Perception Flashcards
What was the assumption about mind and body until the mid 1800’s?
an assumption that the mind and the body are separate from each other
What did Gustav Fechner reveal about the mind and body in the 1850’s?
the mind and body are not independent and so the mind can be studies by measuring the relationship between changes in physical stimulation and a person’s experience
What was proposed in ‘elements of psychophysics’, published in 1860 by Fechner?
proposed a number of methods to study the relationship between mental and physical. this included the proposal of three techniques to measure thresholds
Define Psychophysics:
the scientific study of relationship between physical stimulus and perceptions evoked by it
Define Absolute Thresholds:
measures the minimum of a stimulus that can be perceived by one of our senses
Define Difference Thresholds:
measures the smallest difference between two stimuli a person can detect
What is the steps of psychophysics deconstructed?
-physical stimulus (how do we select and present the stimulus)
-task (what does the participant have to do)
-measure (how do we categorise behaviour)
What are the three methods to measure thresholds?
method of limits, method of adjustment, method of constant stimuli
How is the threshold determined in the Method of Limits?
experimenter presents stimuli in ascending or descending order and determines the cross over point where perception changes. the threshold is the average of the cross over points
How is the method of adjustment carried out and how effective is the method?
the participant adjusts the stimulus intensity. It is a relatively fast method but it is frowned upon for it’s accuracy
What is the most accurate method of measuring threshold and why?
Method of constant stimuli because it involves more observations and the stimulus is presented in a random order to reduce order and expectation effects.
Describe the method of constant stimuli and how the threshold is reached:
the experimenter is presented stimuli of different intensities in a random order. participants indicate their perception, the stimulus is chosen so that the weakest is never detected and the strongest is always detected. The threshold is the intensity at which stimulus is detected 50% of times
How many intensities are typically involved in the method of constant stimuli?
5 to 9
What is a quick solution to the expectations of subjects and order effect?
Forced Choice Procedures (Fechner)
What do Forced Choice Procedures entail and how is the threshold determined?
stimulus is presented side by side and participants choose which side contains the stimulus (ie. grating) until it is too faint to see. Due to the guessing chance, if participants are unable to see the grating at all they should obtain 50% correctly. The Threshold is therefore determined at 75% correct
Explain the difference between 2AFC and 2IFC in the Forced Choice Procedure:
2AFC: the stimulus is presented at the same time
2IFC: the stimulus is presented one after another
What is the up-down method that measures perception?
Adaptive Staircase Procedure
How is the Adaptive Staircase Procedure carried out and how is the threshold reached?
intensities that are included in the threshold are presented. the procedure begins with perceivable stimulus and if correctly identified the intensity is decreased until an error occurs and the intensity is increased again. The threshold is determined by averaging over the transition and reversal points
What are three classical psychophysical tasks used to determine thresholds?
-detection: is the stimulus there?
-discrimination: which stimulus is stronger?
-matching: adjust the stimuli so they look/sound/feel the same
What is weber’s Law?
The ratio between the difference threshold and the intensity of the standard is constant
What does the difference threshold depend on?
the size of the standard stimulus
What is the accuracy of Weber’s Law determined by?
As long as the stimulus intensity is not too close to the absolute threshold
What does Weber’s Fraction depend on?
the sensory dimension measured as the value of standard stimulus is different between dimensions
How is perception measured above threshold?
Magnitude Estimation (Stevens, 1957)
What happens in Magnitude Estimation?
participants rate the size or intensity of a stimulus on a numerical scale in relation to a standard stimulus
True or False: Doubling Physical Intensity doubles the perceptual experience
False
Explain response compression:
the increase in perceived magnitude is smaller than increase in stimulus intensity
Explain response expansion:
the increase in perceived magnitude is larger than increase in stimulus intensity
What is Steven’s Power Law?
a power function used to describe the relationship between intensity of a stimulus and perception of its magnitude
What is the issue measuring perception when comparing two people?
The response of two different observer’s in constant stimulus where they have different thresholds. The response criteria between people may lead to erroneous conclusions about perceptual sensitivity
What are the four types of responses in the Signal Detection Experimenter?
hit or miss (when stimulus is actually present), false alarm or correct rejection (when the stimulus is absent)
Describe the perceptual approach:
perceptual representations of the world- measures detection and discrimination performance of visual stimulus
Describe the evolutionary/ecological perspective (active vision):
guidance of actions, primary role of the visual system is to guide our actions. vision is needed to explore and manipulate the world around us
What does the Perception-Action model refer to (AD Milner and MA Goodale, 1995)?
how perception and action relate in the human brain
What are the origins of the perception-action model?
origins in animal and neuropsychological research based on cortical processing mechanisms
what is the main idea of the perception-action model?
the idea that people’s perception of the world does not always follow the same rules as their behavioural interactions with this world
‘two visual stream model’ and ‘two visual systems hypothesis’ are other names for which model?
