In our recent CIKM paper An Eye-tracking Study of User Interactions with Query Auto Completion (QAC), we looked at how searchers examine and interact query completions, and what this tells us about measuring QAC ranking quality. Accurately interpreting user interactions would allow us to optimize search for each individual user. However, measuring performance is a real bottleneck, because searcher behaviour itself is affected by the searcher’s previous experience, expectations, and the search engine.
Here’s an example video that shows how searchers examine QAC:
For full details, take a look at the paper here.