Defining-attribute (classical) theories of categorisation suggest that categories have concrete boundaries defined by a fixed set of attributes of equal importance. However, typicality studies (e.g., Barr & Caplan, 1987; McCloskey & Glucksberg, 1979) have demonstrated that categories actually have fuzzy boundaries and that people rank members of categories according to how typical they are. This has lead to the theory that each category has a prototype; an abstract, cognitive representation of an ideal category member informed by the characteristic attributes that category-members share in varying degrees (Rosch & Mervis, 1975). Assuming prototype theory is correct, category-members with high resemblance to the prototype should be accurately recognised more quickly than ones that have low resemblance to the prototype.
Research Question (RQ) 1: Will participants take longer to accurately categorise atypical cities than typical ones?
Hybrid theories have combined the two approaches described above by suggesting that categories have both defining and characteristic features (e.g., Smith, Shoben, & Rips, 1974). According to Sternberg & Smith (1988), characteristic (prototype) properties are less diagnostic (and therefore less useful) than defining properties but are more commonly used because they are more readily available. Therefore, the greater people rely on prototypes for categorisation, the more errors they should make.
RQ2: In the absence of defining attributes, how effectively are participants able to accurately categorise atypical cities?
Method
Design: A within-subjects design was used. The independent variable (typicality of cities) had three levels: typical city, atypical city and non-city. Participant reaction time (ms) was the dependent variable.
Participants: 10 post-graduate psychology students at Leeds Metropolitan University.
Procedure: 51 settlements in England were equally divided into three groups: typical cities (e.g., Manchester); atypical cities (e.g., Brighton and Hove) and non-cities (e.g., Scarborough). Atypical cities were cities that lacked the characteristics people commonly associate with cities (Beckett, 2001). Participants were presented with the name of an English settlement and instructed to press “1” on a computer keypad if they thought it was an English city and to press “2” if they thought it was not an English city.
Measures: A desktop PC running E-prime software (Psychological Software Tools, Inc., Sharpsburg, PA) was used to present stimuli individually in a random-order and to record reaction times.
Results
A repeated-measures t-test revealed a highly significant difference in categorisation times for typical cities and atypical cities, t = -4.031, df = 9, p = .003.
| Mean | N | Std. Deviation | |
| Typical | 800.18 | 10 | 131.85 |
| Aypical | 988.58 | 10 | 226.89 |
| Filler | 969.00 | 10 | 234.08 |
Conclusions
- In general, participants took longer to accurately categorise atypical cities than typical cities which supports prototype theory and adds to the evidence against defining-attribute theory.
- English cities were chosen as the focus of the experiment because city status does not rely on any fixed criteria, thus encouraging participants to compare settlements with their ‘city prototype’. Atypical cities were, on average, incorrectly categorised 50% of the time. As there were only two options (city or not city) it is clear that participants could not categorise atypical cities any more effectively than chance alone predicted which strongly supports the theory that prototypes are an imprecise way of discerning category membership. Furthermore, 3 participants (unprompted) reported they attempted to recall whether a settlement had a cathedral or not in order to categorise it; thereby utilising an inaccurate prototype.
- Category membership maybe discerned in various ways depending on the type of category (Ashby & Maddox, 2005). It is suggested that future categorisation research takes into account that some categories are explicitly pre-defined, yet their boundaries are unclear (e.g., English city status). This may lead participants to categorise stimuli differently to how they would if they believed there was not an external right or wrong answer. Therefore, generalisation of these results is limited. A further limitation of this study is that, although the design encouraged prototype categorisation, it could be argued that participants may have utilised other methods (e.g., the exemplar approach).
- Categorisation is a process that allows people to apply past knowledge of a situation to recognise new instances of the situation; it enables classification, communication, reasoning and prediction. Therefore, the implications of this research span multiple domains and further research is recommended.
References:
Barr, R. A., & Caplan, L. J. (1987). Category representations and their implications for category structure. Memory & cognition, 15(5), 397-418.
Beckett, J. (2001). City status in the United Kingdom. History Today, 51(11), 18.
McCloskey, M., & Glucksberg, S. (1979). Decision processes in verifying category membership statements: Implications for models of semantic memory. Cognitive Psychology, 11(1), 1-37.
Rosch, E., & Mervis, C. B. (1975). Family resemblances: Studies in the internal structure of categories. Cognitive Psychology, 7(4), 573-605.
Smith, E. E., Shoben, E. J., & Rips, L. J. (1974). Structure and process in semantic memory: A featural model for semantic decisions. Psychological review, 81(3), 214.
Sternberg, R. J., & Smith, E. E. (1988). The Psychology of Human Thought: Cambridge University Press.