Chapter 2 - Perception Part 1 (Start - Perception & Action) Flashcards
What is the difference between perception and sensation?
Sensation refers to a PASSIVE process of bringing information from the outside world into the body and to the brain.
Perception is an ACTIVE process. Refers to the ACTIVE organization and interpretation of sensory information into something meaningful.
What are the 2 different types of theories we use to recognise patterns?
Templates and Features.
According to the template theory, what is a template?
Forms or patterns stored in long-term memory corresponding to each of the visual patterns we know.
Pattern is recognized when its template is matched to the stimulus input. -> provides closest match
List some pros and cons of using the template theory to recognise patterns.
Pros:
- Common-sense; a rather intuitive method
Cons:
- Matching will fail even with minor differences between the template and the input.
- Ill-equipped to account for the flexibility shown by people when recognizing alphabetical and numerical symbols –> becomes obvious when the stimulus belongs to an ill-defined category where no single template will suffice (eg building)
What are some assumptions you can make to improve template theories?
1) Assume that the visual stimulus undergoes a normalization process.
2) Assume that there is more than one template for each letter and digit.
How does the assumption that visual stimulus undergoes normalization help in pattern recognition?
Helps you to produce an internal representation of the visual stimulus in a standard position.
Makes you search for a matching template.
However, by assuming that visual stimulus undergoes normalization, are there any things you might be discounting?
You overlook the possibility that your visual stimulus might not always be consistent with your template.
Not possible for whatever stimulus you experience to always be consistent with your template.
With this (cannot assume normalization) being said, what other assumption should you make to make template theories more effective?
Should assume that there is more than one template for each letter and digit.
What are the advantages of assuming that there is more than one template for each letter and digit?
Permits accurate matching of stimulus and templates across a wider range of stimuli
Does considering the fact that each digit and letter has more than one template makes the template theory more complicated?
Yes.
What assumption is held by most feature theorists?
Pattern recognition first involves specific processing and is then followed by more global or general processing to integrate information from the features.
How did Navon prove that global processing CAN precede more specific processing?
Presented observers with stimuli (a big S formed with small S or small H or big H formed with small H and small S) - 4 conditions.
Found that performance speed with the small letters was greatly slowed when the large letter differed from the small letters. In contrast, decision speed with the large letter was not influenced by the nature of the small latter. In this case, we often see the forest/global structure/big letter before the tree/specific structure/small letter.
What did Neisser do that helped to lend support to the feature theory?
2 lists of non-words with a common target letter Z. For the first list, Z is beside unrounded alphabets that consisted of straight lines like Z itself, whereas in the second list, Z is beside unrounded alphabets.
Compared time taken to detect letter Z. Performance was faster in the latter condition because the distractors shared fewer features with target letter Z.
What types of cells did Hubel and Wiesel study?
Cells in parts of the occipital cortex (at the back of the brain) associated with the early stages of visual processing.
What did Hubel and Wiesel observe?
Some cells responded in 2 different ways to a spot of light depending on which part of the cell was affected.
- An “on” response with an increased rate of firing when the light was on.
- An “off” response with the light causing a decreased rate of firing.
What did Hubel and Wiesel discover?
There are 2 types of neurons in the primary visual cortex: Simple cells and complex cells.
What are the traits possessed by simple cells?
- Have “on” and “off” regions with each region being rectangular in shape.
- These stimuli respond most to dark bars in a light field, light bars in a dark field, or straight edges between areas of light and dark.
- Any given simple cell only responds strongly to stimuli in a particular orientation
Responses of these cells could be useful and relevant to feature detection.
What are the traits possessed by complex cells?
- Responds to moving contours
- We have more of these than simple cells.
The responsiveness of end-stopped cells depends on __________ and ___________.
stimulus length, orientation.
Pattern recognition involves both top-down processes and bottom-up processes. True or false?
True.
Use the word superiority effect to explain how pattern recognition involves top-down processes.
