Self Paced Reading Example: Critical Items

Recall the 2x2 example design we described earlier:

Example 2x2 Design
Figure 1: A 2x2 design, crossing contextual predictability (high vs. low) with word frequency (high vs. low).

In this design, a critical item consists of four stimuli, one for each of our conditions.

We refer to the entire quadruple above as one critical item. So, for a typical experiment we will have to make many such critical items. Typically, self-paced reading experiments contains 6-8 times as many critical items as they contain conditions. Why do you think this is the case? Think about it for a moment and then quiz yourself.

1. Why do you think the recommended number of critical items is function of the number of conditions?

2. How many critical items should our example experiment have?

3. Can you think of a reason why it might be better to have 8 times as many items as conditions, rather than 6 times as many items as conditions?

4. Can you think of a reason why it might be better to have 6 times as many items as conditions, rather than 8 times as many items as conditions?

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