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8/23/2024 Experimental Psychology 530038-B-6 1st year Bachelor Psychology Cognitive Psychology...
8/23/2024 Experimental Psychology 530038-B-6 1st year Bachelor Psychology Cognitive Psychology 840103-B-6 2nd year Bachelor Liberal Arts & Sciences Course Information dr. Martijn Baart - Lectures & Exam (course coordinator) dr. Jeroen Stekelenburg & dr. Mirjam Keetels - Practical Experimental Skills 2 Course Information Principles when interacting with me/each other during this course - Agree to disagree is OK; - Respect goes a long way; - We all make mistakes – don’t assume bad intentions. 3 1 8/23/2024 Course Information Literature (see Osiris) Schacter, D, Gilbert, D., Wegner, D., & Hood, B. (2020). Psychology: 3rd European edition. Red Globe Press. (ISBN 978-1-352-00483-0) Digital version is available from publisher for £42,99 (hardcopy is £55,99): - https://www.macmillanlearning.com/ed/uk/produ ct/Psychology-3rd-edition/p/1352004836 - Use coupon code SC2524OK to obtain a 25% discount. 4 Course Information Literature (see Osiris) Schacter, D, Gilbert, D., Wegner, D., & Hood, B. (2020). Psychology: 3rd European edition. Red Globe Press. (ISBN 978-1-352-00483-0) Chapter 1: pages 3-45: (Psychology; the evolution of a science) Chapter 2: pages 47-90 (The methods of psychology) Chapter 3: pages 93-136 (Neuroscience and behavior) Chapter 4: pages 139-188 (Sensation and Perception) Chapter 5: pages 191-234 (Memory) Chapter 6: pages 237-277 (Learning) Chapter 7: pages 279-323 (Language and Thought) Chapter 8: pages 325-370 (Consciousness) Chapter 9: pages 373-406 (Intelligence) Chapter 10: pages 409-444 (Emotion and Motivation) Chapter 11: pages 447-490 (Cognitive development) Chapter 12: pages 493-536 (Social development) Chapter 13: pages 539-573 (Personality) Chapter 14: pages 575-611 (Social Relationships) Chapter 15: pages 613-647 (Social groups) Chapter 16: pages 649-689 (Psychological disorders) Chapter 17: pages 639-734 (Mental health) 5 Course Information Literature (see Osiris) Schacter, D, Gilbert, D., Wegner, D., & Hood, B. (2020). Psychology: 3rd European edition. Red Globe Press. (ISBN 978-1-352-00483-0) Chapter 1: pages 3-45: (Psychology; the evolution of a science) Study thoroughly Chapter 2: pages 47-90 (The methods of psychology) Study thoroughly Chapter 3: pages 93-136 (Neuroscience and behavior) Read pages 94-124, Study pages 125-134 thoroughly Chapter 4: pages 139-188 (Sensation and Perception) Study thoroughly Chapter 5: pages 191-234 (Memory) Study thoroughly Chapter 6: pages 237-277 (Learning) Study thoroughly Chapter 7: pages 279-323 (Language and Thought) Study thoroughly Chapter 8: pages 325-370 (Consciousness) Study thoroughly Chapter 9: pages 373-406 (Intelligence) Feel free to read Chapter 10: pages 409-444 (Emotion and Motivation) Study thoroughly Chapter 11: pages 447-490 (Cognitive development) Feel free to read Chapter 12: pages 493-536 (Social development) Feel free to read Chapter 13: pages 539-573 (Personality) Feel free to read Chapter 14: pages 575-611 (Social Relationships) Feel free to read Chapter 15: pages 613-647 (Social groups) Feel free to read Chapter 16: pages 649-689 (Psychological disorders) Feel free to read Chapter 17: pages 639-734 (Mental health) Feel free to read 6 2 8/23/2024 Course Information The exam (see next slides) is based on the slides (which are based on the book) - When there is more information on the slides than in the book, the slides are leading. - In case you cannot follow the line of thought on the slides, please turn to the book. - Certain sections of the book are not discussed on the slides. When these sections are fair game for the exam, this is explicitly mentioned on the slides. Book section not discussed and not explicitly mentioned on slides that you should study the book? → Not in exam exam Book section not discussed but explicitly mentioned on slides slides that you should study it? → Fair game for exam Book section discussed on slides but slides unclear to you? → Turn to the book → Fair game for exam 7 Course Information Practice materials for each chapter are available on Canvas: - Open questions (+ answers) - Exercises (+ answers) → Self study (optional) Passing this course requires: 1) Passing the exam (>34 out of 50 MC questions answered correctly) → Short mock exam (+ answers) is available on Canvas 2) A ‘pass’ for the Practical Experimental Skills (1 re-sit opportunity, result remains valid for next year) 8 Course Information Register for the exam ASAP! First opportunity: October 18, 2024 Re-sit: January 10, 2025 The exam dates are also the deadlines for the Experimental Skills report 9 3 8/23/2024 Course Information Practical Experimental Skills - 6 weeks, 6 sessions (1st session [next week] is online) - You can do the work at home or at any TiU computer (the assignments are self- explanatory). - Questions about the materials can be asked on campus (during the practical sessions - emails will not be answered). - The report should be uploaded before/on the date of the first exam opportunity. More information is available on Canvas. 10 Chapter 1 Experimental/Cognitive psychology Psychology: the scientific study of mind and behavior. - mind: private inner experience of perception, thoughts, memories and feelings. - behavior: observable actions of human beings and non- human animals. Experiment: a technique of establishing a causal relationship between variables. For definitions, see pages 736-750 in the book (glossary) Experimental/Cognitive psychology: the scientific study of mind and behavior by means of experiments. 11 Chapter 1 Experimental/Cognitive psychology How to study mind and behavior? → Focus on cognitive functions Cognition: all mental processes that lead to thoughts, knowledge, and awareness. Cognitive processes: mechanisms that underly cognition. Cognitive processes govern Cognitive functions like attention, memory, learning, decision-making, language, perception, motor-skills, imagination, etc. 12 4 8/23/2024 Chapter 1 Experimental/Cognitive psychology Cognitive functions are the ‘building blocks’ of all complex behavior (like ‘eating peas’). This task requires: - Perception - Decision making - Motor skills - Attention - …….etc. 13 Chapter 1 Experimental/Cognitive psychology Experimental psychology is closely linked to Cognitive neuropsychology: - Patients with (local) brain damage allow for more specific and reliable inferences about brain functioning. e.g. patients with - neglect (hemi spatial/unilateral inattention) - aphasia (trouble producing or understanding speech) - dyslexia (trouble with reading [and auditory speech perception]) - prosopagnosia (inability to recognize faces [object recognition is fine]) - visual agnosia (inability to recognize visual objects [but not faces]) 14 Chapter 1 Experimental/Cognitive psychology Cognitive neuroscience attempts to understand the biological foundations of cognition (the main idea is that cognitive processes produce brain activity that can be tracked and traced). 