Photo: Phil Boorman (iStock)

If you’re a restaurant owner, there’s an optimal time of day you’d want your restaurant to be visited by health department inspectors—and it’s not first thing in the morning. That’s just one of the findings from a new report by two researchers, one from Northwestern University’s Kellogg School Of Management and one from Harvard Business School. The pair set up a research project to examine how local health inspectors could do the best possible job ensuring restaurant safety, and they found that—like all of us—inspectors are human. They’re influenced in their inspections by factors they may not even realize, like time of day.

According to the researchers, who explain the results of their investigation in the Harvard Business Review, inspectors tend to issue fewer citations at each successive restaurant they visit. While the researchers note inspectors strive for diligence and fairness, “the onerous work takes a toll on their meticulousness,” and—super relatable—they’d like to wrap up their work days on time.

“When they spent more time on inspections earlier in the day, they cited fewer violations later. And, when inspections risked prolonging their work past their normal quitting times, they cited even fewer violations,” authors Maria R. Ibanez and Michael W. Toffel write in the Harvard Business Review. They attribute this not to rushing or laziness, but instead posit that inspections are difficult, detail-oriented, and straining, so an inspector is more likely to be tired at the end of the day.

Inspectors’ schedules can influence the number of citations they issue in another way. Inspectors who found a lot of violations or worsening safety conditions at an early inspection were more likely to find violations at subsequent restaurants. Ibanez and Toffel theorize that seeing many violations at one establishment encourages inspectors to be more on guard for violations at the next.

Seeing as the researchers are management experts publishing their findings in a journal called Management Science, they make some recommendations about how inspectors could better overcome these influences. Some are related to schedules: An inspector should ideally have an even number of inspections across two days, rather than one on a first day and three on a second day, to avoid fatigue. The researchers also suggest prioritizing the most crucial inspections—hospitals, nursing-home cafeterias, etc.—and conducting those earlier in the day when inspectors’ eyes are sharpest.

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The takeaway for restaurants nervous about citations is the opposite: They’d rather have that inspector visit later in the day.