How do results from a flanker task demonstrate that attention may be understood as competition for limited resources?

How do results from a flanker task demonstrate that attention may be understood as competition for limited resources?

Generally speaking, it is a task in which participants are told to attend to specific stimuli and ignore any other. For example, they may be told to press "z" when A or B appears as a stimulus, and "m" if C or D is presented. The conducted research looks as follows:

1. B A B (press z) --> compatible flankers "B" --> fastest response

2. C A C (press z and m) --> incompatible flankers "C" --> slowest response to target

3. X A X (press z) --> neutral flankers "X" --> intermediate response

The results suggest that although told to attend only to specific stimuli, participants also process the flankers. When they are compatible (1) no further cognitive resources are used up. In condition (2) incompatible flankers elicit a response that is different from the target (press "m") and therefore this requires further cognitive resources. Hence, it takes longer to respond correctly. Condition (3) uses up more cog. resources than (1) because the flankers are not compatible with the appropriate response, yet they do not require any additional response (neutral) and therefore do not take as long, as condition (2).