problem 4 - semantic memory Flashcards
what is a category?
A set of objects that can be treated as equivalent in some way
Most categories share more than just 1 property
- (eg. you know things about a Toyota car even if you only know other car brands, bc different cars have similar characteristics)
what is a concept?
Mental representation we form of categories
- Assume that ppl’s concepts correspond more or less closely to the actual category
- Allow us to be able to know what to do in new situations & when confronting new objects even if you’ve never experienced it before
- Allow you to extend what you have learned about a limited number of objects to a potentially infinite set of entities
nature of categories
Traditionally assumed that categories are well-defined = you can give a definition that specifies what is in & out of the category
- Provides the necessary features for category membership
- Those features must be jointly sufficient for membership
However, it has not been possible to find definitions for many familiar categories bcuz the world is messy & unclear
what are borderline category members?
not clearly in or clearly out of the category - deals with the fact that for categories there are no clear boundaries
what are fuzzy categories?
Have unclear boundaries that can shift over time
what is typicality (categories)
Even among items that clearly are in a category, some seem to be ‘better’ members than others
Ranging from the most typical (the prototype) to borderline members (not clearly in or out)
- items that are less & less similar to the prototype become less & less typical
sources of typicality (categories)
- The frequency with which we encounter the object
- Does have some effect, but is not the most imp variable - Family resemblance theory = items are likely to be typical if they:
- Have the features that are frequent in the category
- Do not have features frequent in other categories
what are category hierarchies?
More concrete categories are nested inside large, abstract categories
- Basic level of categorization
basic level of categorization
The neutral, preferred category for a given object, at an intermediate level of specificity
- Depends on people’s knowledge & interest in the category
Basic level categories are more differentiated: the category members are similar to one another, but they’re different from members of other categories
goldilocks effect (categories)
Category used for something not too small (eg. brown bear) and not too large (eg. animals) but just right (eg. bear)
what is psychological essentialism?
People tend to believe that some categories have an underlying property that is found only in that category & that causes its other features
what is essence (categories)
The intrinsic nature or indispensable quality of something, especially something abstract, which determines its character
Many categories don’t actually have essences
signs of essentialism
- Objects are believed to be either in or out of the category (no in-between)
- Resistance to change of category membership or of properties connected to the essence
- For living things, the essences is passed on to offspring
category verification task
Used to determine how we access categorical knowledge
- Asked to verify deny simple statements (e.g. a penguin is a bird or a robin is a bird) as quickly as possible
- Speed is the most imp variable in these tasks - fact that p’s verify that a robin is a bird more quickly than a penguin = tells us smth about how knowledge is organized
feature verification task
Used to assess how the features of categories are stored & accessed
- Asked to verify or deny sentences like ‘a cat has pointy ears’ or ‘a cat has skin’
- Fact that p’s verify that cats have pointy ears faster than having skin = tells us smth about the proximity of these features to the concept ‘cat’
what are semantic networks
Knowledge is stored in the form of associative networks in which concepts are represented by nearby nodes that correspond to related concepts or features of a given concept
- Related to but not based on brain structure
- Nodes in semantic network models: correspond to specific concepts & the link between them correspond to relationships among concepts
what is the spreading activation model
Makes a number of assumptions about the representation of knowledge + central assumption that concept nodes are linked in an associative network
Links that connect concepts represent a variety of relationships:
- Category membership (canary → bird)
- Property to concept relationships (yellow → canary)
- More subtle relationships (canary → cat)
what is the process of activation according to the spreading activation model?
A given concept is presented → corresponding node is activated → activation spreads out to other concepts in the network
- Strength of activation decreases w time, distance & the number of concepts activated (more concepts activated = the less activation)
- The activation that reaches any concept node is summed up & if the activation passes a threshold value, that concept will be activated
what is semantic priming?
Semantic priming = the tendency for the processing of 1 stimulus to enhance or speed up the processing of a related stimulus
- eg. yellow primes for sun, canary & lemon
- Yellow give head start towards the threshold
what are natural categories?
Those that occur naturally in the world - essentially define themselves
- Members share important features
- E.g. flowers, animals, trees
what are artifact categories?