The Perception Action Model
What are the two streams involved in perception that are initiated after visual input?
the dorsal stream, and the ventral stream
what are the effects of lesion to the ventral stream?
lesion impairs recognition and identification of objects
what are the effects of lesions to the dorsal stream?
lesions impair perception of spatial relations between objects
Out of dorsal and ventral, which stream is conscious and which is unconscious?
Dorsal stream= unconscious
Ventral stream= conscious
What damage did Patient DF suffer, and how did this effect her? (agnosia)
Patient DF suffered bilateral lesions in area LOC of the Ventral stream. As a consequence she faced a visual form of agnosia where she struggled to recognise and identify objects
Despite visual agnosia, what abilities did Patient DF maintain in object perception?
she could still identify texture and colour of objects. her performance was normal in corresponding tasks for example when grasping to is able to adjust hand opening to object size
What region of the brain are the ventral and dorsal stream originated in?
the Primary Visual Cortex
What does the case of Patient DF provide evidence for?
suggests evidence that the ventral stream is important for perception such as recognizing size and shape of objects
True or False: dorsal stream damage is more common that ventral stream damage
true, ventral stream damage is very rare
What complications are associated with dorsal stream damage?
optic ataxia where patients struggle to perform visually guided actions but have no problem with perceptual tasks
What do studies of lesions to the dorsal stream provide evidence for?
evidence to suggest that the dorsal stream is important for visual guidance of actions
Describe double dissociation:
complementary effects of ventral and dorsal stream damages suggests the ventral stream mediates Vision for Perception, and the dorsal stream mediates ‘Vision for Action’
What are three limits of clinical case studies:
1) neuropsychological evidence on its own cannot prove the perceptual system is not involved in guidance of actions
2)patients may rely on different info or develop alternative strategies through brain plasticity
3)evidence is needed for the requirement of perception and vision for action in healthy brains
What do visual illusions initiate?
introduce a dissociation between conscious perception of size and real metrics of objects which are assumed to guide actions
Why are illusion studies not sufficient evidence of Perception-Action Systems?
results are controversial because distances between perception and action tasks can be explained without the assumption of distinct processing mechanisms
What part of the Perception-Action model is undisputable?
it is undisputed that ventral streams are relatively more important for perceptual processes and dorsal streams are more important for planning and guidance of actions. the degree of communications between the streams is controversial
What is the nature of modularity in the ventral stream?
neurons responding to similar stimuli are grouped together in brain areas
What is an example of the modularity in the ventral system in the brain?
Patient DF suffered deficits in perceiving form and shape however not all the ventral stream is damaged. Some patients with ventral stream damage that processes colour suffer from cerebral achromatopsia but have no problem processing shape
What is the difference in born or developed colour-blindness and colour blindness symptoms caused by cerebral achromatopsia?
colour blindness concerns actual colour receptors in the eyes whereas cerebral achromatopsia is caused by lesions to the ventral stream (brain damage)
What were the results of the study concerning response of neurons in a monkey’s inferotemporal cortex?
97% of the neurons in the face were face selective. cells responded to different views of monkey and human faces but had a much weaker response for other body parts
What is evidence for specialised face and object (double dissociation) in the ventral stream?
Prosopagnosia (unable to recognise faces but no agnosia for objects), and Object Agnosia (lose ability to recognise objects but no problem in recognising faces)
Describe the modularity in the dorsal stream:
based on nature of the actions that are guided by visual objects. most neurons in the dorsal stream do not fire unless some action is required towards a seen objects and there is modularity of certain movements
What was discovered regarding API neurons in the dorsal stream of monkeys (Murata et al., 2000)
the neurons are selective to shapes and specific grasp postures
What are the three main types of receptors in tactile perception and what do they respond to?
Mechanoreceptors: respond to mechanical stimuli i.e. pressure, stretching, vibration
Thermoreceptors: respond to temperature
Chemoreceptors: Respond to certain chemicals e.g. histamines
Why are Nociceptors undecidedly their own separate group of receptors?
they mediate perception of pain however they are potentially subtypes of chemoreceptors and mechanoreceptors
How are responses elicited from tactile receptors?
different types are distributed through the skin and respond to different touch stimuli and events
What type of receptor do the following subtypes belong to? : Merkel receptors, Meissner’s corpuscle, Pacinian corpuscle, Ruffini cylinder
Mechanoreceptors
For the following receptors; Merkel Receptor, Meissner’s Corpuscle, Pacinian Corpuscle, Ruffini Cylinder; describe the alternative labels (if any) size, borders, adaptation, stimulus, and distance to skin surface:
Merker Receptor: AKA Tactile disc. small receptors with sharp borders; slow adaptation; pressure, fine texture, and shape; close to skin surface
Meissner’s Corpuscle: AKA Tactile Corpuscle. small receptors with sharp borders; rapid adaptation; indentation, motion across skin; close to skin surface
Pacinian Corpuscle: AKA Lamellated Corpuscle. large receptors with diffuse borders; rapid adaptation; vibration and fine texture; deeper in skin
Ruffini Cylinder: AKA Ruffini Corpuscle. Large receptors with diffuse borders; slow adaptation; stretching; deeper in skin.