15 5 8/23/2024 Chapter 1 Brief history Greek philosophers ~400 BC Enlightenment (17th and 18th century, Western Europe) Continental rationalists British empiricists (knowledge is innate or inborn: nativism) (knowledge is acquired) Benedict de Spinoza John Locke Gottfried Leibniz George Berkeley René Descartes David Hume Dualism: The mind is not supreme: body and mind are separate entities* that interact (via the pineal gland). *e.g., because bodily reflexes do not involve the mind/free will, the body and mind must be distinct. 16 Chapter 1 Brief history In the 19th century, Psychology started to evolve into a science One of the first psychologists to conduct experiments was Hermann von Helmholtz (1821-1894). He studied, for example, the conduction velocity of the nerve impulse. Inspired by Ernst Weber (1795–1878), Gustav Fechner (1801-1871) introduced the Just Noticeable Difference (JND), which is still widely used in psychophysics. JND: the minimum difference in stimulation that a person can detect 50% of the time (more on this later). 17 Chapter 1 Brief history Franciscus Donders (1818-1889, from Tilburg) introduced Mental Chronometry - How much time do you need to decide whether you heard the syllable ‘ka’, ‘ta’, or ‘pa’? (1) Simple reaction time: press a button whenever you hear a syllable (RT = 198 ms). → DETECTION RT (2) Differential/choice reaction time: press ‘k’ when you hear ‘ka’, press ‘t’ when you hear ‘ta’, press ‘p’ when you hear ‘pa’ (RT = 278 ms). → DETECTION RT + DISCRIMINATION RT + DECISION RT (3) Go/No go reaction time: press ‘k’ when you hear ‘ka’, but do nothing when you hear ‘ta’ or ‘pa’ (RT = 269 ms). → DETECTION RT + DISCRIMINATION RT The time you need for stimulus This additive factor logic is still used in discrimination = (3) – (1) = 71 ms, and the time you need only for decision modern day research where brain making = (2) – (3) = 9 ms. activity (measured with EEG or fMRI, for Time you need to make a decision that example) in an experimental condition is includes discrimination = (2) – (1) = 80 ms. subtracted from a control condition or when two experimental conditions are subtracted 18 6 8/23/2024 Chapter 1 Brief history In the 19th & 20th centuries, several competing schools emerged Structuralism: consciousness should be the focus of study via analyses of the basic elements that constitute the mind (Wilhelm Wundt; 1832- 1920). - Achieved by breaking down consciousness into sensations and feelings via analytical introspection: - Some melody is played to a participant: “I hear tones of different duration, pitch and loudness (sensations), that are structured in an unfamiliar rhythm which makes me feel confused (subjective interpretation/feelings). - Further developed by Edward Titchener (1867-1927) who proposed 3 elementary states of consciousness (Sensations [sights, sounds, tastes], Images [components of thoughts], and Affections [components of emotions]) and identified thousands of ‘elemental qualities of conscious experience’. 19 Chapter 1 Brief history Behaviorism (John Watson, 1878-1958): The introspective processes cannot be studied (too vague and subjective) and overt behavior (what people do) should be studied instead because: - The only way to understand animal and human learning and adaptation is to focus solely on their behavior; - Behavior can be observed by anyone and measured objectively; - The goal of scientific psychology is to predict and control behavior in a way that benefits society. 20 Chapter 1 Brief history Behaviorism was a part of the logical positivism movement that introduced the operational definition: A description of a/an (abstract) property in terms of a concrete condition that can be measured. Abstract property Condition Hunger Number of hours deprived from food Height of a person Number of cm measured from feet to crown Addiction Number of diagnostic criteria for a substance use disorder that are Operational definitions have met big advantages as they allow for precise measurements Weather and direct Thecomparisons between highest recorded temperature studies between sunset(replications). and sundown measured in degrees Celsius But, operational Violent crime definitions are not The number always of people good that were definitions arrested in a given day (clear for murder, forcible rape, robbery, and aggravated assault measurable conditions can still be quite useless): - happiness is the number of smiles during a specific episode. - age is the response that participants provide on a questionnaire. 21 7 8/23/2024 Chapter 1 Brief history Ivan Pavlov, (1849-1936): Classical conditioning US (or UCS) = unconditioned stimulus that produces an UR (or UCR) = unconditioned response When the US is repeatedly paired with another (neutral) stimulus, the other (neutral) stimulus becomes a CS = conditioned stimulus that produces a CR = conditioned response which is the same as the UR but now occurs without the original US. 22 Chapter 1 Brief history Skinner (1904-1990): Operant conditioning Learning occurs through reinforcement and punishment, that can both be positive (something is added) or negative (something is removed) Reinforcement Punishment Increase behavior Decrease behavior Positive Positive reinforcement punishment Add stimulus (e.g., Add stimulus (e.g., money, food etc.) pain, stress etc.) Negative Negative reinforcement punishment Remove stimulus Remove stimulus (e.g., pain, stress) (e.g., food, money) 23 Chapter 1 Brief history Gestalt psychology: Max Wertheimer (1880-1943), Wolfgang Köhler (1887-1967) and Kurt Koffka (1886-1941). Key principle: The whole is more than the sum of its parts They rejected: - Wundt’s structuralism (because experience is more than a function of sensation); - Behaviorism, because complex behavior (“the whole”) is more than the sum of its components. 