The effect of proximity, Tall Man lettering, and time pressure on accurate visual perception of drug names

Amy Irwin, Kathryn Mearns, Margaret Watson, Jim Urquhart

Research output: Contribution to journalArticlepeer-review

26 Citations (SciVal)


OBJECTIVE: The aim of this study is to assess the effect of proximity and time pressure on accurate and effective visual search during medication selection from a computer screen.

BACKGROUND: The presence of multiple similar objects in proximity to a target object increases the difficulty of a visual search. Visual similarity between drug names can also lead to selection error. The proximity of several similarly named drugs within a visual field could, therefore, adversely affect visual search.

METHOD: In Study 1, 60 nonpharmacy participants selected a target drug name from an array of mock drug packets shown on a computer screen, where one or four similarly named nontargets might be present. Of the participants, 30 completed the task with a time constraint, and the remainder did not. In Study 2, the same experiment was repeated with 28 pharmacy staff.

RESULTS: In Study 1, the proximity of multiple similarly named nontargets within the specified visual field reduced selection accuracy and increased reaction times in the nonpharmacists. Time constraint also had an adverse effect. In Study 2, the pharmacy participants showed increased reaction times when multiple nontargets were present, but the time constraint had no effect. There was no effect of Tall Man lettering.

CONCLUSION: The presence of multiple similarly named medications in close proximity to a target medication increases the difficulty of the visual search for the target. Tall Man lettering has no impact on this adverse effect.

APPLICATION: The widespread use of the alphabetical system in medication storage increases the risk of proximity-based errors in drug selection.

Original languageEnglish
Pages (from-to)253-266
Number of pages14
JournalHuman Factors : Journal of Human Factors and Ergonomics Society
Issue number2
Publication statusPublished - Apr 2013


  • Adolescent
  • Adult
  • Drug Labeling
  • Drug Packaging
  • Drug Storage
  • Female
  • Humans
  • Male
  • Medication Errors
  • Middle Aged
  • Reaction Time
  • Visual Perception
  • Young Adult


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