WSE: The finding that a target letter is detected faster when presented in words than in non-words. Suggests that information about the word presented can facilitate identification of its letters.
Top-down: Information about the word presented can facilitate identification of the letters.
What is the pseudoword superiority effect?
Letters are easier to identify when presented in pseudowords than in nonwords.
What patterns do you observe in medical diagnosis when it comes to pattern recognition?
Experts are more likely than non-experts to use implicit reasoning, whereas the non-experts made more use of analytic reasoning. However, other evidence indicates that medical experts often start with fast, automatic processes but cross-check their diagnoses with analytic ones.
Explain interactive activation model and top-down activation.
Negative example: If it’s a non-word, there’s no top-down effect, and hence words won’t be activated first before letters are activated.
What are some challenges one would face in object recognition?
Think:
- Number
- Camera lens and Facebook 360 function.
- Do all objects look the same?
- What did Gestalt psychologists come up with about perceptual segregation?
1) Numerous objects in the visual environment, many of which overlap, and are overlapped by other objects.
2) We recognize an object over a wide range of viewing distances and orientations.
3) Objects vary greatly in their visual properties.
4) Figure-ground segregation: You have to figure out which part of the visual field is the figure (more important), and which part is the ground (less important).
What are the main law associated with figure-ground segregation, and what are some examples of this law?
Explain the main law and these examples.
recall PREGNANT.
Law of Pragnanz: The notion that the simplest possible organization of the visual environment is what is perceived.
1) Law of Proximity: VIsual elements tend to be grouped together if they are close to each other.
2) Law of Similarity: Elements will be grouped together perceptually if they are similar.
3) Law of Good Continuation: We group together those elements requiring the fewest changes or interruptions in straight or smoothly curving lines.
4) Law of Closure: Missing lines are filled in to complete the figure.
Why is the figure more important than the ground?
The figure is perceived as having distinct form or shape, whereas the ground lacks form.
Figure is perceived in front of the ground, and the contour separating the figure from the ground belongs to the figure.
Does figure-ground segregation require past experience (at least what the Gestalt psychologists suggested)?
Is there any evidence to show this?
No, depends very little on past experience and knowledge –> hence de-emphasized the role of past experience and knowledge.
When observers were presented with atypical shape contours that were hard to interpret, they showed rapid and flexible learning, which led to a rapid improvement in performance.
What did the Gestalt psychologists assume about figure-ground segregation?
Hint: If little past experience is needed do you think it’s more innate or learned?
Occurs very early in visual processing and always precedes object recognition.
What did Irving Biederman argue in his recognition-by-components theory? What did he also assume that was found to be incorrect?
Suggested that all objects consist of basic shapes called geons (geometric ions).
Approx 36 geons which can be arranged in limitless combinations.
Object recognition is viewpoint-invariant.
While it can be said that we are most sensitive to those visual features of an object directly relevant to identifying its geons, is there any evidence to show that this isn’t always the case?
1) Himba: a seminomadic tribe in NW Namibia.
- Debunks the notion that we develop sensitivity to visual features of an object as these people have very little exposure to manufactured objects.
- However, they are still as sensitive to geon-relevant information as individuals living in the developed world.
- What seems to matter is exposure to a great variety of naturally-occurring objects in the world around us.
2) Intact figures with degraded line drawings either preserving or not preserving parts of the contour providing information about the concavities.
- Concavities in an object’s contour provide especially useful information.
- Object recognition was much harder to achieve when parts of the contour providing information about concavities were omitted than when other parts of the contour were deleted.
Illustrate how object recognition involves both top-down processing and bottom-up processing.
BTU: Identify geons first, then you identify object –> strongly emphasised in object recognition
TD: Depends on factors such as expectation and knowledge are often important, especially when object recognition is difficult.
- Observers relied more on top-down processes if an animal picture is blurred as compared to when it is not blurred.
