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Users can filter the feed items displayed to them, to look at find what is currently of the most of interest to them currently. We gave Hubbub allows users the ability to filter by service, by content text, by tags, or by existence of hyperlinks. This interface gives users a fair amount of power, but it was also the trickiest was difficult to design for good learnability. When showing testing our paper and computer prototypes to users, the filter interface tended to be the most troublesomewas the hardest for users to use. In particular, users were unsure how the different criteria composed (boolean "and" or "or"?) and some were confused about the function of the service icons or the text box.
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