For this task, subjects are shown four plants, two of which are healthy and two of which are unhealthy. After hearing the individual treatments each plant has received (e.g., type of plant food and amount of water), participants are asked to decide the health of a plant they cannot see based on a description of its treatment (for further discussion, see the article by Nixon, pp. 97–103). In addition, the subjects are asked to describe how they know that the plant is healthy or unhealthy; in other words, they must identify the relevant variable related to the plant’s outcome.