What are two ways to measure Tactile Acuity?
Two Point Threshold and Grating Acuity
Describe Two Point Threshold in Tactile Acuity:
classical measure in early touch research however vulnerable to confounds. The minimum separation between two points on the skin that are recognised as two point. This is the smallest discriminable difference between two points.
Describe Grating Acuity in Tactile Acuity:
Acuity for which orientation can still be accurately judged or at least 75% correct. Testing for horizontal vs vertical orientation. This is a more objective measure with no temporal effect.
What are the nature of the thresholds in Two-Point Threshold Method and Grating Acuity?
Grating Acuity Thresholds tend to be a bit lower in grating Acuity than the two-point method; 1mm vs 2-4mm
What do skin receptor properties determine?
Perceptual Experience when skin is stimulated
What is the Merkel receptor Mechanism?
respond to grooved stimulus patterns. the firing of the fibre reflects the pattern of grooved stimulus. this signals detail and texture
What is the nature of receptor density in sensitive body parts?
sensitive body parts have higher receptor density
What is better tactile acuity associated with?
higher density of Merkel receptors (most of the time)
What is an exception to ‘higher acuity for areas with higher density of receptors’, and what is this an example of?
The index finger pad has higher acuity than the pad of the little finger even though their receptor density is identical. These are cortical mechanisms
Aside from receptor density, what else contributes towards tactile acuity?
the size of the receptive fields of cortical neurons. Cortical neurons representing body parts with higher acuity have smaller receptive fields
What are the benefits of braille reading for tactile acuity?
intense braille reading can produce superior spatial acuity in both blind and sighted humans via changes in cortical representation
How does tactile acuity correlate with age?
Tactile acuity declines with age at a rate of about 1% a year
According to duplex theory of texture perception (David Katz), what cues does the perception of texture depend on?
Spatial cues: cues available to vision and touch. this is determined by size, shape, and distribution of surface elements (e.g. Braille letters)
Temporal cues: specific to touch. determined by the rate of vibration as skin moves across finely textured surfaces e.g. sandpaper.
What does perception of very fine textures require?
movements
Explain the study providing evidence for the duplex theory of texture perception:
Hollins and Risner (2000). Participants struggled to identify differences between two fine textures in static conditions but improved considerable when they were able to move their fingers over textures. Coarse surfaces were equally discriminable in moving and stationary conditions.
What is sensing fibre texture through temporal cues mediated by?
Perception of vibration
What did the adaptation paradigm involve?
temporarily inactivating different receptor types
Describe the procedure and the findings of the adaptation paradigm:
The Meissner Corpuscle, which responds to low frequencies, was adapted at 10 Hz for 6 minutes.
The Pacinian Corpuscle, which responds to high frequencies, was adapted at 250 Hz for 6 minutes.
The receptors were therefore deactivated.
After the adaption to 250Hz, vibration participants were unable to discriminate the two textures. This proves that fine texture discrimination depends on Pacinian Corpuscles
Why does touch provide a more reliable perception of surface texture than vision?
visually perceived surface texture is influenced by illumination. surfaces appear rougher with decreasing illumination angle. touch involves direct contact with a surface providing a more reliable assessment
How can touch become more accurate with very fine textures?
higher resolution and access to temporal cues
Describe the two afferent subsystems that mediate haptic perception:
Cutaneous/Tactile Input: Mechanoreceptors and thermoreceptors of the skin which mediate tactual experience
Kinaesthetic input: Mechanoreceptors embedded in the muscles, tendons, and joints which contribute to human perception of limb positions
What is usually involved in haptic perception?
active manual exploration
Why is haptic perception complex?
haptic perception requires close interplay between the sensory system (cutaneous sensations), the motor system (moving the fingers and hands), and the cognitive system (thinking about the information provided by sensory and motor systems)
Describe passive touch:
being touched. the ‘object’ is passively moved across the skin of the observer (no voluntary movement form the observer). this focuses perception on sensory/bodily responses such as skin sensation
Describe active touch:
touching objects. the observer moves actively with full control over their movements which engages haptic perception. Perception focuses on external object properties
In the somatosensory system theory, describe the ‘what’ and ‘where’ subsystem:
What= perception of material/surface properties. the systematic relationship between exploration actions and object properties. surface texture, compliance (deformability under force), thermal quality, weight, geometric properties (such as shape and size).
