In the feature condition, the subject should still be able to respond immediately, even when the number of distracter items in the display is increased. As opposed to the conjunctive search condition, where selective use of attention is required, therefore, the reaction time should increase as the number of distracter items in the display increases.
Dependent Variable
This experiment is interested in measuring the reaction time (how long it takes the subject to find and respond to a particular item in the display or when they are certain that the specific item is not in the display), to see if it will increase with background complexity or more distracters in the display.
Independent Variable
The number of distracters is manipulated by surrounding the target with distracters that either did or did not share the task irrelevant features with the target.
Group Results
Generally, results showed a serial search for conjunction conditions and a parallel search for feature conditions for all subjects. For all subjects, target-present trials were responded to at a considerably faster rate than absent trials. The pattern of reaction was generally better related to the total number of distracters across all planes. However, this pattern was influenced by the presence or absence of the target in the display. For all subjects reaction times in absent trials strongly reflected the total number of distracters while those for the present trials did not. Figure 1 (in the appendix section) shows groupings in absent trials and the gradual decrease of reaction times for the conditions where the target was present.
Conclusion
The signal detection theory, insinuates that we can process and perceive many things at a specific time. However, when we participate in a visual search task, that requires attention to be divided amongst the amount of information to be searched, it increases the risk of error at the decision level (Eckstein, 1998).
In 2001, both Dobkins and Bosworth studied the effects of cueing on motion processing. The results obtained from their study imply, that humans have the ability to process multiple stimuli at a given time. Dobkins and Bosworth go on further to say that they agree with Pashler (1998), that we can process many things simultaneously, but we can also selectively choose which objects that will be processed. These results also correspond with functional magnetic resonance imaging research, signifying that the amount of attention required for a particular task will balance out the resources needed for processing information that isn’t relevant to the task (Rees & Lavie, 2001). Dobkins and Bosworth conclude in their report, that attention reduces cognitive resources reserved for distracters and enhances processing.
APPENDIX
Group Results
Data summary for experiment Visual search 25-Mar-03 9:57:57 PM
Results are based on data from 135 participants.
Figure 1