24 8 8/23/2024 Chapter 1 Brief history Gestalt psychologists use apparent motion to prove their point (phi phenomenon, Wertheimer 1912, https://www.youtube.com/watch?v=-zbzt7Cb2e4). https://web.mit.edu/bcs/schille rlab/book/11-3.html https://web.mit.edu/bcs/schillerl ab/book/11-5.html Perception is a construction, not a reflection of the sensation. Also in the auditory domain: you can either hear a galloping-rhythm when 2 tones (high-high-low-high-high-low-high…etc.) are played, or you hear 1 high stream and 1 low stream (especially when pith difference is large) 25 Chapter 1 Current era Since 1970’s: Cognitive revolution Computer is used as a metaphor for human thinking Since 1980’s: Modern imaging techniques available Testing neuropsychological patients (single-case and group studies) can help to answer theoretical (general) hypotheses. Magnetic Resonance Imaging (MRI) Structural MRI Functional MRI 26 Chapter 2 Empiricism Empiricism: Acquiring knowledge requires observation Scientific Method: Observations can lead to mistakes, false conclusions and illusions, so we need a set of rules and techniques to avoid those. (1) Theorize/generate idea → often based on literature/previous experience → use principle of parsimony/Ockham’s [Occam’s] razor) (2) Formulate falsifiable hypothesis → If … is true, we should observe …. (specific, verifiable) (3) Collect and analyze data → observations in a lab or in the real world, using specific techniques → operationalization should be concrete [many critical choices to make!]) (4) Draw conclusions regarding hypothesis → Results align with hypothesis? Confirm theory. → Results do not align with hypothesis? Theory is wrong (falsification) or mistakes in operationalization 27 9 8/23/2024 Chapter 2 Empiricism Deduction: Drawing inferences based on premises (assumptions) Premise: All organisms die general Premise: John is an organism Conclusion: John will die specific Problem: we cannot observe all organisms to figure out whether or not they die, so we must use induction: Premise: My dog died specific Premise: My tomato plant died Premise: etc… Conclusion: All organisms die general Problem: more observations cannot make a statement more true because unencountered exceptions may arise (David Hume). Conclusion can only proven to be false (Karl Popper). 28 Chapter 2 Empiricism Humans are difficult to study - Complexity: thoughts, feelings, action driven by 500 million neurons; not well understood yet - Variability: All else being equal, individuals are very different - Reactivity: People under observation react differently than when alone 29 Chapter 2 Observation Before understanding why people do things, we need to know what they’re actually doing. - Define property (of behavior) you wish to observe by means of operational definition (see slide #21) - Detect/measure that property by using a tool/measure that is able to detect the event to which the operational definition refers - A tool/measure should produce the same result whenever it is used to measure the same property. If not: problem with reliability. 30 10 8/23/2024 Chapter 2 Observation Observing the entire population is impossible, so we draw samples to be able to compute an average based on many observations. When the number of observations increase, the sample properties will reflect populations properties more closely. Central tendency: - Mode: most occurring value in sample (N=5: 7,7,7,8,9 mode = 7) - Median: value that splits data-file in two (median = 7) - Mean: arithmetic average (mean = 7.6) How much do observations differ from each other? - Variance and standard deviation BOOK: PAGE 56-57 31 Chapter 2 Observation These values can be used as input for many statistical tests to assess hypotheses. - p-value <.05: We reject H0 and accept H1 Type I error: an observed effect is not real Type II error: an observed null-effect is not real (there actually is an effect) 32 Chapter 2 Observation Bias (tendency to display certain behavior): - Demand characteristics: in an observational setting, people behave in a way that meets expectations or beliefs about desired outcome; participants have beliefs about what the researcher is ‘demanding’ of them. - Students provide high scores on a stress questionnaire because they believe this is what they are supposed to do. - An experiment is entitled “Effects of physical pain on mood” → participants anticipate that they are supposed to feel bad after feeling pain. Observers can also be biased - A coach believes that a track and field athlete is going to be particularly fast today, which can influence the coach’s behavior (shouting louder, providing athlete with convincing pep-talk, etc.) 33 11 8/23/2024 Chapter 2 Explanation Correlation: variations on one variable are synchronized with variations in another variable (variables ‘change together’). - Positive (+1 = perfect positive correlation): variables change in the same direction → time spent studying & exam grade → sunlight hours & leaf growth - Negative (-1 = perfect negative correlation) is : variables change in opposite directions → age & hearing ability → days in rehab & substance abuse - Uncorrelated: no systematic pattern in variable changes → driving skills & favorite color of shoe laces → length of index finger & money spent on groceries 34 Chapter 2 Explanation Strong correlation → weak correlation Negative Positive 35 Chapter 2 Explanation Causal relationship: a change in some variable is causing a change in another variable (the cause must precede the effect). Independent variable (X; Cause) Dependent variable (Y; Effect) Food packaging shelf life Amount of water in soil plant growth Wind strength wave height Task difficulty reaction time Hours emersed in combat situation PTSS 36 12 8/23/2024 Chapter 2 Explanation Many variables are correlated, even when relationship seems bizarre: correlation is no evidence for causation (third variable problem). 37 Chapter 2 Explanation Many variables are correlated, even when relationship seems bizarre: correlation is no evidence for causation (third variable problem). 38 Chapter 2 Explanation But how about less bizarre examples? Again: correlation is no evidence for causation. “Television viewing and aggressive behavior were assessed over a 17-year interval in a community sample of 707 individuals. There was a significant association between the amount of time spent watching television during adolescence in early adulthood and the likelihood of subsequent aggressive acts against others”. Science, 2002, Mar 29;295(5564):2468-71 - maybe, watching tv → aggression - maybe, aggressive people simply like to watch more tv (aggression → watching tv) - maybe, watching a lot of tv leads to boredom, and boredom requires people to blow-off steam (tv → boredom → aggression) - maybe, people with lower socioeconomic status (SES) watch more tv, and are more aggressive (SES → tv and aggression) 39 13 8/23/2024 Chapter 2 Explanation But how about less bizarre examples? Again: correlation is no evidence for causation. The Guardian, August 14, 2007 - maybe, obesity → disruption of hormonal balance → infertility - maybe, disruption of hormonal balance → infertility → obesity (negative emotions caused by infertility lead to overeating) - maybe, disruption of hormonal balance leads to both infertility and obesity (hormonal imbalance → infertility & obesity) - maybe, body fat is an effective anti-conceptive - etc. 40 Chapter 2 Explanation But how about less bizarre examples? Again: correlation is no evidence for causation. https://www.all-creatures.org/health/cancerand-bres.html - Causal relationships or not….? Recognize your personal bias and be critical! 