Is eye tracking the next step in usability testing?

In usability testing, eye tracking has been used to gain insight into human behavior that may not be available through observation or think-aloud protocols. HCI researchers have suggested that the eye movement measures of fixation duration and fixation frequency are related to cognitive processing ease/difficulty and search efficiency/inefficiency. This study investigates whether the connection between these eye movement measures and their respective cognitive activities can be confirmed through user self-reported data. The findings show that fixation duration and fixation frequencies are interdependent measures. Analysis of the self-reported data indicates that although users' responses are limited in what they reveal about cognitive processes, the responses generally confirm the eye movement measures.