Our mental 'inbox' of working memory is ... constrained ... Several decades of research have indicated that our capacity to hold information "in mind" for immediate use is limited to a mere three or four items.More information is not better. To be most productive on a task, we want to maximize our ability to filter for relevant information, not maximize our ability to acquire information.
There are at least two primary explanations for this severe limitation in working memory capacity. First, it could be that working memory capacity is essentially determined by storage space, and that some people have larger "hard drives" than others do.
The alternative explanation is that capacity depends not on the amount of storage space but on how efficiently that space is used. Thus high-capacity individuals might simply be better at keeping irrelevant information out of mind, whereas low capacity individuals may allow more irrelevant information to clutter up the mental inbox. High-capacity individuals may just have better spam filters.
Some of our recent work has provided evidence favoring this mental spam filtering idea. In one experiment... high-capacity people were excellent at controlling what information was represented in working memory: They let in information about relevant objects but completely filtered out irrelevant objects. Low-capacity individuals, by contrast, had much weaker control over what information entered the mental "in box"; they let in information about both relevant and irrelevant objects roughly equally.
Surprisingly, these results mean that we found that low capacity people were actually holding more total information in mind than high capacity individuals were -- but much of the information they held was irrelevant to the task.
This result is not surprising, but it does nicely frame the problem for those of us working in information retrieval. Not only is precision more important than recall, not only should we help people filter data and focus their attention, but also we may want to explicitly help people form and retain a working set of knowledge to apply to their task.
For example, search engines are increasing their support for re-finding, helping people remember and return to information found in the past. This usually is done as a web history, not an explicit representation of a past working set of knowledge, but it does help people build a working set, get back to items that may have dropped out of their working set, and swap back in the working set for an old task to which they are returning.
More generally, I think it is useful to think of searchers as skimming and filtering the information on pages as they try to build a small set of relevant information for their task. This may suggest methods we might consider to filter and help focus attention, such has highlighting parts of a page that are particularly likely to be useful, explicitly attempting to determine what may be distracting on a page for specific types of tasks and reducing those distractions, and carrying information and history across pages as people work on their tasks.
[SciAm article found via Mark Thoma]