The first step in running an experiment is defining what you want to discover and how you will do so. This chapter presents an approach to experiments that begins by first defining a research question, and then basing the definition of the conditions, experimental objects, and tasks on that question. These elements will ultimately define the form of the experiment.

Several key concepts used throughout the book are introduced and defined in this chapter:

• The research question : a clear question that succinctly states the aim of the research;

• Conditions: the ideas of interest – these will be compared against each other;

• The independent variable: the set of conditions to be used in the experiment – there will always be more than one condition;

• The population : all the people who might use the idea; the sample: the set of people who will take part in the experiment;

• Generalisability : the extent to which experimental results can apply to situations not explicitly included in the experiment itself;

• Experimental objects : the way in which the ideas are presented to the participants – experimental objects embody the conditions so that they can be perceived;

• Experimental stimulus : the combination of an experimental object and a condition;

• Experimental tasks : what the participants will actually do with the experimental objects;

• Experimental trial : the combination of a condition, an experimental object, and a task.