Overloaded and at Work: Investigating the Effect of Cognitive Workload on Assembly Task Performance.

Objective: This study investigates the effect of cognitive overload on assembly task performance and muscle activity.

Background: Understanding an operator's cognitive workload is an important component in assessing human-machine interaction. However, little evidence is available on the effect that cognitive overload has on task performance and muscle activity when completing manufacturing tasks.

Method: Twenty-two volunteers completed an assembly task while performing a secondary cognitive task with increasing levels of demand (-back). Performance in the assembly task (completion times, accuracy), muscle activity recorded as integrated electromyography (EMG), and self-reported workload were measured.

Results: Results show that the increasing cognitive demand imposed by the -back task resulted in impaired assembly task performance, overall greater muscle activity, and higher self-reported workload.Relative to the control condition, performing the 2-back task resulted in longer assembly task completion times (+10 s on average) and greater integrated EMG for flexor carpi ulnaris, triceps brachii, biceps brachii, anterior deltoid, and pectoralis major.

Conclusion: This study demonstrates that working under high cognitive load not only results in greater muscle activity, but also affects assembly task completion times, which may have a direct effect on manufacturing cycle times.

Application: Results are applicable to the assessment of the effects of high cognitive workload in manufacturing.