Statement of the problem.—It was the purpose of this study (a) to investigate the effect of error density (level, rate, or number of errors) on checking efficiency in a proofreading situation under normal conditions, i.e., comfortable working conditions without stress; and (b) to investigate the effects of experience in detecting errors at one level of density on the detection of errors at a later time in which the density level has been changed. This would show if there is a relationship between signal detection and habituation as well as signal density, and would reflect the possible role of learning in the detection of error signals