- Happened because there was less information for bottom-up processes to make use of with the blurred photographs.
Having established that object recognition can be both viewpoint-variant and viewpoint-invariant, when are viewpoint-invariant mechanisms used?
When object recognition involves making easy discriminations.
When will viewpoint-variant mechanisms be used?
When object recognition requires difficult within-category discriminations.
What did Tarr et al obtain with regard to the point about object recognition being both viewpoint-invariant and viewpoint-variant?
Considered recognition of the same 3D objects under various conditions.
Performance was close to viewpoint-invariant when the object recognition task was easy (and detailed feedback was provided after each trial). However, it was viewpoint-variant when the object recognition task was difficult (no feedback given after the task).
Which brain areas are activated during visual processing?
Visual processing proceeds through several areas in the occipital lobes at the back of the brain and finishes up in the inferotemporal cortex, which is of crucial importance in visual object recognition.
What do neurons vary in?
Invariance or tolerance.
What does it mean when a neuron possesses high tolerance, and what does it mean when a neuron possesses low tolerance?
High: Neurons responding almost equally strongly to a given object regardless of its orientation, size and so on.
Low: Neurons responding most strongly to an object in a specific orientation or size.
Is there any link between a neuron’s tolerance and the invariance of viewpoints adopted during object recognition?
Inferotemporal neurons having high invariance or tolerance seem consistent with theories claiming that object recognition is viewpoint-invariant.
(High tolerance -> invariant)
Inferotemporal neurons having low invariance or tolerance seem consistent with theories claiming that object recognition is viewpoint-variant.
(Low tolerance -> variant)
Can object recognition be both viewpoint-invariant and viewpoint-variant at the same time?
Yes.
Observers saw pairs of simple 3D objects formed from connected cylinders. Task was to decided whether the 2 images show the same object or different objects.
When 2 objects were different, they could differ in terms of a viewpoint-invariant feature and/or viewpoint-dependent features.
Key finding was that observers used both kinds of information. Suggests that we make use of all available information in object recognition rather than confining ourselves to only some of the information.
What is agnosia?
When one cannot recognise objects despite information reaching the visual cortex.
These people have no problems with their eyesight and visual cortex, but they cannot recognise objects.
What are the 2 kinds of agnosia?
Apperceptive agnosia: Object recognition is impaired due to deficits in perceptual processing.
(cannot perceive)
Associative agnosia: Perception is fine, but there is difficulty retrieving knowledge about objects from long-term memory. (cannot retrieve_
Apperceptive –> cannot perceive
Associative –> cannot retrieve.
The problems with object recognition occur at a(n) ________ of processing in apperceptive agnosia than in associative agnosia.
earlier or later?
Earlier
maybe just think of it as you need to perceive before you retrieve. perceiving would thus be an earlier stage.
How do we distinguish between apperceptive agnosia and associative agnosia?
1) Assess patients’ ability to copy objects they can’t recognise
- Can copy: Associative agnosia
- Cannot copy: Apperceptive agnosia
2) Gollin picture test: patients are presented with increasingly complete drawings of an object.
- Apperceptive agnosia patients would require more drawings than healthy individuals to identify the objects.
While many patients with apperceptive agnosia have problems at early stages of perceptual processing, are there any exceptions which show that the distinction between apperceptive and associative agnosia is oversimplified?
Eg of early stage:
Studying a patient (SA), a hospital clerical worker with apperceptive agnosia.
- Had great difficulties in shape discrimination and in copying complex workings.
HJA: A male patient with apperceptive agnosia
- Had problems at a later stage of processing.
- Performed well on tasks involving shape discrimination and copying drawings, but found it very hard to integrate visual information
- Able to cope with recognizing many common objects, if they are standing alone.
- However, if they are placed together, he finds recognition more difficult.