Where= where localisation can be referred to relative to
A) the sensory organ (where skin touch occurs depending on the spatial resolving capacity of the skin)
B) the environment (where space is a stimulus touched i.e. how do we localise points in space during haptic exploration when vision is unavailable)
Describe the ongoing debate regarding the somatosensory system:
there is a debate as to whether the somatosensory system can be divided into a what (perception of surface properties) and where (perceptual guidance of action, localisation of touch) subsystem
True of False: Haptic Space is anisotropic?
True, haptic space varies in magnitude depending on direction
What are the six most used exploration procedures assessing texxture, weight, hardness, volume, temperature, exact shape)? Lederman and Klatzky 1987
lateral motion (texture)
unsupported holding (weight)
pressure (hardness)
enclosure (global space and volume)
static contact (temperature)
contour following (global shape, exact shape)
How is the Pacinian corpuscles activated in manual exploration for Haptic Perception?
Optimal activation of neural responses enhance response of slow adapting Merkel receptors and create deep vibrations activating Pacinian Corpuscles
Describe the study that indicates use of two spatial reference frames:
Kappers and Koendering. task = adjust a test bar so it feels parallel to the standard bar.
Explain the two competing spatial reference frames?
Egocentric-when judging bar orientation this is related to the orientation of the hand touching the bar
Allocentric- orientation of the hand touching the bar differs depending on the location
Why is understanding affective responses to materials important?
understanding affective responses to materials can help to design human machine interfaces such as assistant robots or safe work tools
In Drewing and Colleagues (2017) study, what 6 perceptual dimensions and 3 affective dimensions were materials judged by?
6 Perceptual dimensions:
fluidity
roughness
deformability
fibrousness
heaviness
granularity
3 Affective Dimensions:
valence (pleasantness)
arousal (exciting/boring)
dominance
Why were fluid materials associated with higher arousal?
potentially due to less predictable skin stimulation
What materials were rated as least pleasant?
rougher materials
How does tactile acuity correlate with the density of Merkel receptors?
areas on the body with high acuity and high receptor density are also devoted a larger area of processing in the brain
why does the somatosensory homunculus have odd proportions?
areas on the body are represented disproportionally in the brain.
How is the S1 (Somatosensory cortex) organised? (Penfield and Rasmussen, 1950)
S1 is organised in maps corresponding to locations on the body
Describe the somatosensory homunculus:
Large areas for the hand and lips (which are most sensitive to touch). Small areas for legs and back (less sensitive). similar topographical representation in the motor cortex
What is meant by somatosensory cortex plasticity?
the map is not fixed. the homunculus varies based on individual experiences shaped by learning
What were the findings of classical experiments on owl monkeys regarding somatosensory plasticity? (Merzenich and colleagues 1987)
intensive stimulation of a skin area (3 months of training) causes an expansion of the cortical maps
What evidence from musicians supports neuroplasticity in humans? (Elbert et al. 1995)
violinists show enlarged somatosensory cortex of regions that receive touch from the tips of the left hand
Describe Focal Dystonia:
AKA Musician’s cramp. painless muscular incoordination. a neurological disorder characterised by loss of fine motor skilled movements during instrumental playing. the disorder is task specific to instrumental playing
What is a correlating factor with focal dystonia?
strong correlation between instrument group and localisation of the disorder. the hand with higher workload becomes affected and more often occurs in the dominant hand.
True or False: the primary source of focal dystonia is in the peripheral nervous system?
False- the primary source of the problem is in the brain. abnormal sensory functions cause issues in motor behaviour
What changes in the sensory cortex are observed in patients with focal dystonia?
patients with focal dystonia have abnormalities in hand/finger representation in the primary sensory cortex
what do animal studies suggest about the causes of focal dystonia?
repetitive input through training causes enlargement and then fusion of representations
what is the nature of perception in natural interactions with the environment?
it is multisensory
Info from the different senses can either be complementary or ———————
redundant/overlapping
how does multisensory information provide a more complete representation of the world?
multisensory info increases reliability of the percept and increases resistance to interference
What body system disentangles cases where stimulation of different senses may be related or unrelated?
Central Nervous System (CNS)
Define Multisensory:
more than one modality is used in perception
define Cross Modal:
interactions between different modalities. One sense affects perceptions provided by a different sense
Define Inverse Effectiveness:
degree to which a multisensory response exceeds the response of the most effective modality. Specific stimulus components decline as effectiveness of modality specific stimulus component increases
Define Peripersonal Space:
space immediately surrounding our bodies in which objects can be grasped and manipulated
Define extrapersonal space:
space beyond grasping distance
What are three simple heuristics for multisensory integration?
