Cognitive Psychology Flashcards
What is cognition?
- The mental action or process of acquiring knowledge and understanding through thought, experience, and the senses
- Refers to all of the thoughts and experiences that happen within our mind
- Scientific study of thought and experience
What is the information-processing approach? (schedule)
Stimulus (something in the outside world, e.g. noise) ->
Attention ->
Perception ->
Thought processes ->
Decision ->
Response of action
- Happens sequentially in order, one module to the next (e.g. hearing a lion roar and then making the decision to run away)
- Humans as “stimulus response machines” - something happens in the outside world, we process it, and then respond
- Information comes in through the senses
- It’s processed by a series of modules that change the information in a systematic way
- The output of these processing modules ultimately causes an observable response
Explain serial processing versus bottom-up processing
Serial processing - only one step at a time
Bottom-up processing - all processes are directly triggered by the stimulus
What are criticisms of the information-processing approach?
- It doesn’t allow for parallel processing (e.g. multitasking)
- It ignores top-down processing (processing that is caused by the individual’s mind, brain, prior knowledge, goals, expectations, etc.) (applying your own knowledge of the world to change the way you perceive something)
- It’s an oversimplification!
Bottom-up processing: representations in our heads (give an example)
- All our thoughts are perceptions come from our brain, so everything we see and experience in the world is also in our brain (represented in our brain)
Example:
- Person is looking at a scene with a dog in it
- This person has an experience of seeing a dog, so that person will have a representation of a dog in their brain
- The brain is made up of millions of brain cells
- The firing of all of those neurons/brain cells, produces/represents the dog
- Your conscious experience of what’s happening in the world/anything in front of you (e.g. a pen), the representation of the pen when you look at it is in your brain somewhere - there are neurons that are firing and those neurons firing together is your experience of the pen
- If you can have a thoughts about it, then ‘it’ exists in your neurons (e.g. a snapchat is represented on your phone as zeros and ones, despite the fact that it looks like something meaningful to you)
- So too, that snapchat image is represented in your head by activity of a large number of neurons, despite the fact that it looks and feels like something meaningful to you
How could neurons represent complex information?
- Some neurons have “preferred” stimuli (e.g. respond to a certain orientation, colour, or even complex concept like Luke Skywalker or Jennifer Aniston) (stimuli that will cause them to fire more often than with other stimuli)
- Something referred to as “Grandmother cells” (idea that there is a neuron in your mind that fires when you think about your grandmother)
- Electrodes implanted in the medial temporal cortex of patients who were having epilepsy surgery - could be used as an opportunity for cog scientists to record info from these neurons to better understand how this works and how neurons functioned
- Showed this particular individual lots of stimuli (pictures, words, sounds), and looked at how often their neurons fired
- Lots of neurons fired when shown pictures of Luke Skywalker or Mark Hamill, when shown the name Luke Skywalker, when hearing someone say Luke Skywalker, etc.
- However, didn’t fire very much to other stimuli (e.g. picture of Leonardo DiCaprio, the name Emma Thompson)
- That neuron, in some way, represents Luke Skywalker in the brain of that patient
- Doesn’t represent anything physical about Luke Skywalker (still fires when looking at a picture of him, a picture of his name, someone saying his name), also fires a fair amount when shown a picture of Yoda (that neuron isn’t representing physical aspects of Luke Skywalker, or Yoda, that neuron is representing Star Wars (or at least Luke Skywalker and his role in it)
- Not necessarily the only neuron that would fire to Luke Skywalker - is probably part of a big network of lots of groups of neurons where some represent Luke Skywalker, some represent Yoda, some represent Star Wars (it won’t be an individual neuron that represents a concept, it’ll be a large number of them)
- Showing that there are neurons that care about particular concepts and not about physical features
Explain rate codes versus temporal codes
Rate coding - greater rate of a neuron’s response is used to code/represent information
Temporal coding - greater synchrony (same time) of the responses of several neurons is used to code information
Explain experimental cognitive psychology
- Studying behaviour in controlled lab settings
- Shed light onto cognitive processes by using clever experimental manipulations
- Traditionally, experiment psychology doesn’t care about the underlying brain processes
- Instead of “brain measures”, cognitive psychology uses behavioural measures like reaction time (RT) or accuracy as indirect measures
Explain the Stroop test, congruent stimulus, and incongruent stimulus
- You see a colour word (e.g. red) written on the screen, but the word is also written in a colour (e.g. green)
- Your job is to only respond to the colour the word is written in, not what the word is
- Congruent stimulus - the colour of the word is what’s written (e.g. the word ‘red’ written in the colour red)
- Incongruent stimulus - the colour doesn’t match the word (e.g. word ‘red’ written in the colour green)
- Important tool for identifying how cognitive processes work and what’s happening in our brains (if reading is automatic, it will interfere with colour naming and cause longer reaction times and more errors)
What are the strengths and weaknesses of experimental cognitive psychology?
+ Extremely successful at generating theories about cognition that can be tested in neuroscience
+ Has made a huge contribution to making psychology a more empirical science
- Ecological validity - can we generalise findings outside the lab?
