Reference no: EM13338102

A hypothetical experiment is run using a visual search task where the "odd-one-out" is to be found within a background of 20 distractor items that are identical to each other apart from a variation in their size. Each stimulus array is displayed on the computer screen until a response is made. The instructions simply tell the participants to touch the stimulus that differs from all the others in the array (ignoring size). For each trial, reaction times (RTs) are measured from the time the stimulus array is presented until contact is made to the touch- sensitive screen.
Six blocks of 60 experimental trials are run. The position and identity of both the target and the set of distractors change randomly from trial to trial. The target is always a letter, either upper-case or lower-case, and the distractors are of three different types:
Condition A: The same letter as the target, but in the other case.
e.g.: finding b among B's
Condition B: A different letter to the target in the other case.
e.g.: finding b among H's
Condition C: Non-letters.
e.g.: finding b among 5's
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There are an equal number of trials for each condition randomly mixed within each block (i.e., 20 for each condition per block), and an equal number of upper-case targets (as illustrated in the examples above) and lower-case targets (not illustrated). The experiment is designed so that, across all trials, the similarity between the target and its distractors is equated between all three conditions in terms of physical features.

1. In the Week 8 tutorial, you were shown a model of the cognitive processes that might be involved in performing a same-different letter-matching task. Such a task is different to the odd-one-out task described here and, therefore, the two tasks require rather different processing. Give a theoretical account of the cognitive processes that might be involved in performing the odd-one-out task and use this to explain the following hypothetical results:

Mean RT to Condition A is longer than to Conditions B which, in turn, is longer than to Condition C.
Use a diagram only if you think it makes your answer clearer. (Worth 10%)

2. Would you expect the difference in RTs between the three conditions to vary across the blocks of trials? That is, is there likely to be an interaction between the Condition and Block factors? Explain your answer.
(Worth 5%)

3. Suppose that, instead of touching the odd-one-out target on the screen, participants are asked to name the letter that is different to all the other stimuli as quickly as they can, and the latency to respond is measured. How do you think the pattern of results described in Question 1 might change, if at all, and why?
(Worth 5%)

Note that there is no single right answer to these questions. What we are therefore looking for is clear logical thinking that makes sense in the light of the content covered in the Week 8 and Week 9 tutorials. Neither is there any hard- and-fast format for presenting your answers. Just present them in the way you think would be clearest to the reader.
The use of references is unnecessary. You should only refer to the literature if, for some reason, you want to state a fact that needs to be justified from past research.