41 Chapter 2 Explanation Experimentation: techniques that allow for establishing whether a causal relationship exists Manipulation: creating a pattern of variation in an independent variable (X) to establish changes in Y (dependent variable). Some examples: - Number of words presented (X) in a memory recall test (% of recalled items = Y). - Number of distractors (X) in a visual search task (target localization speed = Y) - Levels of masking noise (X) in a speech recognition task (# of correctly recognized items = Y). Manipulations can be made within-subjects (all participants in an experiment receive 6 levels of masking noise) or between-subjects (i.e., multiple samples are tested → 3 treatment types for anxiety: none, antidepressants, cognitive therapy) 42 14 8/23/2024 Chapter 2 Explanation Example: Does watching tv cause aggressive behavior in children? within-subjects Between-subjects within-subjects measurement manipulation measurement 1) Watch non-violent tv for 2 hours a day (3 weeks) Aggressive behavior 2) Watch violent tv for 2 hours a day (3 weeks) Aggressive behavior 3) Read non-violent books for 2 hours a day (3 weeks) 43 Chapter 2 Explanation Example: Does watching tv cause aggressive behavior? within-subjects Between-subjects within-subjects measurement - If watching tv causes aggressive behavior: manipulation measurement - Increase1)inWatch aggression non-violent(i.e., tv forthe difference 2 hours in aggression a day (3 weeks) measured before/after assigning kids to groups) should be stronger for both tv groups relative to the reading group Aggressive behavior 2) Watch violent tv for 2 hours a day (3 weeks) Aggressive behavior - If watching violent tv causes aggressive behavior: - Increase in aggression (i.e., the difference in aggression measured before/after assigning kids to groups) should be stronger3)for Read non-violent books for 2 hours a day (3 weeks) the violent tv group relative to the non-violent tv and reading group 44 Chapter 2 Explanation Randomization: Assigning participants to a sample is not determined by a third variable; all members of the population of interest have an equal chance to be selected in the sample. A problem in psychology? - WEIRD participants (see Chapter 1, page 35) are not representative of the human race (~16%) - Yet, 96% of samples studied in psychology consist of WEIRD people 45 15 8/23/2024 Chapter 2 Drawing conclusions Internal validity should be sufficient (related to factors within the experiment): The experiment should be designed and carried out in such a way that inferences about causal relationship between X and Y are accurate (related to operationalization, see slide #27). External validity should be sufficient (related to generalizability of the results): The causal relationship between X and Y should be constant across samples, cultures, etc. 46 Chapter 2 Drawing conclusions Validity (measuring what you wish to measure) vs. reliability (consistency of measure) × ××× × × × × × × × × ×× × × × ×× × × × × × valid not valid valid not valid reliable reliable not reliable not reliable 47 Chapter 2 Quantitative/qualitative research Quantitative: measures represent values or counts expressed as numbers (RT, errors, proportion correct [accuracy]). - Systematic scientific investigation in order to quantify phenomena. Qualitative: measures represent assigned names, labels or values (analyzing interviews, personal accounts from an observer). - Detailed insights in individual experiences, understanding, motivation, thoughts, feelings etc. 48 16 8/23/2024 Chapter 3 The human brain Basic organization Two hemispheres connected by the corpus callosum 49 Chapter 3 The human brain Basic organization: White versus grey matter Basic organization: The neuron Dendrites are short and branched in appearance - axons are much longer. In general, dendrites receive signals, and axons transmit them. Most neurons have a lot of dendrites and only have one axon. 50 Chapter 3 The human brain Basic organization Interactive brain model: http://www.brainfacts.org/3D- Brain#intro=false&focus=Brain 51 17 8/23/2024 Chapter 3 Investigating the brain Studying the damaged brain produces valuable insights about its organization Paul Broca (1861): patient with specific damage in left frontal lobe lost ability to produce spoken language, but understanding of speech was intact. Carl Wernicke (1874): patient with specific damage in upper-left temporal lobe had impaired understanding of language, but could produce speech. 52 Chapter 3 Investigating the brain Studying the damaged brain produces valuable insights about its organization Phineas Gage (1848): quiet, conscientious, well- mannered prior to accident, vs. irresponsible, indecisive, irritable, use of profane language after accident Frontal lobe involved in executive functioning (planning, memory, inhibition attention) - A typical example of an executive functioning task: Stroop task Name the color of the text font as quickly as you can BLUE GREEN RED vs. GREEN BLUE RED 53 Chapter 3 Investigating the brain Studying the damaged brain produces valuable insights about its organization Split brain patients: corpus callosum (thick band of nerve fibers that allow hemispheres to communicate) severed Background info on the Visual pathway: right visual field processed in left hemisphere, and vice versa (more later) 54 18 8/23/2024 Chapter 3 Investigating the brain Measuring brain structure Computerized axial tomography (CT scan): multiple X-rays combined into a single image https://www.youtube.com/watch?v=l9s https://nl.wikipedia.org/wiki/ wbAtRRbg Computertomografie 55 Chapter 3 Investigating the brain Measuring brain structure Magnetic Resonance Imaging (MRI): powerful magnet causes charged molecules to re-align to produce field distortions that can be measured. https://www.youtube.com/watch?v=n www.bcbl.eu FkBhUYynUw 56 Chapter 3 Investigating the brain Measuring brain activity Single-cell recordings: activity (action potential, or ‘firing’) of a neuron measured by an electrode - high temporal resolution, precise localization Ludvig et al. (2011) 57 19 8/23/2024 Chapter 3 Investigating the brain Measuring brain activity Electroencephalography (EEG): electrodes on the scalp detect electrical activity (voltage fluctuations resulting from ionic [sodium] currents in the neurons, mostly in pyramidal cells located in the outer layers of the cerebral cortex) – high temporal resolution, relatively poor localization https://www.youtube.com/watch?v=7 Nagel, S. 2019). Towards a home-use BCI: fast asynchronous control and robust non-control state detection. Doctoral 1523EZb8Rg dissertation. Doi: 10.15496/publikation-37739. 