- Face validity - only provides indirect measures of cognitive processes (do we know that we’re actually measuring the concept we care about)
- Do psychological concepts even exist - should be careful not to assume something exists just because we’ve given it a name
Explain cognitive neuropsychology
- Studying cognition in patient with brain injury (example - patients with damage to the parietal lobe become unable to orient attention to one side of space)
- Goal is to find which cognitive functions are impaired, and which ones are preserved when a given brain region is damaged
What are the weaknesses of cognitive neuropsychology?
- No baseline - we don’t know exactly what the patient could do before their injury
- Generalisation - lesions in some areas of the brain are relatively common, while others are very rare (if a patient is the only patient with damage to a particular area of the brain, how do we know we can generalise that?)
- Modularity (assumption that the brain is divided into these discreet models, e.g. where a certain part of the brain does language, a certain part of the brain does attention) - cognitive process X is likely distributed across multiple areas, not just one (the brain is probably more of a distributed system, e.g. you applying attention to something is likely to involve communication between multiple parts of your brain rather than just one part)
Explain cognitive neuroscience
- Relates brain structure and brain function to cognitive processes
- Typically done by recording brain activity while participants perform cognitive tasks
Provide statistics on the brain (e.g. how many neurons does it have, what percentage of neurons make up brain cells)
- The human brain has approximately 80 billion neurons
- Each neuron may connect with 10,000 other ones (you can get from any one neuron to any other in just 3 neurons)
- Neurons make up about 50% of brain cells (glia cells comprise rest)
Provide details on the brain (structure)
Lobes of the cerebrum
Positioning:
- Frontal lobe - front-middle of top of brain
- Parietal lobe - back-middle of top of brain
- Temporal lobe - bottom middle of brain
- Occipital lobe - back middle of brain
- Cerebellum - back bottom of brain
What tools are used to study the brain?
- Electrophysiology (EEG)
- Structural Imaging (MRI)
- Functional Imaging (fMRI)
- Brain stimulation (TMS)
Explain electrophysiology, and when it is justified
- Very small electrode records neural activity from within axon (intracellular) or from outside axon membrane (extracellular)
- Usually only obtained from animals
When is it justified?
- Have the rare chance of recording from patients with epilepsy
- Sit in the hospital for weeks with the electrodes in their brain, waiting to have a seizure in order to be able to identify where in the brain the problem is
- The patients will get involved in research where cognitive psychologists will show them stimuli or get them to perform cognitive tasks, and record what these cells are doing during this
Explain electroencephalography (EEG)
- Electrical activity of a large number of neurons all firing together, recorded via electrodes on the scalp
- Allows us to measure neural activity in essentially real-time (millisecond scale) (can record data as fast as a neuron can fire)
- From EEG, we can get ERP’s (event-related potentials)
Explain event-related potentials (ERP’s)
- Measure EEG response to the same stimulus/task over and over
- Average waveform to generate an “event-related potential” (ERP)
- Just like averaging reaction times to get a cleaner estimate of the “true” effect
- We can compare the ERP’s between different psychological conditions (e.g. attended versus unattended stimuli)
- Shows that information you’re paying attention to is processed differently to information you’re not paying attention to by 100 milliseconds after that information is available to your brain
- Attended and unattended information is processed differently at that speed
- We can use understanding of that speed to understand when in time different cognitive processes occur, to help us to test hypotheses and theories about how cognitive processes are represented and how they occur within the brain
What are the advantages and limitations of EEG/ERP (electroencephalography/event-related potentials)
+ Very good temporal resolution (milliseconds) (e.g. WHEN something happens)
+ Portable and relatively cheap
- Cheap spatial resolution (centimetres) (e.g. WHERE in the brain it happens; there are an infinite number of possible origins for any signal recorded at the scalp, so we need solid computational models to make an informed guess)
- We can understand when cognitive processes happen, but we don’t get a huge amount of information about which parts of the brain are responsible)
Explain Magnetic Resonance Imaging (MRI)
- Very strong magnetic field: 0.5-7 Tesla (T)
- 1 Tesla = 10,000 Gauss
- Magnetic field of the Earth = 0.5 Gauss
- So our scanner here is 60,000 times the magnetic field of the Earth
Explain the basic principles of MRI
- Single protons in water molecules tend to align to the powerful and stable magnetic field generated by the scanner
- We then disturb this alignment with short radio-frequency pulses and measure the resulting changes in magnetic field
- Different parts of the brain (grey matter, white matter, CSF) take different times to “relax” from the radio frequency disturbance, and show as lighter/darker
Explain structural MRI: diffusion tensor imaging
- DTI can image white matter fibres (bundles of axons) by measuring the direction of water diffusion
- Allows us to study how cognition/perception is supported by connections between brain regions
What does fMRI measure?
- BOLD = Blood Oxygenation Level Dependent signal
- Active neurons need oxygen
- The brain starts supplying oxygen to active areas, producing an “overshoot” in oxygenated blood
- Oxygenated blood causes less magnetic field disturbance than deoxygenated blood, so active brain regions will have higher signal
Explain subtraction logic using an example
- Research question: What regions of the brain are involved in successful memory retrieval?
