The effect of worker learning and forgetting on storage reassignment decisions in order picking systems

• Order picking involves a high amount of manual human work and is a very labor- and time-consuming task.
• The impact of learning and forgetting in order picking and its implications on storage assignment decisions is studied.
• Learning and forgetting is integrated in an analytical order picking time model and tested in a numerical study.
• The results show that learning and forgetting should be considered in order picking to achieve a proper planning.
• More research is needed to study the effects of human factors in order picking.

Order picking is a time-intensive and costly logistics activity as it involves a high amount of manual work. Prior research has mostly neglected the influence of human factors on the efficiency of order picking systems. This paper develops a mathematical model that investigates the impact of learning and forgetting of a heterogeneous workforce on order picking time and, consequently, on storage assignment decisions. In particular, the paper investigates when to change a storage assignment and when to keep it if learning and forgetting occur among the members of an order picking workforce. The results show that learning and forgetting should be considered in order to achieve a proper planning of storage assignment strategies.