Blinking Stimulus May Increase Attention Alertness in Warehouse Workers

Warehouse Employees in Distribution Warehouse
Two coworkers checking warehouse worker lifting a pallet of good.
Researchers compared the effectiveness of different light colors and light types on attention alertness.

This article is part of Optometry Advisor’s conference coverage from the 2021 meeting of the American Academy of Optometry, held in Boston from November 3 to 6, 2021. The team at Optometry Advisor will be reporting on a variety of the research presented by the primary eye care experts at the AAO. Check back for more from the AAO Optometry 2021 Meeting..

Warehouse work is becoming increasingly common among the American workforce. The industry expanded its workforce by approximately 37% between 2014 and 2017, according to the US Bureau of Labor Statistics. The same report shows it is expected to continue growing, perhaps by more than 20% between 2016 and 2026 — due, in large part, to the popularity of online retail.1

Researchers at the American Academy of Optometry 2021 meeting in Boston presented data relevant to the safety of this growing sector. They sought to develop a blinking stimulus to provide warehouse workers a better visual signal to increase alertness of lift truck and other heavy machinery traffic. The Pacific University-based research team explained that workers on foot being struck by forklifts and other vehicles are common warehouse accidents.2

“While various safety devices such as alarms and zone warning lights have been added to reduce lift truck accidents, their effectiveness is diminished by the loud echoing and chaotic ambient reflections inside the warehouse,” investigators explained.

The study included 36 adults with 20/40+ vision. Investigators compared the effectiveness of different light colors (red, green, blue) and light type (constant vs blink) on attention alertness. Participants viewed videos of a lift truck traveling in a warehouse while standing at the viewing spot where the camera performed video recording. When the lift truck traveled in 1 of 3 aisles, different combinations of light color and type reflected off the ground to warn the truck is approaching. When the truck appeared, participants were asked to press a button immediately.

All premature responses were voided. Participants were told to have fast and accurate responses while focusing on the task (single task) or performing a 2-back memory task (dual task). Instant audio feedback indicated their accuracy in the dual task. Trials with no truck or no light were included as a control to lower anticipated reactions.

The researchers found that accuracy in lift truck detection was slightly reduced (94.65 vs 99.5%) with red light (P <.001). Reaction time (RT) was 0.2 seconds faster with single task vs dual task (3.9 vs 3.7 seconds) and about 0.2 seconds slower for the oldest group vs the others, according to the report. 

During all conditions, blink rate was 0.3 seconds faster compared with constant light (single: 0.36 vs. 0.39; dual: 0.38 vs 0.41). A significant interaction of light color and type was observed for red light (0.35 vs 0.43) and green light (0.38 vs 0.40), but no difference for blue light was seen (0.40 vs 0.40).  

“While red light may be less stimulating, it elicits faster responses,” the researchers said. “Further investigation on stable visible light simulation is needed.” 

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1. US Bureau of Labor Statistics. Employment projections. United States Department of Labor. Accessed November 8, 2021. 

2. Tai YC, Hayes J, Citek K. Light and attention. Poster presented at: American Academy of Optometry 2021 Annual Meeting: November 5, 2021; Boston. Board #90.