Temporal correlation
Spatial congruency
Inverse Effectiveness
Explain temporal correlation:
stimulation of different modalities occurs at roughly the same time
Explain spatial congruency:
stimuli in different senses come from approximately the same location
Explain inverse effectiveness:
reduced benefit of multisensory integration the stronger the unimodal signal of cross modal cue. multisensory response is stronger when one stimulus itself is weak.
Where do you find multi modal neurons?
in superior colliculus
What are multi modal neurons necessary for?
relevant for rapid orienting of attention
what are the nature of spikes produced by multisensory events compared to individual spikes?
spikes produced by combination of visual and auditory event is larger than individual neural spikes in response to visual and auditory stimuli. multisensory response is greater than the sum of uni-sensory responses
Describe super additivity in multisensory perception:
When both cues are weak the multisensory response exceeds the sum of the separate inputs
Describe additivity in multisensory perception:
as cues become stronger unisensory responses become stronger, the integrated response is not different from the sum of the responses to each component
Describe subadditivity in multisensory perception:
combined input is smaller than the sum of the two unisensory inputs, but still exceeds the largest single input response
Explain the neural mechanisms of the subcortical areas in sensory perception:
the superior colliculus has the highest proportion of multisensory neurons. the neurons show overlapping spatial maps for visual, auditory and somatosensory models
where is the superior colliculus and what is it important for?
located in the mid brain, important for orienting behaviour and fast motor reactions
Explain the neural mechanisms for Cortical areas in sensory perception:
Multisensory neurons are found in most areas, often in combination with unimodal neurons, even in areas previously considered modality specific.
what can neurons in the primary auditory cortex be activated by?
visual lip movements
what can neurons in the visual cortex be activated by?
they can respond to tactile cues
why are different sensory models combined?
for the best estimate of external properties
Describe the modality appropriateness hypothesis:
the modality that provides more reliable information is given more weight
What is an example of a phenomenon where vision strongly influences auditory localisation?
the Ventriloquist effect
what is the neural mechanism behind the ventriloquist effect?
vision is spatially more accurate and so is regarded as the more dominant model
define semantic congruency:
consistent meaning of two stimuli
What effect does semantic congruency have on multisensory stimulus?
semantic congruency strengthens multisensory stimulus integration and the corresponding behavioural performance
how does semantic congruency in visual and auditory stimulus affect the speed of participant responses?
there is faster target detection when visual stimulus is accompanied by a semantically congruent sound
What can incongruent information result in?
unexpected precepts due to sensory interactions such as audio visual illusion
What is the explanation behind the Parchment Skin illusion?
sounds modify tactile sensations. enhanced high frequency feedback makes the skin feel drier. the deprivation of one modality can modify development and integration of the remaining modalities
Why are blind people less susceptible to the Parchment Skin Illusion?
They have developed the ability to ignore irrelevant auditory input in tactile tasks. following visual deprivation extensive cross modal changes occur.
Describe the Modality Appropriateness Account in multisensory perception:
interference by a task irrelevant modality is reduced when processing accuracy of the task relevant modality. perception is dominated by a modality that provides the most reliable information
What was the outcome of the Parchment Skin illusion in sighted people and blind people?
robust illusion in sighted humans. only three blind participants showed small effects in the expected direction of the task.
Explain the consequences a blind woman suffered following bilateral occipital lesions following a stroke: (Hamilton et al., 2000)
the woman lost the ability to read braille as the occipital lobe is involved in decoding spatial and tactile information for braille reading
What was implied by the findings after a blind woman suffered bilateral occipital lesions?
this suggested there may be a critical period of susceptibility for recruitment of the occipital cortex for haptic information processing in the congenitally blind
Following a TMS study, what was concluded about the role of the visual cortex in early blind individuals?
occipital stimulation disrupted braille reading in blind participants but not tactile discrimination in sighted participants. the visual cortex is recruited for somatosensory processing for early blind people.
Why is the distinction between own body and the environment important?
it is crucial for human conscious experience
What is body ownership?
includes feeling the skin stretching around joints, feeling coolness and warmth, and feeling tension from muscles and tensions. body ownership is multisensory in nature
Four Perceptual Rules of Body Ownership in the Rubber Hand Illusion and Full Body Ownership Illusion:
Temporal synchrony
Spatial Rules
Tactile congruency rule
Humanoid Shape Rule
What happens to Rubber Hand Illusion strength at distances?
it decreases at far distances (30cm peri personal space)
Which areas of the brain respond with greater activation for combined visuotactile stimulation more than unimodal stimulation?
areas in the ventral premotor cortex and intraparietal sulcus
Which parts of the brain is body ownership associated with?
activation in the multisensory areas in frontal and parietal lobes. recent studies show consistent activation in area EBA of the ventral stream
In neuroimaging, what manipulation of temporal and spatial perception produced the largest activation?
largest activation when stimulus was spatially and temporally congruent
True or False: activation in intraparietal cortex is superadditive, response in pre motor cortex is superadditive:
False. activation in the intraprietal cortex is additive, and response in pre motor cortex is superadditive
How does the ventral premotor cortex correlate with illusion?