58 Chapter 3 Investigating the brain Measuring brain activity Magnetoencephalography (MEG): measures magnetic fields produced by electrical brain activity (i.e., the flow of electrically charged ions through neurons [ionic current flow] produces electromagnetic fields)– high temporal resolution, good localization https://www.youtube.com/watch?v=v www.bcbl.eu JdGIyMA-Pw 59 Chapter 3 Investigating the brain Measuring brain activity functional Magnetic Resonance Imaging (fMRI): activated brain regions need energy which is supplied by blood, fMRI detects changes in blood flow) – relatively poor temporal resolution, good localization https://www.youtube.com/watch?v=n www.bcbl.eu FkBhUYynUw 60 20 8/23/2024 Chapter 3 Investigating the brain Measuring brain activity Positron emission tomography (PET): measure blood flow in the brain via radioactive markers – relatively poor temporal resolution (currently a few seconds at best), good spatial resolution https://www.youtube.com/watch?v=G https://www.olvz.be/nl/pet-centrum-zuidoost- vlaanderen/wat-is-een-pet-scan-zijn-er-risicos HLBcCv4rqk 61 Chapter 3 Investigating the brain Altering brain activity Transcranial magnetic stimulation (TMS): uses magnetic fields to stimulate or inhibit nerve cells (often a therapeutic implementation [TMS can reduce depression]) https://www.youtube.com/watch?v=NQHVfF_5rtc https://brainclinics.com/rtms/ 62 Chapter 3 Investigating the brain Altering brain activity Transcranial direct current stimulation (tDCS): stimulate parts of the brain by applying (low intensity) electrical currents (often a therapeutic implementation) https://neuromtl.com/technolo gy/transcranial-direct-current- https://www.youtube.com/watch?v=Lv1fFcrveqY stimulation-tdcs/ 63 21 8/23/2024 Chapter 4 Sensation & perception Sensation: awareness of stimulus due to stimulation of a sense organ Perception: organization, identification and interpretation of a sensation to form mental representations Usually, sensation and perception happen so quickly that ‘seeing’ equals ‘understanding’. When dealing with ambiguous figures, however, the time between seeing and understanding can be separated. 64 Chapter 4 Sensation & perception Traditionally: 5 senses Additionally: - kinesthetics (limb posture and muscle tension) - balance - Touch includes texture, pain, temperature https://ercare24.com/wp- content/uploads/making-the-most-of-your-five- senses.jpg 65 Chapter 4 Sensation & perception Psychophysics: Methods that measure the strength of a stimulus and the observer’s sensitivity to that stimulus (Gustave Fechner, see slide #17). - Present light flashes at various brightness levels and ask participants to indicate whether they saw a flash or not - Present tones at various intensity levels and ask participants to indicate whether they heard a tone or not - …. Absolute threshold: Minimal intensity required to (just) detect a stimulus. - Threshold = successful detection on 50% of trials 66 22 8/23/2024 Chapter 4 Sensation & perception How absolute is absolute? There is some detection in the green area (and 50% at threshold). No binary on/off system due to: - competition/noise (from other sensory input) - response criterion (respond ‘yes’ for obvious stimulation only, or also for faint stimulation?) → someone willing to say ‘yes’ has lower threshold than someone with stricter criterion. 67 Chapter 4 Sensation & perception Just Noticeable Difference (JND): the minimum difference in stimulation that a person can detect 50% of the time (compare a standard stimulus to another one). - Weber’s law (Weber/Fechner’s law): JND is a constant proportion of the standard – this proportion is called the Weber fraction 68 Chapter 4 Sensation & perception A small Weber fraction implies good sensitivity Decreasing the amount of salt in food by < 8.3% should go undetected 69 23 8/23/2024 Chapter 4 Sensation & perception There is often a transition from not observing a stimulus to observing a stimulus. Moreover, there always is a response bias (preference for responding ‘yes’ or ‘no’) when testing individuals. Signal detection theory (SDT): assumes that a stimulus is always presented against a background of (internal) noise. Stimulus activity is added to the constant noise signal. The individual decides whether the observed activity originates from ‘noise alone’ or from ‘stimulus + noise’, and uses a criterium for this (4 possibilities): Was there a stimulus present? 70 Chapter 4 Sensation & perception Signal detection theory (SDT): - Liberal response criterion: Many hits, but also many False alarms. Response (%) Yes no Stimulus 87% 13% present Stimulus not present 71% 29% 71 Chapter 4 Sensation & perception Signal detection theory (SDT): - Conservative response criterion: Many Correct rejections, but also many Misses. Response (%) Yes no Stimulus 35% 65% present Stimulus not present 17% 83% 72 24 8/23/2024 Chapter 4 Sensation & perception D-prime (D’ or d’): A measure of sensitivity (ability to detect signals). D’ = 0? → performance at chance level. D’ = 3? → close to perfect https://gru.stanford.edu/doku.php/tutorials/sdt 73 Chapter 4 Sensation & perception Signal detection theory (SDT): - Liberal response criterion: Many hits, but also many False alarms. D’ = 0.58 - Conservative response criterion: Many Correct rejections, but also many Misses. D’ = 0.57 Sensory adaptation: sensitivity declines after prolonged exposure. 