Elsevier

Social Science & Medicine

Volume 57, Issue 10, November 2003, Pages 1939-1955
Social Science & Medicine

Effects of frequency and similarity neighborhoods on pharmacists’ visual perception of drug names

https://doi.org/10.1016/S0277-9536(03)00059-5Get rights and content

Abstract

To minimize drug name confusion errors, regulators, drug companies, and clinicians need tools that help them predict which names are most likely to be involved in confusions. Two experiments, carried out in the United States, examined the effects of stimulus frequency (i.e., how frequently a target name is prescribed), neighborhood frequency (i.e., how frequently prescribed are the “neighbors” of the target name), and neighborhood density (how many names are within a fixed distance of the target name) on the probability of pharmacists making an error in a visual perceptual identification task. In both experiments, the task was to correctly identify a series of blurry drug names after a 3 s presentation on a computer monitor. In the first experiment, 45 pharmacists viewed 160 typewritten names, incorrectly identifying 60.6% of them. Random effects regression revealed a significant beneficial effect of stimulus frequency and a detrimental effect of neighborhood density. Significant two-way interactions were observed between stimulus frequency and neighborhood density and neighborhood frequency and neighborhood density. In the second experiment, 37 pharmacists viewed 156 handwritten drug names, incorrectly identifying 45.7%. Random effects regression revealed significant main effects of stimulus frequency and neighborhood density. These were contained within a significant three-way interaction: The interaction between stimulus frequency and neighborhood density was present at high but not low neighborhood frequency. Objectively measurable frequency and neighborhood characteristics have predictable effects on errors in pharmacists’ visual perception. Organizations that coin and evaluate drug names, as well as hospitals, pharmacies, and health systems, should consider these characteristics when assessing visually confusing names.

Introduction

Recent estimates suggest that medical errors of all types may cause the death of between 44,000 and 98,000 hospitalized patients in the United States each year (Kohn, Corrigan, & Donaldson, 2000). Errors involving medication cause the death of one person every day in the US, and injure more than a million more each year (US Food and Drug Administration, 2001). Confusions between drug names that look and sound alike account for between 15% and 25% of reported medication errors in the US (US Pharmacopeia (1995), US Pharmacopeia (1996), US Pharmacopeia (2001)). Similarity between drug names can cause errors in short-term memory as well as in visual and auditory perception (Brodell, Helms, KrishnaRao, & Bredle, 1997; Lambert, Chang, & Lin, 2001b; Lambert, Chang, Lin, & Gupta, 2000; Lambert, Lin, Gandhi, & Chang, 1999; Luce & Pisoni, 1998; Luce, 1959). This investigation examined the effect of similarity and prescribing frequency on pharmacists’ ability to accurately identify blurry, briefly presented, handwritten and typewritten drug names. Two research questions provided the motivation for the experiments that follow:

  • (1) To what extent is a pharmacist's ability to identify a target drug name affected by the prescribing frequency of the target, the number of names similar to the target, and the prescribing frequency of the similar names?

  • (2) To what extent do the characteristics in Q1 have different effects depending on whether the drug name is handwritten or typewritten?

Section snippets

Activation-competition models of visual perception

The “interactive activation” framework has been very influential in the development of cognitive psychology theories of visual word recognition, following a seminal formulation of this approach by McClelland and Rumelhart (McClelland & Rumelhart, 1981; Rumelhart & McClelland, 1982). In such a model, words are represented in memory as networks of nodes connected by excitatory and inhibitory links. The nodes are typically arranged in a hierarchy of levels. Lower level nodes detect particular

Design

This experiment was designed to examine the effect of prescribing frequency, neighborhood frequency and neighborhood density on the probability of a pharmacist making an error in a visual perceptual identification task. Participants viewed a series of noise-masked, typewritten drug names as they were briefly presented on a computer monitor. The task was to correctly identify the presented name by typing it into a provided text box. All experiments were approved in advance by the local

Design

The design of Experiment 2 was identical to that used in Experiment 1 except that in this experiment, handwritten drug names were used as stimuli instead of typewritten names (Brodell et al., 1997). This experiment also used a slightly different type of degradation (described below).

Participants

Participants were 37 licensed, practicing, community pharmacists recruited from the exhibit halls and corridors of the 2000 annual meeting of the National Community Pharmacists Association in San Antonio, Texas. All

General discussion

Drug name confusions are a persistent source of medication errors and an ongoing threat to patient safety. In spite of all that has been written and all the remedial steps that have been taken recently, new pairs of confusing names continue to appear regularly (Institute for Safe Medication Practices, 2002). One way to minimize the incidence of these errors is to equip decision-makers in the pharmaceutical industry and the FDA with tools to make better name-approval decisions. Such tools should

Acknowledgements

This research was supported in part by the National Patient Safety Foundation and by the Latiolais Leadership Fund of the Ohio State University. The authors acknowledge the assistance of Bill Brewer, Mike Cohen, Gary Dell, Robert Gibbons, David Lambert, Eric Lambert, Robert Lee, Swu-Jane Lin, Paul Luce, Susan Proulx, Don Rucker, and Gordon Schiff. We are also indebted to the volunteer participants from the American Pharmaceutical Association and the National Community Pharmacists Association.

References (47)

  • J Grainger et al.

    Visual word recognitionModels and experiments

  • J Grainger et al.

    Orthographic processing in visual word recognitionA multiple read-out model

    Psychological Review

    (1996)
  • J Grainger et al.

    Neighborhood frequency effects in visual word recognitionA comparison of lexical decision and masked identification latencies

    Perception & Psychophysics

    (1990)
  • L.L Havens et al.

    The effect of competition on visual duration threshold and its independence of stimulus frequency

    Journal of Experimental Psychology

    (1963)
  • Hedeker, D. (1999). MIXOR/MIXREG Website [HTML page]. University of Illinois at Chicago. Available:...
  • D Hedeker et al.

    A random-effects ordinal regression model for multilevel analysis

    Biometrics

    (1994)
  • D.W Hosmer et al.

    Applied logistic regression

    (1989)
  • D.H Howes et al.

    Visual duration threshold as a function of word probability

    Journal of Experimental Psychology

    (1951)
  • Institute for Safe Medication Practices. (2002). ISMP medication safety alert! (7(7)). Huntingdon Valley, PA: Institute...
  • A.M Jacobs et al.

    Models of visual word recognition—Sampling the state of the art

    Journal of Experimental Psychology: Human Perception and Performance

    (1994)
  • G Keppel

    Design and analysisA researcher's handbook

    (1991)
  • D.G Kleinbaum

    Logistic regressionA self-learning text

    (1994)
  • Kohn, L. T., Corrigan, J., & Donaldson, M. S. (Eds.). (2000). To err is human: Building a safer health system....
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