Cognitive Psychology by K. Gilhooly, F. Lyddy, and F. Pollick (first edition) – Summary chapter 7

Concepts are mental representations of classes of items (e.g: dogs). Imagery is the mental representation of sensory properties of objects, experiences as like perceiving the object but with less vividness than in reality. There are different approaches to concepts.

The definitional approach looks at the definition of an object in order to form a concept. The concepts are based on the definition of the word. This approach looks for well-defined concepts. The main problem with this approach is that most everyday concepts are not so well defined.

The prototype approach looks at the most typical of a ‘family’ of concepts which represents the other concepts. Typicality is the extent to which an object is representative of a category. Members of a category share a family resemblance. This is the tendency for members of a category to be similar to each other but without having any characteristic in common to all of them. The more an item of a category has a family resemblance, the more typical it is deemed to be. The item in a category that has the highest overall family resemblance to the other category members is the prototype of that category. The prototype is an ideal example that best represents a category. The prototype does not have to exist. It is the statistically average member of the category. Categories and concepts typically form into hierarchies. Lower level categories are nested within higher-level categories. The mid-level category is the basic level of categorization. These are categories formed of items that are highly similar and at an intermediate level in a concept hierarchy. The problems with the prototype approach are that some objects are more readily categorized as something, even though it looks more like a different prototype and some things don’t have prototypes, such as rules or beliefs. Ad hoc categories are categories formed of items that meet a given goal. The family resemblance does not work for ad hoc categories.

The exemplar-based approach proposes that categories are represented purely by stored examples or instances and each example Is linked to the category name. If a new item’s similarity to already known items is above a certain threshold it becomes a member of that category. The exemplar approach readily represents variability within a category, which the prototype approach does not.

The theory/knowledge-based approach uses knowledge in order to categorize items. It includes causal information and causal knowledge is used in order to categorize items.

Essentialism is the view that all members of a given category share some key property. This does not have to be something that can be seen from the outside (e.g: a bird without feathers is still a bird). Barton argued that there are different types of concepts which may have different forms of essential properties:

1. Nominal concepts
   These are concepts which have clear definitions. The essential part is easy to locate here (e.g: triangles are three-sided closed figures).
2. Natural kind concepts
   These are concepts that are commonly identified as naturally occurring (e.g: cats, rainy days).
3. Artefact concepts
   These are concepts that are human-made objects and are generally defined in terms of their function (e.g: laptops).

Barton asked participants to imagine three types of transformation of natural kind and artefact categories: functional, physical and molecular. The artefact concepts were more prone to changing categories when functional changes occurred and the natural kind concepts were more prone to changing categories when molecular changes occurred. The sensory-functional distinction states that for some categories perceptual features were critical and for others functional characteristics were critical.

Barsalou proposed the view that concepts are grounded in modality-specific systems for perception, action and introspection with no need for amodal abstract symbols. This view is called grounded representations, which are representations that involve sensory-motor codes. Amodal representations are representations that are abstract and do not involve any sensory codes. The role of simulation, the extended re-enactment of previous experience is important in cognition according to Barsalou. Re-enactment is the partial repetition of the internal processes involved in previous perceptions or actions. The larger the property that a participant has to imagine, the slower the verification. Switching from one modality to another also slows verification. The brain areas that are active when objects are perceived are also active when the object’s name is being said.

Imagery is imagining a certain concept and see it in the mind’s eye. It replicates actual experiences, but it is less vivid. Visuospatial processing is the mental manipulation of visual or spatial information. Imagery and perception draw on the same mental and neural resources. The self-reported vividness of imagined items reduces because of a tapping task, but not because of a counting task. The further away some imagined things are, the longer the response time is. Images encode relative distance with some accuracy. Difference judgements between symbolically presented items are made more easily for items that are indeed widely different in reality is known as the symbolic difference effect. Mentally rotating items takes about as long as really rotating the physical item.

Pylyshyn criticised the scanning of mental images because it could be very prone to bias. He argues that the experience of imagery has no real causal role in cognition. It is a by-product of the machine’s operation according to him but does not contribute to the machine’s functioning. The Gestalt theory of perception states that ambiguous figures cause unstable representation that resolves themselves into alternating representations. Images are not exactly like pictures but rather always have some fixed interpretation on which they are based.