- Task: participants study a list of words and then are visually presented with words individually on the screen and asked if it was studied or not (e.g. old or new)
What are the advantages and limitations of fMRI
+ Very good spatial resolution (millimetres) (e.g. WHERE something happens)
- Poor temporal resolution (seconds) (e.g. WHEN it happens)
- Not a measure of neurons themselves (requires an indirect interference that neurons are firing because that part of the brain is using more oxygen)
Explain brain stimulation techniques
- All the methods so far are purely correlational
- To know if a particular part of your brain is important for a cognitive process, we need to change the activity of that part of the brain and show that it changes behaviour (e.g. we need causal evidence, not just correlational)
Explain transcranial magnetic stimulation (TMS)
- Short magnetic pulses that briefly affect electrical activity in a localised patch of brain tissue under the coil
- Is typically applied either before or during a cognitive task
- Can have positive or negative effects on task performance
What are the advantages and limitations of brain stimulation?
+ Causal evidence that a particular region is important for a cognitive function (not just correlational, like brain imaging)
+ Mostly non-invasive (e.g. safe and painless for healthy populations)
What are the limitations of cognitive neuroscience?
- Expensive/invasive (often means that sample sizes are small; generalisable?)
- Theories (emphasis in the literature on measuring brain effects rather than testing theories)
- Does it help us understand cognition? (what does it mean to understand? Could a neuroscientist understand a microprocessor?)
What can we learn from illusions?
- The brain doesn’t see at all - it received electrical signals about light interacts with the eye, and then it must infer what is out there in the world
- Your cognitive abilities have limits
- Generally, you perceive what you expect to perceive
- Your sensory systems are imperfect and idiosyncratic (distinct, individual, different to everyone else) (your experience of an event will be different to how the person next to you experiences the event) (perception feels “richer” that it is)
- A lot happens between a “noisy” sensory input and your subjective perception
- Top-down processes have a strong influence on perception (perception isn’t veridical/reliable)
- Mental/cognitive processes have limits (your brain’s resources are finite and need to be distributed)
Do our cognitive abilities have limits?
- Yes!
- You aren’t as aware of the world as you think you are
- Implications for eyewitness testimony, driving safety, UX/UI design, etc.
Do expectations play a significant role in what you perceive?
- Yes!
- Implications for schizophrenia and depression
- Positive versus maladaptive thoughts - changes your impression of something (e.g. walking into a room thinking everyone likes you versus thinking everybody hates you)
- Cells are unable to process something that small, so only focuses on bigger changes
How do we get from photons to knowing so much about an object? (knowing the rest of the spoon handle is behind the teacup despite not being able to see it)
- We make that inference just from photons, which are bouncing off the surface in front of us and coming into our eyes and hitting our retinas
- There’s nothing physically in front of us that tells that there is indeed a spoon handle behind that coffee cup
- We’re just getting light from the screen, hitting our eyes, telling us that there’s an edge here (e.g. some light here, some darkness here, etc.)
Explain taking in information from the eye to the cortex
Reception (absorption of physical energy, e.g. photons) ->
Transduction (physical energy is converted into an electrochemical pattern in the neurons) ->
Coding (one-to-one correspondence between aspects of the physical stimulus and aspects of the resultant nervous system activity)
Explain the roles of rods and cones
Rods - vision in dim light and movement
Cones - colour vision, sharpness of vision
How many cones are there in the retina?
6 million (most in the fovea)
How many rods are there in the retina?
125 million (in the outer regions of the retina)
What is the fovea?
Where you’re looking, where your eye is pointing
Explain density, and where the cones and rods are distributed
How many cones there are at each of these angular separations from our fovea from where we’re looking, so how many cones and how many rods
- All of our cones are in the fovea (where your eye is pointing is where most of your cones are)
- The rods are primarily distributed in your periphery
Do cones or rods care about colour?
Cones - primarily care about processing colour
Rods - don’t care about colour
What range is the human eye most sensitive to?
Light in the green range
What is Trichromatic Theory?
- Young found that all colours of the spectrum can be produced by mixing 3 primary colours
- Von Helmholtz proposed that there must be three types of colour receptors in the human eye, responding to different wavelengths of light
The three types of colour receptors:
- One that really cares about red
- One that really cares about blue
- One that really cares about green
(Because the different amount of input to those red, blue and green could combine to give you all possible colours of light that you can perceive
The three types of cones that prefer different wavelengths:
- Short (blue)
- Medium (yellow-green)
- Long (red)
What is Opponent-Process Theory? (Hering)
- Sighted people will never perceive blueish-yellow or reddish-green, and also experience negative afterimages
- Colour perception assumed to have three opponent processes
- Dual-process theory (Hurvich & Jameson) linked these processes to combinations of inputs from the three cone types
- So trichromatic theory works at the level of photoreceptors, and opponent-process theory works at the level of neurons
What is Colour Constancy?
- The tendency for a surface to appear to have the same colour despite a change in the wavelengths contained in the illuminant (the light source)
- Evolutionarily very helpful (e.g. the colour of light from the sun changes across the day)
- So the colours of things will change across the day (e.g. fruits) and it’s important for us to know whether something is safe to eat at multiple times of the day (example)
- What sighted people perceive isn’t entirely driven by the wavelengths of light that hit the retina:
- What the cones know is different from what the person perceives
- Perception is a constructive process
What happens after the retina? (explain what the parvocellular pathway and magnocellular pathway are)
Parvocellular (P) pathway -> sensitive to colour and fine detail -> most input comes from cones
Magnocellular (M) pathway -> most sensitive to motion -> most input comes from rods
What is the pathway from the eye to the brain?
