This protocol helps researchers investigate distraction while multitasking in a visual search environment. For example, say you're grocery shopping, and you're looking for a red pepper. When you apply attention to this task, you enhance the processing of all similar items such as everything that's red.
As a result, everything red will capture your attention and slow down your search. Now, suppose you have more than one item on your grocery list, such as a red pepper and a yellow pepper. To look for more than one item at a time, the processing of information relevant to both items will be enhanced.
How does distraction effect multitasking search? Our protocol addresses this question. To investigate this we asked participants to search a rapidly changing central display of color letters and identify all the letters that appear in either of two particular target colors.
Occasionally, the gray letters in the left and right displays will change colors, which is distracting. In this slowed down example, there's an orange U target and a green X target. This method can help answer key questions about visual attention, such as how search goals are maintained and used in memory and what are our limitations of multitasking.
A major advantage of this technique is that the task produces large effects, providing researchers with the flexibility of measuring nuance aspects of distraction. This technique extends towards applied questions such as how do radiologist search medical images for abnormalities, or how security officers search bags for contraband. Demonstrating the procedure will be Jamie Jasina and Ariel Kershner, undergraduates from the Attention, Memory, and Cognition Laboratory.
Before beginning the experiment, select the trial types and the number of trials within each type. For example, in Target Alone trials the target appears without any recent color changes to letters in the periphery. In Distractor Alone trials, a letter in the periphery changes to a target color, but no target appears subsequently in the central display.
In Non-target colored distractor trials, a colored letter appears in the periphery just before a target appears centrally, but the distractor is not target colored. In same target colored distractor trials, the colored peripheral item appearing ahead of the target is the same color as that target. In different target colored distractor trials, the colored peripheral item appearing ahead of the target is also target colored, but is not the same color as the target on that trial.
Now, select the target distractor lag lengths in each trial type that contain the distractors and targets. And select the target, distractor, and central filler colors for the letters, insuring that target colors are not adjacent on the color wheel. When the task is designed and programed, seat the participant 57 centimeters away from the monitor using a chin rest to enforce this viewing distance, and secure the monitor in a fixed location as necessary.
Open the software, navigate to the experiment folder, and enter the experiment script into the command window. Enter the parameters, such as the date and the participant number, and help the participant through the instructions. Supervise the participant during the experiment to ensure that a uniform viewing distance from the monitor is maintained, that the task is being properly completed, and that the participant is not falling asleep or becoming distracted.
Remind the participant of the response keys, to slow and consider which response to make after identifying a letter, and that the response will be recorded as correct even if it does not occur immediately. Encourage the participant to take breaks as necessary. This task is very difficult with performances averaging about 75%correct.
Be sure to encourage your participants not to become discouraged if they're making many mistakes. When the program concludes, debrief and dismiss the participant. Performance on Target Alone trials is equally good whether participants are looking for one or two targets at the same time.
When a peripheral item appears that is not target colored, this is not distracting. When the peripheral distractor and the target are the same color, performance drops as the target color distractor captures attention. The difference in performance between non-target colored trials and same target colored trials is considered contingent attentional capture.
When a target colored distractor is not the same color as the subsequent target on that trial, performance plummets. This set specific capture effect is two to three times as large as contingent attentional capture. Set specific capture occurs when an irrelevant stimulus that is related to one goal captures attention and the ability to identify a target matching the other goal is impaired due to a temporary change in how the goals are represented in memory.
As well as being so costly, set specific capture takes longer to recover from than does contingent attentional capture. While attempting this procedure, it's important to provide feedback and encouragement. This procedure can be adapted to different stimuli such as images, to determine how distraction effects change when many goals are maintained.
Future studies could examine how we search for different features or concepts and may reveal mechanisms of attention and how they relate to memory and perception.
