The geneis and mechanism of human error in accidents resulting latent danger

Six accidental cases caused by overlooking latent environmental danger were analyzed and the geneses and mechanism of the human error involved were discussed. In all cases detection of the danger was easy or indications by some warning were distinct. In a typical case, a lineman, after cleaning the insulators of a suspended line, proceeded toward the danger zone of another line charged with current on reaching the ground. He disregarded the warning flag, and received a shock and fell to the ground. It was also common in all the other cases that victims were conducting relatively easy or habitual activities and responded, being almost unaware of the unusual physical characteristics of the environment, to its more apparent aspects. These errors were relevant to experimental results by the author that subjects had great difficulty in identifying the rule of presentation of signal figures if the key item and the rule, either serial or positional, were different from foregoing trials. It is suggested that an individual fails to see an external object that has little function value in regard to the content of the current behavior under influence of personal habitual experiences and the theories of human error need to be reconstruct as the basis of ecological knowledge about them.