- Retina ->
- Optic nerve ->
- Optic chiasm ->
- Lateral Geniculate Nucleus (LGN) ->
- Cortical area V1
Chiasm (makes a shape of an ‘x’ on the diagram, comes from the Greek letter ‘chi’ meaning ‘x’)
LGN - part of the thalamus
Which side do signals come when trying to reach an area of the cortex?
Signals reaching the left visual cortex come from the left sides of the two retinas
Signals reaching the right visual cortex come from the right side of the two retinas
What is retinotopy?
Things that are near to each other in space are processed in cells that are physically near to one another (e.g. if a certain neuron has a receptive field in a certain part of space, the neuron next to it will have a receptive field just slightly shifted in space from it)
What is lateral inhibition?
A reduction of activity (inhibition) in one neuron that is caused by a neighbouring neuron
If one neuron is firing a lot because there’s lots of light happening (lots of interesting things happening in its receptive field), it can reduce the probability that the neurons next to it are firing (essentially reducing the probability that the space around it causes neurons to fire)
Useful for enhancing contrast at edges of objects
Explain receptive fields
Means that you have a neuron in your brain that it fires when something happens in a certain circle/part of your visual world, and it only fires when something happens there
Receptive fields aren’t just the properties of visual neurons, you also have them for auditory neurons (e.g. will only fire for sounds of particular pitches)
Explain the functions of the Lateral Geniculate Nucleus (LGN)
- Part of the thalamus - a subcortical relay for most of the brain’s sensory input and motor input
- Cells have a centre-surround receptive field (responds to differences in light across their receptive field, e.g. light in centre, dark in surround)
- Maintains a retinotopic map
- Correlates signal from the retina in space and time (“Is an object moving towards me?”, provides the early 3D representation of space for action)
Explain the functions of the Primary Visual Cortex (V1)
- Extracts basic information from the visual scene (e.g. edges, orientations, wavelength of light)
- Sends this information for later stages of processing of shape, colour, movement, etc.
- Maintains retinotopy
- Single-cell recordings by Hubel & Wiesel indicate that some cells respond to simple features (e.g. points of light) and others combine those features into more complex ones (e.g. adjacent points of light may combine into a line)
What would damage to the V1 cause?
- Leads to a clinical diagnosis of cortical blindness (patient can’t consciously report objects presented in this region of space)
What is blindsight? (and the reasoning behind this)
- Means patient is still able to make some visual discriminations in the “blind” area (e.g. orientation, movement direction)
- This because there are other routes from the eye to the brain
- The geniculostriate route may be specialised for conscious vision but other routes act unconsciously
- Filling-in of ‘blind’ regions similar to filling-in of normal blind spot
- Patients with damage in primary visual cortex of brain can tell where an object is but claim they can’t see it
What is within the striate (visual) area?
V1
What is within the prestriate (visual) area?
V2, V3, V3A, V4, V5/MT
What is within the non-visual cortical area?
Posterior parietal regions, PST, TEO, superior temporal sulcus (STS), inferotemporal region (IT)
Explain Functional Specialisation Theory (Zeki)
- Different parts of the visual cortex are specialised for different visual functions
- The visual system resembles a team of workers, each of whom works on their own to solve part of a complex problem
What are the four areas of Functional Specialisation Theory, and what is the function of each area?
- V1 and V2 - early stage of visual perception (e.g. shapes)
- V3 and V3A - responsive to form (especially of moving objects)
- V4 - responsive to colour
- V5/MT - responsive to visual motion
What is the central assumption made by Zeki (in regards to Functional Specialisation Theory)?
That colour, form and motion are processed in anatomically separate parts of the visual cortex
Explain the findings of Zeki et al.’s brain imaging (PET) study
- V4 more active for coloured than greyscale images -> specialised for colour
- V5 more active for moving dots compared with static dots -> specialised for motion
Why can’t patients with cortical achromatopsia see colour?
- Because of damage to V4 (the colour centre of the brain)
- But often also due to damage to V2 and V3
- V4 is involved in colour processing, but the link between colour processing and V4 isn’t perfect
What is implicit colour processing?
- Can be to the extent that patients with achromatopsia perceive colours for things that they know the colour of (e.g. have an experience of seeing a banana as yellow, because perhaps before their injury they were aware that bananas are yellow - so they might still experience it even if that colour information isn’t being processed by their brain)
- So there’s bottom-up and top-down influences on V4 happening at the same time
- So V4 is important for colour processing, but perhaps isn’t the only place in which colour processing happens in the brain
Explain V5/MT: the motion centre of the brain and what damage to this area leads to
- V5/MT is heavily involved in motion processing brain imaging studies of humans
- Brain damage to V5/MT leads to akinetopsia
Patient LM:
- Bilateral damage to V5/MT
- Was good at locating stationary objects
- Had good colour vision
- Motion perception was grossly deficient
Explain the binding problem (a challenge for functional specialisation)
- Sighted people don’t perceive the colour of things separately to their shape, but in your brain those things are processed separately…so where in the brain is the thing that is perceived?