Activation in ventral premotor cortex correlates with the strength of the illusion
How much of the population are immune to induction of the Rubber Hand illusion?
about 30%
Why may there be individual differences in the Rubber Hand illusion?
immunity should relate to how visual, tactile, and proprioceptive information is weighted by the brain. people who rely on proprioceptive information such as gymnasts and dancers may be more resistant to the illusion
What is Proprioception?
the body’s ability to sense it’s own position and movements without relying on visual inputs
Describe the projection of ownership to advanced hand prosthetics:
synchronised brushing of participants stump and the fingers of a prosthetic hand produced Rubber Hand Illusion in 30% of amputees
How can people maintain ownership of a virtual hand in VR?
as long as it’s movements are temporarily and spatially congruent with movements of the real hand
Who said ‘My Experience is What I Agree to Attend To’:
William James, 1890
What is the Cocktail Part Problem an example of?
Dichotic listening
How does Dichotic Listening work?
Participants might listen to two messages simultaneously through headphones. when messages are played in on ear each it is easy to shadow one audio. Audio may sound like babbling unless the content is distinct
In Dichotic Listening, what are people unable to report about the unattended ear?
changes in language, the recording being played backwards, or any content
In Dichotic Listening, what are people able to notice in the unattended ear?
they can notice if the message suddenly becomes the same in both ears, and if there is a big change in pitch such as voices changing gender
List four Key Features of Attention:
limited capacity
selection
modulation
vigilance
What are three varieties of attention?
Endogenous vs Exogenous
Covert vs Overt
Other divisions
Describe endogenous attention:
controlled or modulate by internal goals. this is top down and voluntary
Describe Exogenous attention:
controlled or modulated by external events. this is bottom up, involuntary and reflexive
What is more important: Endogenous attention or Exogenous attention?
a balance of both is important
Describe Overt attention:
observable by others, accompanied by hand or eye movements
Describe Covert attention:
not directly observable by others, out of the corner of your eye
Are eye movements related to attention?
There is a close relationship between eye movements and attention
Drivers looking but failure to see errors, mobile phone use during driving or walking, and competitive sport examples of distraction and misdirection, are all examples of what?
Failures to Attend
Name three models of attention:
attention as filter, attention as spotlight, attention as glue
Describe Broadbent’s Selective Filter Theory:
basic physical properties are received by the brain, but a selective filter is needed for information processing
What is Selective Filter Theory largely based on?
Auditory attention and Dichotic Listening Task
What is the essential claim of Selective Filter Theory?
attention is necessary for identification
Describe the process of Selective Filter Theory beginning with ‘input’:
input——sensory(e.g. left or right)——filter—–perceptual or meaning analysis——–short term memory——response
Is attention necessary for identification according to Selective Filter Theory Critics?
Mackay 1973, found evidence some unattended info can be identified and/or influence subsequent processing
What evidence is there for unattended info being processed?
In the river scenario, bias shift (people were asked if they heard threw stones at ‘river or Lloyd’s’ found that people are shifted 5-9% towards picking the interpretation that fits the unattended ear’s content
What does Filter theory (Broadbent) suggest about attention and identification?
attention is necessary for identification
Why does some recent research suggest Broadbent’s filter theory is correct? (Lachter, Forster, Ruthruf 2004)
filter theory is essentially right, all evidence that unattended information is remembered has come from experiments that did not ensure this information was truly unattended
How many milliseconds does it take to switch between attention channels ?
100
what happens when attention is not controlled?
attention can shift and influence you
describe lexical decision tasks?
you must identify whether a string of letters is a real word or not. should always attend and report only the letter strings in the bottom row
under what conditions are responses be faster in the lexical decision tasks?
after repetition priming
according to filter theory, where is the ‘filter’ in the brain?
in the Inferotemporal Cortex; place of object recognition
what is the nature of Receptive Fields as you move through visual areas to the temporal cortex?
they become increasingly complex and increasingly large
what is the process of stimuli travelling to the inferotemporal cortex?
retina -> LGN -> visual cortex-> inferotemporal cortex
describe the Biased Competition Model: (Desimone and Duncan,1995)
attention is an emergent property of many neural mechanisms working together to resolve competition for control of behaviour
what does Biased Competition Model claim about Filter Theory?
there is no filter, stimuli compete to drive cells at multiple levels/area.
