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Task: Participants were asked to track 4 objects from a field of 8 objects. The target objects were cued by white outline frames. At the end of the motion period, all objects changed into white disks. Subjects had to click on the four target disks. After their response, the correctly clicked balls are highlighted in green. (In the demo here the target balls are highlighted in green after a pause).
The actual displays in the experiment subtended 21x21 degrees, several times bigger than what's shown in the movie. In addition, the motion speed shown in the demons is an approximation to the actual speed. In some experiments the duration of the motion phase was randomized, so subjects could not predict when a trial would end.
Experiment 1: Condition 1: Homogeneous identities. All objects have the same color. Click here to view homogeneous.mov (File size: about 800KB)
Experiment 1: Condition 2: All-unique identities. The eight objects have unique colors. Click here to view Heterogeneous.mov
Experiment 1: Condition 3: Four-unique identities. Two targets have color 1, two other targets have color 2, two distractors have color 3, and two other distractors have color 4. Click here to view Four-unique identities.
Experiment 1: Condition 4: Paired-four. The four targets have unique colors and the four distractors have unique colors, but one target has the same color as one of the distractors. Thus, the target and distractor are "paired" in color, with 4 total colors used on a display. Click here to view paired-four.mov
Experiment 1: Condition 4: Paired-two. Two targets and two distractors are in color 1, and the other targets and distractors are in color 2. Thus, targets and distractors have "paired" colors with a total of 2 colors used on a display. Click here to view paired-two.mov
Experiment 1 Results: Performance is higher in the all-unique and four-unique identities conditions than the homogeneous condition. Performance in the paired-four and paired-two conditions is worse than the homogeneous condition when all trials are randomly intermixed, and not different from homogeneous when trials are tested in separate blocks.
Experiment 3a: Condition 1: Homogeneous identities, color-changing (260ms/change). Items change colors once every 260msec. However, all items have the same color at any given moment. Click here to view homogeneous-changing-color260.mov.
Experiment 3a: Condition 2: All-unique identities, color-changing. Items change colors once every 260msec. However, at any given moment all items have unique colors. Click here to view All-unique-changing-color.mov
Experiment 3a: condition 3: T-D paired identities, color-changing. Items change colors once every 260msec. However, at any given moment the targets are all unique and the distractors are all unique, but a target is the same as one of the distractors. Click here to view paired-changing-color.mov
Experiment 3a Results: When colors change very 260msec, the all-unique condition is tracked at lower accuracy than the homogeneous condition. When colors are maintained throughout a trial, the all-unique condition is tracked at higher accuracy than the homogeneous condition.
Experiment 3b: Condition 1: Homogeneous identities, color changing 500ms/change. Items change colors once every 500msec. All items have the same color at any instant. Click here to view homogeneous-changing-color-500ms.mov
Experiment 3b: Condition 2: All-unique identities. color changing 500ms/change. Items change colors once every 500msec. All items have unique colors at any instant. Click here to view All-unique-changing-color-500ms.mov
Experiment 3b: Condition 3: Homogeneous identities, color changing 1000ms/change. Items change colors once every 1000msec. All items have the\ same color at any instant. Click here to view homogeneous-changing-color-1000ms.mov
Experiment 3b: Condition 4: All-unique identities. color changing 1000ms/change. Items change colors once every 1000msec. All items have uniq\ ue colors at any instant. Click here to view All-unique-changing-color-1000ms.mov
Experiment 3b results: Similar to Experiment 3a, changing colors removed the advantage of tracking uniquely colored objects, even when the change occurred at a relatively slow rate. There was no difference between 500ms and 1000ms change rate.
Note: Motion speed used in the next three demos in the actual experiment is much faster than the movies shown below.
Experiment 4: Condition 1: Tracking homogeneous objects while maintaining a concurrent color memory load. Participants track 4 cued targets that are identical to the nontargets. At the same time, they monitor the central color patches and count the number of times a color change occurs from one presentation to another. This is a very demanding dual-task and you may need to watch the movie many times to get the correct answer (across the five presentation of color displays, there are 3 color changes from one presentation to the next). Click here to view homogeneous-load4.mov
Experiment 4: Condition 2: Tracking unique objects while maintaining a concurrent color memory load. Participants track 4 cued targets that are all unique from the nontargets. At the same time, they monitor the central color patches and count the number of times a color change occurs from one presentation to another. Click here to view all-unique-load2.mov In the actual experiment, the central color task can have a load of 0, 1, 2, or 4. In this demo, across the five presentation of colors, there are 2 color changes from one presentation to the next.
Experiment 4: Condition 3: Tracking T-D color paired objects while maintaining a concurrent color memory load. Participants track 4 cued targets that have paired identity to the four nontargets. At the same time, they monitor the central color patches and count the number of times a color change occurs from one presentation to another. Click here to view paired-load1.mov (There is just 1 color change in this demo).
Experiment 4 results: Color memory was impaired when participants tracked uniquely colored objects, suggesting that visual working memory was used to track uniquely colored objects.
For more information, contact Tal Makovski at tal.makovski@gmail.com. A copy of the paper can be found here.