- How are the different features bound together to enable coherent object processing?
- Possible solution: coherent perception depends on synchronised neural activity between brain regions, which most likely depends on attention
Explain the where pathway and what pathway (two important visual pathways)
- Where pathway - parietal (or dorsal) processing pathway - concerned with movement processing - “vision for action”
(Found at the top back of brain) - What pathway - temporal (or ventral) processing pathway - concerned with colour and form processing - “vision for perception”
(Found at the bottom back of brain)
Vison for perception/vision for action
- Patient DF has a lesion to her lateral occipital cortex; she has trouble locating and identifying objects
- However, her conscious perception entirely different from the information that is available to her motor system - she has where but not what
Explain the neuropsychology of object perception
- Damage to parietal/occipital lobe? removes conscious visual perception
- Damage to parietal lobe? affects visual feature segregation and grouping
- Damage to temporal lobe affects knowledge of what an object is/is for
- Consistent with a hierarchical, multi-stage process
Are faces special?
- We don’t know, but probably
- There is evidence that faces are processed more holistically than other objects
- Evidence for face-specific brain regions (e.g. FFA), though this could be a visual expertise region too…
- After brain injury, some patients appear to have impairment in face but object recognition (e.g. prosopagnosia), suggesting that faces are special
What is the problem with faces?
- Face recognition is a within-category discrimination (all faces look very similar) (features of faces are processed and subsequently remembered less than for other types of objects, such as houses)
- Other object recognition is between-category (e.g. distinguishing a pen from a cup)
- Maybe faces require different types of processing to other objects?
- Faces are so important from a social/evolutionary perspective that they mat have a mechanism all to themselves?
What is the neuropsychological evidence that faces are special?
Prosopagnosia
- Prosop = “face” + agnosia = “without knowledge)
-> Impairment of face processing that doesn’t come from damage to early visual processing
- De Renzi - Patient failed to recognise his own family but could do so by voice or clothes (“I guess you are my wife because there are no other women at home”)
- Could match different views of faces and name other objects
-> Impairment at the stage of matching to stored information
Fusiform Face Area (Gauthier)
- Part of the ventral (what) stream
- Responds to faces more than other types of objects in functional imaging experiments
- Faces are special because we have become experts at within-category discriminations
Explain holistic processing in face recognition
- Sighted people are slower and less accurate at identifying inverted (upside down) faces
- Typically interpreted as evidence of holistic processing
- Qualitative differences in processing of upright and inverted faces? (e.g. spatial relational (holistic/configural) information is disproportionately affected by inversion, and therefore face recognition suffers)
Explain the different sections of a model of object recognition
- Early visual processing (colour, motion, edges, etc.)
- Perceptual segregation - grouping of visual elements (Gestalt principles, figure-ground segmentation)
- Matching grouped visual description onto a representation of the object stored in the brain (called structural descriptions)
- Attached meaning to the object (based on prior semantic knowledge)
Explain perceptual organisation through perceptual segregation and Gestalt Psychology
Perceptual segregation:
- Separating visual input into individual objects
- Thought to occur before object recognition
Gestalt Psychology
- Fundamental principle: the “Law of Pragnanz”
- Assumes a set of rules that operate early in visual processing
What are some weaknesses of Gestalt’s Psychology?
- Most evidence only descriptive, not explanatory
- Relies heavily on introspection and evidence from 2D drawings
- Some segmentation clearly occurs via top-down prior knowledge
Segmentation processes aren’t always bottom-up and following the laws of perceptual organisation
- Task of the pp’s was to push a button to say whether the two x’s were on the same object or not
- Participants were found to be quicker on the top objects, which are letters whereas the bottom ones aren’t
- You know the shape of the objects on the top (letters), whereas the shape of the objects on the bottom are unfamiliar
Explain object recognition deficits
- Agnosia - impairment in object recognition (without primary visual deficits)
- Different kinds of impairments should arise depending on the stage at which object recognition is damaged
Explain the two types of agnosia, using case studies
Apperceptive agnosia
- Impairment in the process which constructs a perceptual representation from vision (e.g. grouping)
- Seeing the parts but not the whole
- Associated with lateral occipital lobe damage
(e.g. Patient HJA bad bilateral ventral-medial occipital damage; could recognise objects from touch but a marked impairment in visual object recognition (e.g. line drawings over silhouettes); had problems grouping or organising information (e.g. recognising any objects presented together with other objects, such as a paintbrush - saw the bristle and handle as two separate objects rather than one))
Associative agnosia
- Impairment in the process which maps a perceptual representation onto knowledge of the objects functions and associations
- Seeing the whole but not its meaning
- Associated with occipito-temporal damage
- Visual object agnosia - one of several varieties of associative agnosia
- Patient LH (left) - preserved ability to copy drawings of objects, but unable to name them or show what they are for (no access of semantics); damage to occipito-temporal regions
What is importance of culture on object perception?
- Most psychology research comes from white male Western researchers and participants
- Westerners prioritise processing/categorising objects, while East Asians prioritise the relationships between objects and context
- Less activation of “object perception” regions in East Asians than Westerners during scene viewing
- Never assume that psychological “truths” apply to all of humanity
What are criticisms of visual expertise?
