Categorization

Background

The structure of categories in the mind is an important domain of study within cognitive science. Eleanor Rosch describes the importance in “Principles of Categorization” (1978). See the below excerpt for why categories are important.

The first has to do with the function of category systems and asserts that the task of category systems is to provide maximum information with the least cognitive effort; the second has to do with the structure of the information so provided and asserts that the perceived world comes as structured information rather than as arbitrary or unpredictable attributes. Thus maximum information with least cognitive effort is achieved if categories map the perceived world structructure as closely as possible. This condition can be achieved either bv the mapping of categories to given attribute structures or by the definition of redefinition of attributes to render a given set of categories appropriately structured.

Methods

Question for the class: Look at the colors below. If I want to know how you would classify the colors below into either “blue” or “green” categories, how would I test this?

Five colors between green and blue that vary smoothly

Psychophysics

If I show you these colors over many trials, and I ask you to responsd with either green or blue, your responses will produce data that looks like the below figure.

The data here is the proportion of time that you respond “blue.” For the color that is clearly green, you respond “blue” 0% of the time, and for the color that is clearly blue, you respond “blue” 100% fo the time. For the colors in the middle, you respond “blue” some proportion of the time. For the color exactly in the middle, you respond “blue” about half the time.

No imagine that there is some factor that biases you so that you are more likely to perceive the colors as blue than green.

Question for the class: What would the data look like now?

The data have now shifted toward the left (dots and red line) relative to the original data (gray line).

Question for the class: What would the data look like if you were biased towards green?

The data have now shifted toward the right (dots and red line) relative to the original data (gray line).

This is one tool that researchers can use to determine how participants perceive categorial boundaries.

Inverse multiple dimensional scaling

Participants can also be asked to sort objects by their perceived similarity.

Researchers ask participants to arrange images by dragging and dropping them on a screen based on their perceived similarity. Image from Holler et al (2020).

Visual search

Participants can be asked to detect the location of an object in a visual search array as quickly as possible.

Example task for a visual search experiment. Image from Bahle et al (2021).