton Mifflin. Goldstein, E. B. (2014). Sensation and perception (9th ed.). Wadsworth Cengage Learning. Lilienfeld, S. O., Lynn, S. J., & Namy, L. L. (2012). Psychology: From inquiry to understanding (2nd ed.). Pearson/Allyn & Bacon. Passer, M. W., & Smith, R. E. (2019). Psychology: The science of mind and behaviour (3rd ed.). McGraw Hill. CRICOS Provider Code 00301J