- Not all prosopagnosic patients are impaired on within-category discrimination
- Patient WJ - owned a flock of sheep and could distinguish between them
- Patient RM - could distinguish between his collection of 5000 miniature cars, but was unable to identify famous faces or his own and his wife’s face
Why does this image (blue lines) produce illusory yellow?
Need to work out at some point by watching what’s said in lecture recording
Define attention
- “The taking possession by the mind, in clear and vivid form, of one out of what may seem several simultaneously possible objects or trains of thought” - William James
What are the paradigms to study the limits of attention?
- Inattentional blindness
- Change blindness
- Attentional blink
What is inattentional blindness?
- We overestimate how much of the world we are actually aware of
- Even very salient (attention-capturing) things can be missed
Explain the original gorilla study (Simon & Chabris)
- Transparent/Umbrella
- Transparent/Gorilla
- Opaque/Umbrella
- Opaque/Gorilla
Two video styles:
- Transparent: white team, black team, and unexpected event all filmed separately and superimposed onto each other
- Opaque: white team, black team, and unexpected event all filmed simultaneously, so people and objects can be occluded (blocked)
Two counting conditions:
- Easy: count overall number of passes of your team
- Hard: count aerial and bounce passes of your team separately
Results:
Higher percentage monkey seen in opaque conditions (opaque easy task, opaque hard task, transparent easy task, transparent hard task)
Conclusion:
- Inattentional blindness can be induced easily in healthy participants
- It occurs more frequently if the display is transparent
- Depends on the difficulty of the task: the more the primary task occupies attention, the less likely they are to see the gorilla/umbrella
- So attention is a limited resource that you distribute
Explain Central Capacity Theory (Kahneman)
- A single central capacity (e.g. central executive; attention) that can be used flexibly
- Strictly limited resources
- Single pool shared between competing tasks
- Dual task costs will emerge when two tasks exceed the total resource available
- An experimental approach: Participants talking on a hands-free mobile phone while driving in the simulator
What is the attentional blink? (Raymond & Shapiro)
- We can make something invisible by showing it to people very quickly after showing them something else that is important to them
Key ingredients:
- Rapid visual stimuli (at ~ 10 Hz)
- Pp’s asked to look out for TWO targets and report if they saw them at the end of each trial
- The first target is referred to as T1, and the second target as T2
- Masks/distractors need to follow T1 and T2 for the effect to work
Explain event-related potential
- When your brain accesses the meaning of almost any stimulus (a word, picture, sound), we see a negative event-related potential (N400)
- N400 reflects cognitive processes related to accessing the meaning (semantics) of a stimulus
- If T2 is a meaningful word, does your brain process its meaning at all?
- We can use the N4000 as a sign./marker that someone’s brain is processing meaning, without them telling us their behaviour
Luck et al.:
- Classic AB to T2 - e.g. the word ‘cat’ is less likely to be seen when shown 300ms after T1
- BUT the N400 is pretty much the same size regardless of time since T1
- Therefore, even if you don’t know that you saw T2, your brain still did some processing what it means
Explain Interference Theory (Shapiro) (theories of the attentional blink)
- T1, T2 and their masks/distractors are all encoded into a temporal buffer (e.g. visual short-term memory)
- The AB is competition for retrieval among all items in short-term memory
Isaak:
- Reported that the AB increases with increasing number of task-irrelevant competitors/distractors
A unified model:
- Due to the mask following T1, increased attention is required to process T1
- This leaves less attention for processing of T2, which leaves T2 vulnerable to decay or interference from distractors
Explain the Cocktail Party Problem
Dichotic listening tasks (Cherry)
- Unattended auditory information is processed to a lower level of complexity than attended information
- 1/3 of participants report hearing their name in the unattended channel
- Easier if voices are physically different (bottom-up processing)
Johnsrude:
- A familiar voice is easier to pay attention to AND easier to ignore
- We use our own experiences of the world to help to solve the cocktail party problem (top-down processing)
- Target = voice to attend to
- Masker = voice to ignore
- Novel baseline = both unfamiliar voices
- X-axis shows volume of target relative to masker
Explain Broadbent’s Theory (attention as early selection)
- Parallel input into sensory register
- Inputs are then filtered on the basis of its physical characteristics
- Filtering prevents overloading of the limited capacity mechanism
- Inputs remaining in the buffer after filter are available for later (semantic) processing
- Accounts for Cherry’s basic findings (unattended stimuli only undergo minimal processing before being filtered)
- Accounts for findings from dichotic listening task (filter selects an input on the basis of the most prominent physical characteristic distinguishing the inputs)
- BUT
- At least some parts of the unattended stream are processed semantically (e.g. hearing your name within a conversation you’re not paying attention to)
- Stimuli that people don’t report ever experiencing can still change their behaviour (e.g. blindsight from last week)
Explain attention as late selection (Deutsch and Deutsch)
- All stimuli are fully analysed
- The bottleneck occurs late, before the response
- The most relevant stimulus determined what response is made
- But, early sensory event-related potentials (~ 100ms post-stimulus) are smaller if unattended
- Places the bottleneck much earlier during processing
- Results favour Treisman’s perspective
Explain attention as flexible selection (Treisman’s Leaky Filter)
- Unattended information is attenuated/filtered after the sensory register
- Stimulus analysis proceeds through a hierarchy from physical characteristics of the stimulus up to its meaning and beyond
- When capacity is reached, tests at the top of the hierarchy are precluded for all but the ‘attended’ stimulus
- Precise location of the bottleneck is more flexible than in Broadbent’s model
(looking at images of all three theories will make them easier to understand)
When is attention selection happening?