CH is a 63 y.o woman suffering from apperceptive agnosia. She had to decide whether a piece of fruit was present in photographs of everyday scenes, a task on which her performance was poor. Inspection of CH’s eye movements revealed that she failed to focus on areas most likely to contain a piece of fruit. What does this say about some patients with apperceptive agnosia?
They have severe problems with top-down processes based on knowledge. In this case, CH couldn’t use top-down knowledge of the structure of visual scenes to guide her eye movements.
What are the stages of object recognition?
1) Form and shape processing
- Many apperceptive agnosics experience problems here.
2) Integrating or combining information about an object’s features
- Some apperceptive agnosics start experiencing problems here.
3) Observers gaining access to semantic knowledge about objects after they’ve gained a detailed structural description of those objects.
- Some patients with associative agnosia face problems here.
How does face recognition differ from the recognition of other objects?
Faces, compared to objects, are processed more holistically. This is done because information about specific features of a face can be unreliable, and also because facial features can change.
What is the part-whole effect? Use an example (Farah, 1994) to explain it.
Part-whole effect: Memory for a face part is more accurate when presented with its whole face rather than on its own.
- Participants were presented with drawings of faces or houses, and associated a name with each face and each house.
- After that, they were presented with whole faces and houses or with only a single feature.
Recognition performance for face parts was much better when the whole face was presented rather than only a single feature. In contrast, recognition performance for house features was very similar in whole and single-feature conditions.
What is prosopagnosia?
Popularly known as “face blindness”
A condition mostly caused by brain damage in which there is a severe impairment in face recognition with little or no impairment in face recognition. Suggests that object and face recognition tap separate systems and brain areas.
What are the possible reasons that prosopagnosics have poor face recognition but reasonable object recognition?
1) They have suffered damage to a part of the brain specialized for processing faces.
2) Face recognition is simply harder than object recognition.
What are the possible reasons that prosopagnosics have poor face recognition but reasonable object recognition?
1) They have suffered damage to a part of the brain specialized for processing faces.
2) Face recognition is simply harder than object recognition. Face recognition involves distinguishing among members of the same category, whereas object recognition only involves identifying the relevant category.
What is the brain area associated with face processing?
Fusiform face area. Located in the inferotemporal cortex.
What did Bruce and Young propose in their face recognition theory?
When we look at a familiar face, we first access familiarity information followed by personal information (eg person’s job), followed by the person’s name.
Familiarity information -> personal information -> person’s name
What did this modified theory propose about the face recognition theory?
1) Observers decide whether the stimulus they are looking at is a face (face detection)
2) It is then matched to a memory representation (face memory)
- Structural encoding of the face can also be used for recognition of facial expression and gender discrimination.
Complete these sentences about some assumptions made in the face recognition theory.
a) _________ stage of processing involves deciding whether the stimulus at which we are looking at is a face or not.
b) _________ processing routes are involved in the processing of facial ______ and facial __________
c) We retrieve personal information about a person _____ we recall their name.
a) Initial
b) Separate, identity and expression.
c) before we recall their name
Is it possible for an individual with face blindness to be good at facial identity and poor at identifying facial expression, and vice versa?
Yes. Supports 2nd assumption.
Young et al (1985) asked people to keep a diary record of problems they experienced in facial recognition. There were 1008 incidents in total, but people never reported putting a name to a face while knowing nothing about the person. In contrast, there were about 190 instances where someone remembered a reasonable amount of information about a person but not their name.
What assumption does this piece of evidence support?
Supports the assumption that we retrieve personal information about a person before we recall their name.
However, are there any instances whereby the 3rd assumption can be debunked?
Yes. 3rd assumption found to be too rigid. Frequent exposure to names of close colleagues will allow you to name them faster than you can retrieve personal information about them.
However, despite this, do take note that it is typically harder to retrieve someone’s name than to retrieve personal information about them.
Genetic factors play no role in determining one’s recognition ability. True or false?
False.
Visual perception relies on _________ processes whereas visual imagery relies on __________ processes.
Bottom-up; top-down.