According to Biased Competition Model, what happens to non selected stimuli?
only a select number of things can be represented at a time, non selected stimuli are not represented
What is competition be biased towards in the Biased Competition Model?
competition can be biased to favour behaviourally relevant perceptual features
Describe Posner’s Spotlight Model (Michael Posner)
when the target appears where you expect it to, you detect it faster. this is consistent with idea of attention as internal eye/spotlight
true or false: endogenous and exogenous cues combined give the most powerful effect on detection reaction time
true
name some types of cues:
arrows, numbers, peripheral signals, auditory signals, faces looking left or right etc.
are faster Reponses at cued or uncued location?
faster responses at cued location, smaller at the uncued
describe cue validity:
cue validity can modify the probability that the target will be in the same place as the cue…
75% cue predicts the target location= strong cueing effects
50% ,un informative cue, purely reflexive cueing effects
25% counter cueing = reversed cueing effects
what is Stimulus Onset Asynchrony?
cue-target interval. allows you to measure the time course of the effect of the cue i.e do cueing effects get smaller or larger over time
name some spatial cues:
enhance contrast
distort object size
saturate colour
accelerate motion
increase duration
what effect do spatial cues have?
spatial cues enhance neural responses. enhancements matched the time course of reaction
what is the ‘priority map’ in the parietal lobe?
peaks of higher activity for priorities locations
what is a criticism of the Spotlight Model?
its more of a metaphor than a modal. there are many features and types of attention where the spotlight metaphor is not easily applied
Describe the two stage model of Feature Integration Theory:
Step One: specialised and separate visual brain areas process basic stimulus features
Step Two: attention directed to regions of visual field ‘glue’ features together into identifiable objects that now have continuity over space and time
How are features represented in the brain?
by different specialized networks
According to feature integration theory, how are features formed into a single object?
attention to spatial location binds all features in that location to a single object
Name three pieces of evidence for Feature Integration Theory:
- illusory conjunctions
-object segregation
-serial vs pop out search
what leads to illusory conjunctions?
failure to correctly bind features
what task can be done to initiate illusory conjunctions in participants?
divert their attention away from shapes by asking participants to report the digits
Which stage of feature integration theory defines an object?
The Feature Extraction stage
when will an object ‘pop’ out of the background, and what makes this harder, according to feature integration theory?
if the object can be defined based on a feature. objects defined by a combination of multiple features requires serial effort and attention to find
Describe serial search in Feature integration theory:
attention needs to serially inspect each item to determine if it is the target. target is a conjunction of two basic features; colour and orientation
on a search slope, what is added when reaction time increases (FIT)?
increase with each additional distractor added to the display
Describe pop-out search in feature integration theory:
target can be defined based on a single, unique feature. These can be detected without need for attention and search time is close to zero
What are pre attentive features (FIT)?
features that guide attention and so don’t need to be detected
What might constrain the attention and conjunction of features?
constrained by prior knowledge i.e. no blue bananas or fuzzy bicycles
What happens to features without attention?
collections of features are interchangeable resulting in inattentional and change blindness
Name at leas tone thing that is ‘definitely’ ‘probably’ and ‘maybe’ a feature? (FIT)
definitely: colour, motion, orientation, size
probably: depth, luminance, closure, curvature
maybe: lighting, glossiness, number, aspect ratio
What are some examples of things that are probably not and definitely not a feature?
probably not: novelty, letter identity
definitely not: conjunctions, category, identity, 3D shape
What version of the ‘Guided Search’ model are we currently on?
6.0
what does ‘Guided Search’ propose?
targets have guiding features that can be used to limit the search set rapidly. once limited to a subset, attention is guided to each candidate until target is found.
what aspects of visual search does the Guided Search model include?
visual acuity, decision making, memory
Is Guided Search a model of search or attention?
search, but has largely subsumed Feature Integration Theory
where in the brain is the ‘master map’ of attention?
the parietal lobe
how do patients with unilateral parietal damage present?
they have elevated illusory conjunctions and are slower in conjunction search in the visual field contralateral to the lesion
what happened to patient RM, with bilateral parietal damage?
‘Balint’s syndrome’, mis binds features even when presented centrally for 10 second durations (problems tying information together
What are challenged to Filter Integration Theory?
-even feature detection requires some attention
-visual search is complicated by eye movements, texture perception, crowding
-some feature integration seems to be done without attention
what different aspects of attention process do each theory highlights?
filter= limited capacity nature of attention where constriction is what it operates on
spotlight= how attention selects, shifts, and is maintained in different locations
glue=what attention does
What are the two attention systems?
Top down endogenous (dorsal), bottom up exogenous (ventral)
what does the dorsal attention system (top down, endogenous) attend to?
attending objects and locations that are relevant to our current goals, ignoring distractions
what does the ventral attention system (exogenous, bottom up) attend to?
the circuit breaker for the top down system. allows us to notice important but unexpected events
what definitely breaks the ‘circuit’ of attention control?
sudden onset and luminance changes, looming stimuli, other humans
what factors *might break the circuit of attention control?
unique features, dangerous objects, rewarding or valuable stimuli, emotion inducing stimuli
describe ‘attentional control settings’:
You configure your attention to detect a specific property.