- Initially, the field considered a distinction between early (e.g. Broadbent) and late (e.g. Deutsch & Deutsch) selection
- In reality, it’s probably flexible and influenced by many top-down and bottom-up processes
Explain the Posner Cueing Paradigm (covert attention)
- Sighted people can pay attention to a part of space that they aren’t directly looking at (called “covert attention”)
Typical results:
- Endogenous attention - choosing to pay attention to a particular part of space makes you react faster to things that happen in that part of space
- Exogenous attention - the same is true of your attention being drawn to that part of space without you intending to, BUT ONLY if the something happens in that part of space very quickly after you shift your attention to it
- So, two different systems with different functions
Explain Posner’s Attentional Systems
Endogenous System:
- Controlled by the individual’s intentions and expectations
- Involved when central cues are presented
- Top-down
(1/4 front top of brain)
Exogenous System:
- Automatically shifts attention
- Involved when uninformative peripheral cues are presented
- Stimuli that are salient or that differ from other stimuli are most likely to be attended
- Bottom-up
(3/4 back middle of brain)
Explain visual search using the example of Where’s Wally
- Searching a cluttered visual environment for task-relevant information is difficult
- When Wally (target) shared one or more features with other things in the image (distractors) (e.g. red white stripes) it’s even processed
Compare feature search and conjunction search in visual search paradigms
- Feature search - target has a unique feature that isn’t shared by other items in the display, and therefore “pops out”
(e.g. red A amongst blue A’s) - Conjunction search - target has no unique feature that isn’t shared by other items in the display, making visual search more difficult
(e.g. red A amongst blue A’s and red H’s)
Explain Feature Integration Theory (FIT) (Treisman)
- Perceptual features are encoded in parallel and prior to attention
- If an object has a unique perceptual feature, then it may be detected without the need for attention (“pop out”)
- If an object shares features with other objects, then it can’t be detected from a single perceptual feature and spatial attention is needed to search all candidates serially
- In other words, an object is only an object if you pay attention to it
What are the stages of visual search?
- Rapid initial parallel process to identify features (attention-independent)
- Next, a slow serial process to form objects by combining features (focused visual attention binds the features into an object; feature combination can be influenced by prior knowledge, e.g. bananas are yellow)
Object in front of you -> pre-attentive processing of visual features -> focused attention to bind features -> perception of object
In what situations can illusory conjunctions of features occur?
- When focused attention is absent (e.g. very brief presentations, or presentation outside focus on attention)
- When relevant stored knowledge is absent
- When spatial attention is diverted
- When display is presented in peripheral vision
Illusory conjunctions aren’t just guessing!
- They can occur with high confidence
- They don’t occur under all circumstances that decrease performance
- Illusory conjunctions happen across space but not time!
(e.g. when the two stimuli are presented at the same location across time, subjects don’t commit conjunction errors)
What evidence is there against Feature Integration Theory?
- Argues that an object is an object if it’s attended to
However, negative priming tasks (e.g. Tipper) show semantic (meaning) processing of unattended stimuli
What are the strengths and weaknesses of Feature Integration Theory?
Strengths:
- An important contribution to explaining what happens within the attentional spotlight
- Influenced thinking on a variety of topics from early sensory encoding to later attentional control
Weaknesses:
- Doesn’t explain why the similarity of distractors is influntial
- Neglect/extinction patients have problems with both conjunctive and single-feature targets
Explain Guided Search Theory/Dual Path Model (Wolfe)
- In real world search, people usually have expectations of where to find certain things
- Prior knowledge can make search more efficient
- Ehinger - found that observers fixate (look at) relevant parts of scene very early on
- Wolfe assumes a simultaneous mix of serial and parallel strategies for visual search, whereas in FIT processing moves from parallel (pre-attentive) to serial (attentive)
Early pre-attentive processes produce an activation map, where each item in the display has its own level of activation (according to how “promising” it is) (object with the greatest activation receives attention first) - Combines top-down and bottom-up processing for efficient search
Explain the procedure of our attentional blink experiment
Procedure:
- Each pp completed 20 trials altogether
- On each trial, 21 random letters were presented at a rate of 10 Hz
- The 7th letter in the stream was red - we call this T1
- The letter ‘x’ occurred after T1 on half of the trials - we call this T2
Participants:
- Undergraduate students
- All students participated in the same experiment
- Sample size - 288 pp’s
Task:
- Each pp completed 2 tasks: a dual detection task and a single detection task
Dual detection task
- Pp’s were told: “After each trial, you’ll be asked: 1) what letter was written in red, and 2) whether you saw the letter ‘x’” (e.g. they had to detect both T1 AND T2)
Single detection task
- Pp’s were told: “Ignore the red letters and just try to detect whether there is an X or not” (e.g. they ONLY had to detect T2)
(10 trials per task for a total of 20 trials)
Position of T2 relative to T1:
- In half of the trials, T2 occurred 300 ms after T1 (e.g. lag 3/short delay)
- In half of the trials, T2 occurred 700 ms after T1 (e.g. lag 7/long delay)