What is visual imagery?
Forming a mental representation of an object in the absence of the relevant stimulus in the environment.
Perception: rooted in real life.
Imagery: exists only in your mind.
so hallucination is visual imagery.
While people often do not confuse visual perception with visual imagery, there are still individuals with eye disease who suffer from a condition whereby they form vivid and detailed visual hallucinations that are mistaken for visual perception. What is this condition?
Charles-Bonnet Syndrome
What did Kosslyn propose and assume in his perceptual anticipation theory?
The mechanism used to generate images involve processes used to anticipate perceiving stimuli.
Hence, this statement assumes that there are close similarities between visual perception and visual imagery.
VIsual images are like ________________; they are like pictures or drawings in that the objects and parts of objects contained in them are arranged in space. Information within an image is organized spatially in the _____ way as information within a percept.
depictive representations.
same.
What is the “visual buffer”? Which areas are particularly important to it?
Refers to the brain areas in which the depictive representations are formed, among which Areas 17 and 18 are of special importance.
Where are depictive representations created at?
Early visual cortex in occipital area at the back of the brain. Consists of the primary visual cortex (BA17) and seconday visual cotex (BA18).
What are the differences in visual buffer processing between perception and imagery?
Perception: Visual buffer processing depend primarily on EXTERNAL STIMULATION.
Imagery: VIsual images in the visual buffer depend on non-pictorial, propositional information stored in long-term memory.
Visual long-term memories of shape are stored in ___________, whereas __________ representations are stored in the posterior parietal cortex.
inferior temporal lobe, spatial
What is the difference between Kosslyn’s perceptual anticipation theory and Pylyshyn’s propositional theory?
K: Mechanisms used to generate images are used to anticipate perceiving stimuli.
P: Performance on mental imagery tasks does not involve depictive or pictorial representations. Instead, what is involved in tacit knowledge (knowledge not generally accessible to conscious awareness)
If visual perception and visual imagery involve similar processes, they should influence each other.
_________ effects if the content of perception and image is the same
_________ effects if the content of perception and image is different
Facilitative
Interferecnce
What is binocular rivalry?
Binocular rivalry
When two different stimuli are presented one to each eye, only one is consciously perceived at any given moment.
If one stimuli is presented shortly beforehand, that increases the chances it will be perceived in the binocular rivalry situation.
Are there any findings to support the presence of facilitative effect?
Observers initially perceived a green vertical grating or a red horizontal grating. They were then later subject to the binocular rivalry condition. The facilitation effect was obtained and was greatest when the orientation of the grating in both conditions were the same.
Even when initial single grating was imagined rather than perceived, a similar facilitation pattern was observed. Suggests that visual imagery involves similar processes to visual perception.
Are there any findings to support the presence of interference effect?
Participants rated the vividness of visual or auditory images under control conditions (no additional task) or while performing another task involving visual/spatial processes (counting aloud repeatedly from 1 to 10).
The visual/spatial task reduced the vividness of visual imagery more than auditory imagery because some of the same mechanisms were involved on the visual/spatial task and visual imagery task.
What are the 3 factors that influence whether early visual cortex was activated during visual imagery?
1) The nature of the task: Imagery tasks requiring participants to inspect fine details of their visual images were much more likely to be associated with activity in the early visual cortex than were other imagery tasks.
2) Sensitivity of brain-imaging technique
- More sensitive technique (eg fMRI) –> more evidence that early visual cortex was involved in visual imagery if such tools are used as compared to
- Less sensitive technique (eg PET)
3) Shape-based vs scanning tasks:
- Early visual cortex more likely to be activated during visual imagery when the task required processing of an object’s shape than when you’re simply asked to imagine an object in motion
- Can imply that spatial processing and visual processing involve different brain areas.
Since activation in early visual cortex is associated with visual imagery, you can say that activation in early visual cortex is ESSENTIAL for visual imagery.
- True or false?
FALSE.