Attention is captured by stimuli that share that property.
People can use either a “feature
search” filter (i.e. look for green) or “singleton detection” filter (i.e. look for the unique thing)
what happens to babies’ attention within an hour of birth?
they orient to objects with face like configurations over control objects
what happens in butterfly detecting task when a face stimulus is also present?
it takes longer to find the butterfly because attention is drawn to the face
what is required for novel combinations of features?
binding
does attention prioritise neutral or emotional stimuli?
emotional
what type of stimulus are anxious individuals bias towards and is this the same in non anxious individuals?
threatening stimuli.
there is no evidence of threat bias in non anxious individuals
what are two possible explanations for threat bias in anxious people?
1)threat processing is automatic in anxious individuals
2)attentional resources are always diverted to the task of identifying threatening stimuli
attention is directed to locations expected to —————–(fill the blank)
yield the most reward
What is the priority map in the parietal lobes highly sensitive to?
reward
what is ‘rewarding’?
goal achievement, pleasure, reducing uncertainty, sampling info relevant to the current task, obtaining novel and unexpected information
how could attention ‘routines’ relate to bottom up biases?
Experience with objects and events lead to efficient attention “routines” that look could like bottom-up biases
how do the two attention systems communicate?
Lots of feedback loops and crosstalk between systems. Attention leads to new information and that information then guides attention
what is a problem with distinguishing the two attention systems?
intuitively appealing division but not easy to define what is truly “endogenous” vs. “exogenous”
what are serial dependencies?
phenomena in which actions, perception, decisions, and memory of features or objects
are systematically biased toward visual experiences from the recent past
List features and objects which can be manipulated by serial dependencies:
orientation, position, colour, shape, numerosity, ensemble properties, aesthetics, complex motion, face identity/attractiveness, facial emotion, body size, face age
explain the perceptual illusion of the never-aging face:
it’s identity is continuously biased towards the past, as a result face looks younger
What happens as a result of continuously biasing our percept towards the past?
online serial dependence induces misperception and actively generates continuous change blindness
What are four manifestation of positive dependencies?
-action: biased motor and eye movements, changed reaction time
-perception: change in appearance
-decision: biased expectation/decision/confidence
-memory: biased memory
what tricks us into recognising actors and stunt doubles as the same person?
serial dependence in face identity. by merging identities over time different actors look identical when they are not
How can serial dependence play a role in radiology screening?
in tumour classification: if a present tumour appears like a previous benign tumour we are more likely to think it is benign
True or False: serial dependence in attractiveness is real
true
what is the neural mechanism debate for Serial Dependence?
whether serial dependence occurs in low level visual areas or high level ones
What is the proposed neural mechanism for serial dependence?
There may be different loci and neural mechanisms for different kinds of serial dependence on different levels of manifestations
is visual input stable?
Visual input is unstable because of body /eye movements, noise, occlusions etc.
How is the world we live in autocorrelated?
features and objects are relatively unlikely to change location or identity over time spontaneously
How is serial dependence a visual stability mechanism?
they facilitate perceptual stability of information such as features and objects over time, without re analysing the entire visual scene on every single ‘snapshot’
what are negative aftereffects?
phenomena in which actions, perception, decisions, and memory of features or objects
are systematically biased away from visual experiences from the recent past
Describe tilt after-effect:
Following adaptation to an oriented stimulus,
an oriented test stimulus appears to be tilted in the opposite direction
Describe motion after-effect:
Following adaptation to movement in a given direction, a stationary test pattern appears to move in the opposite direction
Describe colour after-effect:
Following adaptation to a specific colour,
a test stimulus appears to have the colour complementary to the adaption
Explain neural fatigue theory:
In the retina, the 3 types of color receptors
(cones) are most sensitive to either red, blue or green. When you stare at a particular color for too long, these receptors get “tired” or “fatigued.”.
After looking at the flag with the strange
colors, your receptors that are tired do not
work as well. Therefore, the information from
all of the different color receptors is not in
balance. Therefore, you see different color
“afterimages”
why has visual aftereffect been called ‘psychologist’s microelectrode’?
If physiologists found single cell tuned for a certain feature (face identity, motion, color, etc etc)
…then psychophysicists would find a corresponding negative aftereffect in face identity, motion color etc.
What is contradicting evidence of neural fatigue for the colour after-effect?
Although at its core it is a negative aftereffect,
it was shown to last for minutes, hours or even days
Neural fatigue cannot account for this negative aftereffect
Negative aftereffect was proposed to be a mechanism which maximises ———————–
constancy
what two main kinds of serial effects characterise visual perception across time?
-serial dependence
-negative aftereffect