74 Chapter 4 Sensation & perception Signal detection theory (SDT) is also relevant for (research on) the quality of decisions we make in society: - Where do we set the criterion for accusing a suspect of a crime? What are the costs of releasing a guilty person (miss) versus those of incarcerating an innocent person (false alarm)? - When do we perform surgery? What are the costs of not performing surgery when it is necessary (miss), versus performing unnecessary surgery (false alarm)? - When is a submarine sonar operator supposed to decide whether a signal represent a hostile threat? What are the costs of not acting in the presence of a hostile vessel (miss) versus acting when there is no actual threat (false alarm)? - Etc. 75 25 8/23/2024 Chapter 4 Our senses: Vision Light is electromagnetic radiation with a specific frequency that falls within the observable spectrum (i.e., is visible to the eye). - Wavelength usually expressed in nanometers (1 nm = 1 billionth of a meter) 76 Chapter 4 Our senses: Vision The human eye https://www.ted.com/talks/joshua_harvey_the_evolution_of_th e_human_eye 77 Chapter 4 Our senses: Vision The human eye 78 26 8/23/2024 Chapter 4 Our senses: Vision The human eye Light first passes through the cornea. The cornea protects the structures inside the eye, and refracts and bends the light rays. This happens because the cornea tissue is denser than air (the density of the cornea is similar to the density of water → refractive function of cornea is lost under water → blurry vision). 79 Chapter 4 Our senses: Vision The human eye The pupil is an opening in the iris. It appears to be black because light that enters the eye is absorbed by the retina (when light is extremely bright, it may reflect back through the pupil → red pupils on pictures taken with flash). The size of the pupil (controlled by muscles in the iris) determines how much light enters the eye. 80 Chapter 4 Our senses: Vision The human eye After the light passes through the cornea, it is refracted/bent again by the lens (a fine-tuning; about 20% of refraction happens in lens, 80% happens in cornea) to focus light on the retina (achieved by ciliary muscles that bend or flatten the lens). 81 27 8/23/2024 Chapter 4 Our senses: Vision The human eye Light The inside lining of the eye is the retina. The retina comprises ~130 million light-sensitive receptors that are responsible for signal transduction (from light to a neural response). Around 7 million receptors are cones, the other 123 million are rods. Light passes through ganglion cells and bipolar cells before reaching the cones/rods. 82 Chapter 4 Our senses: Vision Cones versus rods Cones are mostly packed in the ‘pit’ (fovea) in the central part of the retina (macula) Cones are responsible for perception of color and fine details (foveal vision is central and sharp). 83 Chapter 4 Our senses: Vision Cones versus rods Rods are mostly centered around the fovea and are sensitive to low- intensity light. Rods are colorblind and responsible for perception of movement, peripheral vision (lower resolution than foveal vision) and night vision. The distribution of rods and cones on the retina. 84 28 8/23/2024 Chapter 4 Our senses: Vision As noted, light first travels through ganglion cells (some light is absorbed*) and bipolar cells before reaching the cones/rods. The compressed information (compression is lowest in macula/fovea [cones] and highest in periphery [rods]) from the cones/rods is sent to the optic nerve via these bipolar and ganglion cells. Light Compressed * This information information plays a role in governing pupillary diameter and in the body’s circadian rhythms 85 Chapter 4 Our senses: Vision The information thus travels inside the eye and needs to leave it at some point. Where the optic nerve leaves the eye (the optic nerve head or optic disk), there is a blind spot (discovered by the anatomist Mariotte in 1668). Light Compressed Blind information spot 86 Chapter 4 Our senses: Vision Cephalopods don’t have a blind spot as retinal axons pass over the back of the retina. Our brain fills in the blind spot with the immediate surrounds. 87 29 8/23/2024 Chapter 4 Our senses: Vision Want to ‘see’ your blind spot? - Put thumbs together and stretch out index fingers - Stretch arms - With right eye look to left finger - Wiggle right finger (it should disappear) Or: look at center of this image (on your screen), cover left eye, look with right eye to cross, move closer to/away from the screen. At some point, the circle will disappear, but the brain fills in the yellow background color (remember, there are no cones involved in peripheral vision, so no actual color vision is possible). 88 Chapter 4 Our senses: Vision Problems with the eye Hyperopia (hypermetropia): Eye is too short, focal plane (where light is focused) lies behind retina: the person is farsighted and cannot focus on close objects (corrected with convex lens [+powered]). Myopia: Eye is too long, focal plane lies before retina: the person is nearsighted and sees distant objects as blurred (corrected with concave lens [-powered]). 89 Chapter 4 Our senses: Vision Problems with the eye Presbyopia: Type of farsightedness (like hyperopia) related to hardening/diminished elasticity of the lens as we get older (> 40 years). Corrected with reading glasses (+ powered convex lens) 90 30 8/23/2024 Chapter 4 Our senses: Vision Problems with the eye Astigmatism: Imperfections in the spherical curvature of the cornea or the lens results in multiple focal points (blurry vision at all distances). Can be corrected with a cylinder. 91 Chapter 4 Our senses: Vision Problems with the eye Cataract: clouding of the lens (age, diabetes) Macular degeneration: Retinal degeneration of the fovea. The focus is black and distorted Glaucoma: worsening/loss of peripheral vision (failure of nerve cells due to increased eye pressure) 92 Chapter 4 Our senses: Vision Retina Receptive fields of ganglion cells Retina Remember, compressed information from cones/rods is sent via bipolar cells to ganglion cells, who relay the information Receptive to the optic nerve. field of ganglion One ganglion cell receives input cell from multiple cones/rods Cones/rods 93 31 8/23/2024 Chapter 4 Our senses: Vision Receptive fields of ganglion cells are donut-like ON center cells Receptive field of ganglion cell OFF center cells 94 Chapter 4 Our senses: Vision Receptive fields of ganglion cells are donut-like 95 Chapter 4 Our senses: Vision ON center cells (also Center ON) - a closer look 1. 2. 3. - + - + - + high frequency firing Low frequency firing cell fires more rapidly than in 2. - Excitatory response from center increased relative light to inhibitory response from surround (i.e., less lateral inhibition from surround compared to 2.) 96 32 8/23/2024 Chapter 4 Our senses: Vision Receptive fields of ON center cells (also Center ON) can offer an explanation for some visual illusions. Hermann grid 1 2 1 - + - + 2 Receptive field 1 receives more surround inhibition - + than 2 (more light on surround = more inhibition - + = firing at slower rate than 2 → 1 is perceived as less intense than 2) The white bands are equally intense throughout, but grey circles appear at their intersections 97 Chapter 4 Our senses: Vision Receptive fields of ON center cells (also Center ON) can offer an explanation for some visual illusions. Mach bands 1 Receptive field 2 receives 1 - + more surround inhibition than 1 (more light on surround = 2 2 - + more inhibition = firing at slower rate than 1 → 3 - + perceived as less intense) Receptive field 3 receives less 4 - + surround inhibition than 4 (less light on surround = less inhibition = firing at faster The luminance is the same within one band, but rate than 4 → perceived as perceived luminance within a band varies. The more intense) contrast is exaggerated on the edges. 