However, what can be done to produce a causal relationship between activation in early visual cortex and visual imagery?
Recall: Kosslyn and lines
Participants memorized a stimulus containing 4 sets of stripes, after which they formed a visual image of it and compared the stripes in terms of their relative width.
Immediately before performing the task, some participants received rTMS applied to area 17. rTMS significantly impaired performance on the imagery task, thus showing that it is causally involved in imagery.
Is there any evidence to show that the processes involved in visual imagery closely resemble those in visual perception?
Participants were presented with flickering black-and-white, bow-tie shaped stimuli with a horizontal or a vertical orientation in the perceptual condition. If you’re allocated to the imagery condition, all you have to imagine the bow tie in a horizontal orientation or a vertical orientation.
Found that for both conditions, there was more activation within early visual cortex in the vertical direction when the stimulus was in the vertical orientation. Same case for horizontal also.
If you compare the patterns of activation across most of the brain in visual perception and imagery, you would find that there is extensive overlap in the brain areas associated with perception and imagery. However, which 2 brain areas are particularly pertinent in this aspect?
Frontal and parietal areas since the cognitive processes involved in both imagery and perception are similar.
Which brain areas activated during imagery are also activated during perception?
Temporal and occipital regions.
Like let’s say event A is imagery, then event B is perception. A intersect B = temporal and occipital regions. –> visual imagery involves only some of the processes involved in visual perception.
Which brain areas activated during imagery are also activated during perception?
Temporal and occipital regions.
Like let’s say event A is imagery, then event B is perception. A intersect B = temporal and occipital regions. –> visual imagery involves only some of the processes involved in visual perception.
Estimated that visual imagery tasks are associated with activation in about 2/3 of the brain areas activated during visual perception.
Complete this sentence.
Perception necessarily involves more ___________ organization than imagery, and imagery relies more heavily on _____ and ________ processes.
low-level organisation
memory
top-down
What did Kosslyn find when he asked participants to memorize a map of an island with 7 locations?
Time taken to move in mental map corresponds almost perfectly to the physical distance on the map.
Good correspondence between spatial processes in the real world and in mental imagery.
When students were asked to imagine a cube balanced on one corner and then cut across the equator, what did the say the shape of the cube was, and what is its actual shape?
What does this suggest about imagery and perception?
Pyramid
Hexagon
Imagery does not resemble perception. Images often consist of simplified structural descriptions omitting important aspects of the object being imagined.
There are patient with impaired visual imagery but intact visual perception. Why does this occur?
With that being said, what do such people do when asked to draw objects?
They suffer damage to the left temporal lobe.
Happens because much of our knowledge of concepts, including objects, are stored there.
Can draw the objects when you show them a picture of it. So if you show them a picture of an iPhone they can copy it.
But if you tell them “draw an iPhone for me” without showing them a picture of it, chances are that they cannot draw anything out. Poor at drawing objects from memory. Recall that visual imagery relies quite a fair bit on what’s in your long-term memory.
Where are visual images generated from?
information stored in temporal lobes.
What is Anton’s syndrome?
A condition in which blind patients mistakenly believe that visual imagery is actually visual perception.
Intact visual imagery but impaired visual perception.
Which part of the brain is damaged in people with Anton’s syndrome?
Recall: Which part of the brain is essential for visual imagery?
Early visual cortex.
When carrying out research on mental rotation, what was a key assumption made?
Is there strong support for this assumption?
If we use mental rotation, the time taken to decide whether 2 objects are identical will be longer if more rotation is required.
Yes, regardless of whether rotation was required in 2 or 3 dimensions.
Why is mental rotation important?
- need good spatial processing to move successfully around the environment -> ability to perform mental rotation accurately and rapidly is an indication of such processing skills.
Males are actually not better off than females when it comes to spatial ability even though some experiments may show otherwise. True/false?
Can practice allow females to perform on the same level as males?
True. Only very modest effects found actually.