Objects or conventions designed or invented by humans to serve particular functions
- Members don’t seem to share the same type of basic features
- E.g. tools, sports, furniture
what are ad hoc categories?
Formed in the service of some goal
- Members cohere only bcuz of their relation to the context at hand
- Share very little similarities or none at all
- E.g. things that ppl take on holiday
what are metaphorical concept?
- abstract concepts, don’t have a lot in common
- can be completely different in what they are but a common theme unites them - eg. dead-end job, abusive relationship, moral dilemma
what is similarity-based categorization?
Asserts that categorization is a matter of judging the similarity between the target object & some standard in LTM
- Either a clearly specified set of features: classical view
what is the classical view of concepts?
Items are classified into particular categories if they have certain features/characteristics - categories are traditionally assumed to be well-defined = either IN or OUT
- Features are both necessary & sufficient for defining the concept
- Categorization is based on whether the set of features that characterise a given item is similar to the features that define the concept = similarity based view
criticisms of the classical view of concepts
Many concepts are difficult to specify in terms of necessary & sufficient features - due to the rigidity of category boundaries
Doesn’t account for the typicality effect (graded structure of items) → cannot explain why chair comes up more often when we think of a furniture than a carpet (MOST IMPORTANT criticism)
Doesn’t take into account fuzziness / borderline members & ignores psychological essentialism
what is the prototype theory of concepts?
People have a summary representation of the category → a mental description that is meant to apply to the category as a whole
- Features are weighted by their frequency in the category
- When you try to classify an item - you see how well it matches that weighted list of features
Typical category members have more higher-weighted features = easier to match them to ur conceptual representation
- Less typical = fewer/lower weighted features = don’t match representation as well
criticisms of the prototype theory of concepts
The simple average of people’s representations of concepts does not capture the complexity & sophistication - we have sensitivity for how certain features within categories go and don’t go together
Prototype is not context-sensitive
Can’t explain conjunction (co-occurrence) of concepts
what is the exemplar theory of concepts?
Denies that there is a summary representation: instead, claims that ur concept of an item is remembered examples of that item you have seen
See an object –> compare it to the exemplars in your memory & judge how similar it is to exemplars in diff categories
- These similarity scores are added up for each category, compared & the category w the highest score is chosen
criticisms of the exemplar theory of concepts
In some circumstances people are truly using abstracted summary representations - one that’s constructed from repeated encounters
Surely not every single interaction with every single item is stored in memory, and if not - how is determined with ones are & which ones are not
Method: same items shown over and over again, lab is unlike the real world
current combined view of concepts
Concepts are represented through multiple cognitive systems:
- General descriptions (eg. dogs have 4 legs)
- Memories of exemplars: your grandmas dog
- Some categories involve rules (eg. all babies have a rooting reflex)
- General knowledge (eg. dogs have a brain)
what is semantic memory?
knowledge about objects, facts & concepts + words & their meanings
what is semantic dementia?
Associated with temporal lobe atrophy → impairment of conceptual knowledge
- Progressive deterioration of conceptual knowledge that supports semantic performance, independent of modality
- Research on patients with this condition suggests that conceptual knowledge is supported by a central system
Bozeat et al (semantic dementia article) - method
8 control p’s + 6 p’s w temporal lobe atrophy
- P’s asked to draw items from a list
- Drawings from patients compared to controls for amount of features they contained
- Patients had to take other tests to assess cognition & skills
- After tests, patients had to make drawings of 64 objects with unlimited time
Bozeat et al (semantic dementia article) - results
- Patients drew a lot less target features than the controls = damaged conceptual knowledge
- Sig correlations in perf between drawing assessment, object naming & word-picture matching → all these tasks require conceptual knowledge: there’s selective damage to central conceptual knowledge
- Familiarity of an item led to better success in drawing
Bozeat et al (semantic dementia article) - conclusion
- P’s w semantic dementia produced sig less info & features than the control group
= there is damage to central conceptual knowledge - When a patient knew an object well, they usually knew how to draw more features of this object.
- The features that frequently appeared in a category were often drawn
