title: Thinking aloud influences perceived time.
abstract: OBJECTIVE
  We investigate whether thinking aloud influences perceived time.
  
  
  BACKGROUND
  Thinking aloud is widely used in usability evaluation, yet it is debated whether thinking aloud influences thought and behavior. If thinking aloud is restricted to the verbalization of information to which a person is already attending, there is evidence that thinking aloud does not influence thought and behavior.
  
  
  METHODS
  In an experiment, 16 thinking-aloud participants and 16 control participants solved a code-breaking task 24 times each. Participants estimated task duration. The 24 trials involved two levels of time constraint (timed, untimed) and resulted in two levels of success (solved, unsolved).
  
  
  RESULTS
  The ratio of perceived time to clock time was lower for thinking-aloud than control participants. Participants overestimated time by an average of 47% (thinking aloud) and 94% (control). The effect of thinking aloud on time perception also held separately for timed, untimed, solved, and unsolved trials.
  
  
  CONCLUSIONS
  Thinking aloud (verbalization at Levels 1 and 2) influences perceived time. Possible explanations of this effect include that thinking aloud may require attention, cause a processing shift that overshadows the perception of time, or increase mental workload.
  
  
  CONCLUSIONS
  For usability evaluation, this study implies that time estimates made while thinking aloud cannot be compared with time estimates made while not thinking aloud, that ratings of systems experienced while thinking aloud may be inaccurate (because the experience of time influences other experiences), and that it may therefore be considered to replace concurrent thinking aloud with retrospective thinking aloud when evaluations involve time estimation.
authors: Morten
authors: M
authors: Hertzum
authors: Kristin Due
authors: KD
authors: Holmegaard
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D013647:Task Performance and Analysis; D013850:Thinking / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*; D014705:Verbal Behavior / Q000502:physiology*; D055815:Young Adult