Yes.
In countries whereby there is a high level of gender equality, males and females perform equally well in tests of spatial ability. True or false?
FALSE.
Use the hunter-gatherer theory to explain why there is a gender difference in mental rotation.
Last time men went out to hunt. Need good spatial ability to find their way back home. Women would need a different set of spatial skills in order to gather plant resources.
Primary visual cortex in occipital region of the brain + temporal lobes (associated with the storage of object and concept information) -> they are involved in mental rotation.
True or false?
False.
Different types of processing needed.
The areas listed are required for visual imagery. As for mental rotation, since you need to use spatial and motor processing, the brain areas most associated with mental rotation should differ substantially from those areas used during visual imagery.
By using transcranial magnetic stimulation, what can be said about the regions essential for efficient mental rotation?
Use TMS to produce brief inhibition of processing in the parietal region.
Found that performance on mental rotation tasks was impaired. Can say that parietal regions are essential for mental rotation
(perhaps, you can only come close to making a causal relationship between a function and a brain area by doing a ‘negative’ experiment? like you show that something is impaired when you inhibit something, and not that something is activated when you do something).
Name another brain region involved during mental rotation.
Motor areas in the posterior frontal cortex.
Name 2 types of visual illusions.
Muller-Lyer illusion: recall arrow
Ponzo illusion: train track
How many visual systems do we have and what are their names?
Two.
Vision-for-perception system (VfP)
Vision-for-action system? (VfA)
What is the function of the VfP system?
Used to identify objects (eg is this a cow or a chicken?)
Used when we look at visual illusions.
What is the function of the VfA system?
Provides accurate information about our position wrt to an object. Used for visually guided action.
There is a _____ or _____ pathway going to the __________ cortex corresponding to the vision-for-perception system.
“what” or ventral
inferotemporal
Recall this way. Since you need this system to help you recognize objects, you’ll probably ask yourself “WHAT is this thing?”
There is a _______ or _______ pathway going to the ______ cortex corresponding to the vision-for-action system.
“where or how” or dorsal
Parietal
Recall this way. You need this system to find out your position wrt to an object. Will probably concern yourself with “HOW am i supposed to move from WHERE I am to there”
Explain how both systems work using the Muller Lyer illusion.
Present people with 3D version of this illusion.
Expect that illusion will be present if the participants were asked which line was longer.
- involves the vision-for-perception system
However, illusion should disappear if they pointed at the end of one of the 2 figures, because that would involve the vision-for-action system.
Mean illusion effect: 22.4% (P) vs 5.5% (A) -> effect was 4 times greater with the VfP system than with the VfA system
The 2 systems operate independently from each other. True or false?
False. They are not separated neatly and tidily, and there is considerable interchange of information between them
How does the hollow-face illusion work?
A realistic hollow mask looks like a normal face. A target (a small magnet) was placed on the face mask or on a normal face.
What are the 3 tasks that participants were assigned to?
1) Draw the target position (using the vision-for-perception system)
2) Make a fast flicking finger movement to the target (using the vision-for-action system)
3) Make a slow pointing movement to the target (involves both systems)
Which conditions in the face mask experiment resulted in a strong illusory effect.
1 and 3
Drawing the target position and making a slow pointing movement to the target.
Why would condition 3 result in a strong illusory effect even thought the VfA system was used?
If an action is preceded by conscious cognitive processes, it would involve the VFA and VFP systems.
Distinguish between effective and appropriate grasping.
Use the vision for perception system.
Eg: can grasp a toothbrush EFFECTIVELY by its handles, but to do so appropriately, you have to access stored knowledge about what a toothbrush is before you hold it by its handle.
Is there evidence to suggest that retrieval of knowledge using VfP is necessary for appropriate grasping.
Asking people to pick up various objects with handles.
Handle always pointed away from the participant, and the measure of interest was greatly impaired when they performed a learning task involving retrieving words from LTM at the same time.
