Cognitive Aspects Affecting Human Performance in Manual Assembly

This paper concerns the handling of information in assembly work environments. Several studies involving both literature reviews, case studies and observations were conducted to find factors that affect human performance in manual assembly. The main experiment with 36 subjects used a mixed method design with a quantitative study, including time and errors as dependant measures, a qualitative study, including workload ratings, and a questionnaire. The experiment involved the assembly of a pedal car and the components were presented using structured kits, unstructured kits and material racks. Assembly information was presented as text & component numbers or photographs, and situations with and without component variation were considered. Among the results it was found that assembly times and workload ratings were lower when using a kit, whereas using a material rack resulted in perceived decreased workflow and increased stress and frustration. Assembly times and workload ratings were lower when using photographs, whereas using text and numbers increased mental workload.