98 Chapter 4 Our senses: Vision The ganglion cells feed forward information to V1 (primary visual cortex) The nasal part of the optic nerve crosses at the optic chiasm(a), the temporal part continues on the ipsilateral (i.e. ‘same’) side. This results in a projection of the left visual field (not the left eye!) in the right hemisphere. The vast majority of the nerve fibers* in the optic tract project to the lateral geniculate nucleus (LGN) in the dorsal part of the thalamus (LGN is the main relay station in the pathway to the primary visual cortex). *About 10% of the optic nerve projects to the Superior Colliculus (to generate the next (reflexive) saccade [= rapid movement of the eye to change fixation point]). 99 33 8/23/2024 Chapter 4 Our senses: Vision From eyes to V1 – some problems Optic nerve is damaged/severed: all vision is lost in that eye lefteyeright Optic chiasm(a) is damaged/severed: outer part of the visual field is lost in both eyes lefteyeright Visual pathway from LGN to V1 is damaged/severed: visual field is lost in both eyes eye left right 100 Chapter 4 Our senses: Vision V1 (also primary visual cortex, striate cortex, calcarine cortex, Brodmann area 17) is the main site where input from the retina arrives. https://www.sciencedirect.com/topics/engineering/primary-visual-cortex 101 Chapter 4 Our senses: Vision V1 comprises 6 layers, information from LGN arrives in Layer 4. LGN is also layered*– main distinction is between parvocellular (input from small ganglion cells) versus magnocellular (input from large ganglion cells) that both project to layer 4 in V1. * layers 2, 3, and 5 receive input from the ipsilateral eye and layers 1, 4, and 6 receive input from the contralateral eye. 102 34 8/23/2024 Chapter 4 Our senses: Vision The ~100 million cells in V1 have a retinotopic organization (neighboring cells on retina project to neighboring cells in V1) and there is cortical magnification (80% of the cells in V1 receive input from macula). 103 Chapter 4 Our senses: Vision Cells in V1 selectively respond to lines with a particular orientation within specific retinal location (Hubel & Wiesel) Hubel and Wiesel Cat Experiment - YouTube 104 Chapter 4 Our senses: Vision After V1, cells project to V2, V3, V4, V5 (or MT) and other pathways. 2 main routes: - ventral pathway to temporal cortex (IT): WHAT (shape and identity of object) - dorsal pathway to parietal areas: (perceiving spatial relations, aiming, reaching) – originally viewed as WHERE pathway (Ungerleider & Mishkin, 1982), but HOW pathway seems to be more appropriate (Goodale, 1995) 105 35 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) 3 properties - Hue (which color? → wavelength) - Brightness/intensity (wave amplitude) - Saturation (complexity of light [range & # of different wavelengths]) 106 Chapter 4 Our senses: Vision Color perception (V4) Newton showed that white light is comprised of multiple (7) colors (violet, indigo, blue, green, yellow, orange, red). White light can be split into a spectrum of colors with a prism, and recombined through another prism 107 Chapter 4 Our senses: Vision Color perception (V4) Additive mixing: Red, green and blue light can be combined (wavelengths are added in the mix) Trichromatic theory (Young-Helmholtz): All colors can be obtained by mixing red- green-blue (the 3 primary colors) in different proportions (RGB color coding). 108 36 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) There are also 3 types of cones in the eye, more sensitive to either short (S), medium (M), or long (L) wavelength light S cones (~2% of cones in retina) respond most to blue spectrum (peak ~420 nm = violet) M cones (~33% of cones in retina) respond most to green-to-yellow spectrum (peak ~530 nm = yellowish green) L cones (majority of cones in retina) respond most to red spectrum (peak at ~560 nm = Rods (white curve) do not contribute to color perception, but are most sensitive to medium wavelengths. yellow) Every color in the spectrum provides a unique activation pattern across the three types of cones. The combined (summed) activity of the three cone types is the foundation of color perception. 109 Chapter 4 Our senses: Vision Color perception (V4) 110 Chapter 4 Our senses: Vision Color perception (V4) There are also 3 types of cones in the eye, more sensitive to either short (S), medium (M), or long (L) wavelength light Some examples: - White light: all cone-types are activated equally (rods are also activated) - Yellow light: M-cones and L-cones are activated, S-cones are not - Orange light: M-cones (slightly) and L-cones activated, S-cones are not - Cyan light: S-cones and M-cones activated, L-cones are not 111 37 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) Subtractive mixing: mixing colored ink, paint etc. (wavelengths are removed in the mix). CMYK color model (cyan, Well-known model based on Blue, Red and magenta, yellow, key [black]): Yellow as primary colors (because these color coding model based on cannot be obtained by mixing other paint subtractive mixing (printers) colors) is also a subtractive model. 112 Chapter 4 Our senses: Vision Color perception (V4) Subtractive mixing. Blue paint is blue because light with a wavelength in the ‘blue’ range is reflected. Yellow paint is yellow because light in the ‘yellow’ range is reflected. mix wavelengths in ‘yellow’ spectrum absorbed by blue paint wavelengths in ‘blue’ spectrum absorbed by yellow paint wavelengths reflected by both blue and yellow paint adapted from Sekuler and Balke (2002) 113 Chapter 4 Our senses: Vision Color perception (V4) Color coding in the retina Most parvocellular (small) ganglion cells are sensitive to differences in wavelengths, which is reflected in their receptive fields. -+ +- -+ -+ +- 114 38 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) Color coding in the retina Most parvocellular (small) ganglion cells are sensitive to differences in wavelengths, which is reflected in their receptive fields. Examples Red CenterON/Green surroundOFF Blue CenterON/Yellow surroundOFF Retina Retina - + - + The combination of ‘green’ and Receptive field of ganglion cell ‘red’ cones in the surround can Cone type (‘red’, ‘green’, ’blue) encode ‘yellow’. 