Explain the results of our attentional blink experiment
Single detection task:
- Short lag = 90
- Long lag = 93
Dual detection task:
- Short lag = 30
- Long lag = 67
Explain Balint’s Syndrome, using Treisman’s Patient RM example
- Two strokes damaging large areas of bilateral occipito-parietal cortex
- Simultanagnosia - unable to focus attention on more that one object at a time
- Problems combining features of a stimulus (made conjunction errors even when seeing objects for 10 seconds)
- Parietal lobe (“where” pathway) is important for feature binding
Explain the parietal cortex and feature bindings using Corbetta’s research
- During conjunction search, the posterior temporal cortex and parietal cortex show increased activation over baseline control conditions
- Walsh - transcranial magnetic stimulation (TMS) performed to parietal lobe disru0pts conjunction search, but not feature search
- Esterman - stimulation of intraparietal sulcus reduces illusory conjunctions
Define hemispatial neglect
A lack of awareness of stimuli presented to the side of space on the opposite side to the brain damage (contralesional)
Contralesion - opposite side of the damage
- “contra” - opposite
- “lesion” - damage
Explain the symptoms of hemispatial neglect
Cancellation task:
- Patient with hemispatial neglect given a piece of paper with individual lines on it and instructed to draw a line through each of them to turn them into crosses
- Found they ignored the lines on the left-hand side of the paper, as they weren’t aware of these lines
Line bisection:
- Patient with hemispatial neglect given a piece of paper with a horizontal line on it and instructed to draw a vertical line through the middle of it
- Found that they drew the line slightly to the right, as they weren’t aware that the line continued a bit onto the left-hand side
Copying:
- Patient with hemispatial neglect asked to copy line drawings
- Found that they were aware of what was one the left-hand side of the drawing (e.g. missing the numbers on the left-hand side of the clock, missing the windows on the left hand-side of the house, missing the left-hand side of the cat)
- Lack of awareness of things happening on the contralesional side of space - typically the left because usually neglect comes from damage to the right parietal lobe
Explain Bisiach and Luzzatti’s research
- Two patients with neglect were asked to imagine and describe the Piazza del duomo in Milan
- Both reported primarily the objects on the shared side of space (e.g. they had representational neglect)
- Had two patients who would spend lots of time in the square outside the duomo in Milan
- After their injury, thy were asked to imagine they were sitting at the steps of the cathedral in the square and describe what they saw
- Found patients generally never described anything that was one the contralesional side of space - so primarily described things on the right-hand side
- Then asked them to imagine they were sitting on the other side of the square (facing where they were previously sitting) and asked them to describe what they saw
- Found they described only things that were on the right-hand side of the square from their point of view (as if they have neglect for things in their mind’s eye)
Deficit to attend to information in contralesional space (patients have neglect for…)
- External sensory information
- Information in the “mind’s eye” (representational neglect)
- Bodily space (e.g. neglect to shave the other side of their face)
Explain unilateral neglect
- Often object-based irrespective of the object’s position in space
- Example: ignoring the left-hand side of all objects (e.g. tree, house), rather than only the objects on the left-hand side
- Unilateral neglect - “one side”, neglect to just one side
Explain extinction versus neglect
First trial:
- Ask a patient with extinction what they see and you flash the frog quickly so it’s in their left visual field
- Patients with extinction with say “I can see a frog”
- Patient with neglect won’t necessarily report that, because it’s on the contralesional side of space
Middle trial:
- Where you flash the sun on the right-hand side
- Extinction patients - “I can see the sun”
- Neglect patients - “I can see the sun
Final trial:
- Briefly flash the frog and the sun (frog on the left-hand side of space, sun on the right-hand side of space)
- Extinction patients - will only report seeing the thing on the ipsilesional side of space (“ipsi” - the same, the same side as the injury), so they will just report that they saw the sun and will have no awareness that a frog was also presented (can experience them, but only when they’re presented on their own; if there’s competition (one object on left and one on right), one on right seems to win (one on ipsilesional side wins and one on contralesional side loses)
- Suggest maybe attention is actually something that just appears (outcome of the fact that there are multiple representations in the visual world and they’re all competing
Explain extinction
- Often found in patients suffering from neglect, but can occur independently
- Patients detect a single stimulus presented to one visual field (typically left), but fail to detect the same stimulus when another stimulus is simultaneously presented to the other field
What is impaired in neglect?
- Neglect patients benefit from valid endogenous (originating from the body) cues in both visual fields
- Experiment in which cue on the right (intact) field predicted stimulus on the left
- Patients benefits as much as healthy controls from valid cue
- Both studies suggests that endogenous orienting system is relatively intact in neglect patients
Explain disengagement of attention
- Neglect patients most impaired when trying to disengage attention from intact side
- Attended hemisphere exerts a “hold” signal
- The invalid target should engage the exogenous (originating outside the body) system, but it doesn’t
