Experimenter effects on behavioral test scores of eight inbred mouse strains under the influence of ethanol

Behav Brain Res. 2014 Oct 1;272:46-54. doi: 10.1016/j.bbr.2014.06.017. Epub 2014 Jun 13.


Eight standard inbred mouse strains were evaluated for ethanol effects on a refined battery of behavioral tests in a study that was originally designed to assess the influence of rat odors in the colony on mouse behaviors. As part of the design of the study, two experimenters conducted the tests, and the study was carefully balanced so that equal numbers of mice in all groups and times of day were tested by each experimenter. A defect in airflow in the facility compromised the odor manipulation, and in fact the different odor exposure groups did not differ in their behaviors. The two experimenters, however, obtained markedly different results for three of the tests. Certain of the experimenter effects arose from the way they judged behaviors that were not automated and had to be rated by the experimenter, such as slips on the balance beam. Others were not evident prior to ethanol injection but had a major influence after the injection. For several measures, the experimenter effects were notably different for different inbred strains. Methods to evaluate and reduce the impact of experimenter effects in future research are discussed.

Keywords: Accelerating rotarod; Balance beam; Grip strength; Laboratory environment; Motor coordination; Open field activity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Central Nervous System Depressants / administration & dosage*
  • Ethanol / administration & dosage*
  • Exploratory Behavior / drug effects
  • Exploratory Behavior / physiology
  • Female
  • Housing, Animal
  • Male
  • Mice, Inbred Strains
  • Motor Activity / drug effects*
  • Motor Activity / physiology*
  • Odorants
  • Random Allocation
  • Reproducibility of Results
  • Research Design*
  • Research Personnel*
  • Rotarod Performance Test


  • Central Nervous System Depressants
  • Ethanol