115 Chapter 4 Our senses: Vision Color perception (V4) Color coding in the retina 116 Chapter 4 Our senses: Vision Color perception (V4) Opponent-process theory (Hering, 1878 an onwards): six primary colors organized in 3 pairs (red-green, blue-yellow, black-white). The opponents inhibit each other on ganglion-level, which leads to perception of achromatic (colorless) light. Versus Trichromatic theory (Young-von Helmholtz): All colors can be obtained by mixing red-green-blue (the 3 primary colors) in different proportions (RGB color coding). Theories seem to clash, but both explain color vision: - Trichromatic theory explains how different cone receptors detect different wavelengths at a receptor level. - Opponent process theory explains how cones connect to the ganglion cells and how wavelengths of light can drive opposing inhibitory/excitatory processes (the neural level). 117 39 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) Opponent-process theory explains red/green color blindness → the most frequent type of color blindness in which red/green hues cannot be distinguished (Males ~8%, Females ~1-2%) Ishihara test 12 should be 8? → fine Nothing? → fine visible to all 3? → red/green deficiency 2? → red/green deficiency 118 Chapter 4 Our senses: Vision Color perception (V4) Color-blindness often goes unnoticed: - Unaffected colors can be discriminated just fine - Lightness can be a cue for color - The label attached to a color can be correct, even though it may not be precisely discriminated - Knowledge about the world (e.g., when the spatial layout of a traffic light is understood, perceiving the correct color is not necessary) normal red/green blue/yellow monochromatic vision deficiency deficiency vision 119 Chapter 4 Our senses: Vision Color perception (V4) The opponent processing theory can explain negative color afterimages Look for 30 s afterimage Basic idea: A part of the retina is subjected to green. The M-cones in that area receive more stimulation than the S- or L-cones, and the area becomes desensitized. The mixed wavelengths of the white surface then produce a stronger output from the S- and L-cones relative to the rest of the retina. 120 40 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) The ‘classic’ color-afterimage effect is specific for the retinal position and eye. 121 Chapter 4 Our senses: Vision Color perception (V4) However, the afterimage can spread to areas that were not actually colored in the image that a person is adapting to (Shimojo et al., 2001). (One of the possible) afterimages Center is white but appears blueish (perceptual filling) Color afterimages can thus not solely be explained by the retina/eyes, and adaptation of the cortex also seems to play a role. 122 Chapter 4 Our senses: Vision “Hey there, what’s so special about dogs anyway? We also Color perception (V4) have a tapetum lucidum!” Burning questions: Can my dog see colors? Yes, but dogs only have two types of cones and cannot distinguish red/green (the red-green system is phylogenetically the youngest). Dogs have more rods than humans though (good for night vision and detecting movement), and have a reflective lining on their retina (tapetum lucidum). Light that does not get absorbed by the photon receptors thus gets a ‘second chance’ of being absorbed, but this slightly blurs the image. Dog’s view Dog’s view (no red in frisbee & blurry) (blurry, but blue toy is fine) 123 41 8/23/2024 Chapter 4 Our senses: Vision Color perception (V4) Burning questions: Why can’t I see colors at night? Cones need light with high intensity. At night, only rods are used (remember: rods are colorblind). Since the fovea is packed with cones fixating next to an object at night (rather than fixating directly on the object) makes it clearer. What does it mean that my eyes ‘have to adapt to the dark’? After photons hit rods, the cells needs to recover (rods saturate more easily than cones), which can take about half an hour (when going from bright sunlight to complete darkness). But, after that, rods become very sensitive. - About 9 photons are required at the receptor level to detect a light source. These photons are spread over many rods, so a rod must be capable of detecting a single photon. 124 Chapter 4 Our senses: Vision Color perception (V4) Burning questions: How many colors can I see? That depends on the task. We might see > 1 million different hues when presented simultaneously, but not when presented successively. Our memory/percept for color strongly depends on the labeling (categorical perception). English has 11 focal color names (black, white, red, green, blue, yellow, brown, purple, pink, orange, grey). People who have languages with fewer color names don’t have different visual system, but just label things differently. It appears that we mostly remember the color name, not the color itself. 125 Chapter 4 Our senses: Vision The visual brain: Perception Sensation: awareness of stimulus due to stimulation of a sense organ Perception: organization, identification and interpretation of a sensation to form mental representations This difference becomes clear in patients with visual form agnosia. - Sensation is just fine (patients are not blind) - But objects cannot be recognized (‘What is this?’ cannot be answered) - Patients with apperceptive agnosia can also not copy a line drawing (and are better when asked to draw from memory) 126 42 8/23/2024 Chapter 4 Our senses: Vision The visual brain: Perception We’ve already seen that the visual system is highly tuned to edges (e.g., the contrast illusions explained via receptive fields of ganglion cells), orientation (e.g., neurons in V1 fire in response to lines with a specific orientation), color (etc). But we perceive complex objects (like cars, faces, animals) rather than individual features. As noted, Gestalt psychologists were the first to focus on this. 127 Chapter 4 Our senses: Vision The visual brain: Perception Gestalt psychologists discovered many principles of perceptual grouping 128 Chapter 4 Our senses: Vision The visual brain: Perception Simplicity: We perceive the simplest shape possible, even when it is made up of several different shapes (triangle + rectangle) 129 43 8/23/2024 Chapter 4 Our senses: Vision The visual brain: Perception Closure: We fill in missing elements (edges that are separated by gaps are perceived as as belonging to one object) 130 Chapter 4 Our senses: Vision The visual brain: Perception Continuity: Edges or contours with similar orientation provide ‘good continuation’ 131 Chapter 4 O
