Here we tease apart where we attend from where we look when we search for targeted online information. We also examine how we block out information that distracts us from reaching our target. Using a unique dual task method, we test such cognitive mechanisms to evaluate their role in searching for online information:
Dual task method:
In our main search task, subjects look for and then select, with their mouse, target icons on a computer screen.
Immediately after selecting the target icons (with a mouse-click), a “probe-dot” may appear on a target, on a non-target (distractor) item, or on the surrounding background. Participants press a key if they detect a dot is present.
This probe-dot detection task assesses if participants are taking in information as they perform the search task. Inability to detect the dot is a signature of attentional inhibition. Importantly, inhibiting a distracting item that is close to a target benefits a user’s ability to detect a target item.
This dual task method reveals useful information about the cognitive mechanisms used in search but also the usability and effectiveness of UI designs. We learn:
How accurate and fast subjects are in finding and selecting icons on the computer screen,
Whether participants inhibit non-target information (as described above),
The amount of time & how often people look at selected vs. non-selected icons (i.e., fixation duration & frequency).
Participants & Equipment:
40 undergraduate students participated in 2 Blocks of 90 trials
Eye-movements were recorded using an Eyelink 1000 eye-tracker.
Findings:
Detection of the probe dot is similar when it is located on a target item (T), or on a nearby background (B), but impaired when located on distracting icons (D). This suggests that distracting objects are inhibited (unlike the targets or surrounding background regions).
In the figure above, probe-dot accuracy is shown on the left & search response times (RTs) are shown on the right. Most relevant results are in probe-dot present conditions (on the right of the accuracy & RT figures above).
Detecting the probe-dot is most difficult (less accurate and slower search) when on a Distractor (D) than when on a Target (T) or Background (B).
Correctly detecting the probe-dot & search reaction time is similar for target and background suggesting no attentional inhibition occurs for both of these cases.
These results support an inhibitory mechanism used in search where users inhibit non-target distractor items (but surprisingly not background information). We also show effects on gaze patterns: while participants looked the longest at targets or the background (likely when trying to detect the probe dot), participants looked most frequently at distractor items.
Implications for UX research:
When non-target distractor items are close to target items they are inhibited making it is easy for participants to find the targets. Inhibition likely accounts for why web-users can effectively ignore advertisements embedded in web pages.
Where people look does not always correspond with search behavior (such as when people frequently fixate on distractors). At these times a covert-inhibitory form of attention is operating.
Rather than eye-movements, search speed & accuracy are more informative measures of web usability and where our attentional system is inhibiting information.
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