Why Friday Afternoon Is the Worst Time to Shop Online — Marketers Know When Your Guard Is Down

We have all been there: a package arrives at the door, and we find ourselves staring at an item we barely remember purchasing. According to Matthew Pittman, an associate professor of advertising at the University of Tennessee, we are often victims of "cognitive load" triggered by social media use at exactly the wrong time.

The Instagram Experiment

Joined by researchers Stan Li and Bixuan Sun, Pittman conducted three experiments to test how people process online ads for eco-friendly products. Half of the participants scrolled through Instagram for just 30 seconds, while the other half did not. Both groups then viewed ads for laundry detergent, phone cases, and reusable water bottles.

The findings revealed a consistent pattern. Under normal conditions, participants preferred "implicit" conclusions—ads that presented facts and let the consumer decide. However, after just 30 seconds of scrolling, the preference flipped. Those under cognitive load preferred "explicit" conclusions where the brand flatly declared itself "the best."

Confidence as a Proxy for Credibility

The study found that when the brain is tired, bold and clear claims make a brand seem more credible. Consumers don't consciously realize they are being told what to do; instead, the assertiveness of the ad feels reassuring. This is especially true for sustainability claims, which are difficult to verify physically.

When we have the mental bandwidth, we prefer to reach our own conclusions. But when our attention is split—much like trying to evaluate a recommendation while distracted by texts and other tasks—a brand that spells out the conclusion for us provides a sense of relief. The confidence of the message is mistaken for expertise because we lack the spare capacity to evaluate the evidence ourselves.

The Friday 4 P.M. Warning

The research emphasizes the importance of being in the right mental state before clicking "buy." Times of high brain fog—late afternoon, late in the week, or right before major events—are high-risk zones for poor financial decisions. Pittman specifically warns against shopping on Friday at 4 p.m.

While explicit claims can boost a brand's credibility in the short term, the researchers warn that if these claims aren't backed by evidence, they can trigger a "boomerang effect," leading to brand resentment once the consumer's head clears. The takeaway for shoppers is simple: wait until the following morning to finalize that cart.