Identifying the task variables that predict object assembly difficulty.
OBJECTIVE: We investigated the physical attributes of an object that influence the difficulty of its assembly. Identifying attributes that contribute to assembly difficulty will provide a method for predicting assembly complexity. BACKGROUND: Despite object assembly being a widespread task, there has been insufficient research into information processing and cognition during assembly. The lack of research means that the variables that affect the performance of procedural assembly tasks with illustration-only instructions are unknown. METHOD: In Experiment 1, seven physical characteristics (task variables) of assembly objects were systematically varied in a balanced fractional factorial and orthogonal design to create 16 abstract assemblies, which were assembled by 12 participants (6 men and 6 women aged 18-56). A second experiment (20 participants, 8 men and 12 women aged 18 to 52) involved scaled-down models of 8 real-world assemblies. RESULTS: A clear relationship between the task variables and assembly difficulty was found in both studies, and the regression model from the first experiment was able to predict the assembly difficulty timings in Experiment 2. CONCLUSION: The proposed task variables are associated with assembly difficulty, and the regression analysis has shown four of the task variables to be significant predictors of difficulty. APPLICATION: Applications of this research include the use of the regression model as a tool to evaluate the difficulty of assemblies or assembly steps defined by instructions. The task variables can also be used to produce guidelines to ensure that assemblies or assembly steps are manageable.