A study by Australian and Chinese researchers has found that our circadian rhythms significantly influence what we choose to buy, with hedonic purchases—items that are luxurious, indulgent, or decadent—spiking sharply in the early evening. According to the research published in the Journal of Retailing and Consumer Services, the number of such purchases rises dramatically at 7pm and peaks at 8pm. In a controlled experiment, 200 participants asked to choose between chocolate lava cake and fruit at 8pm were 60% more likely to opt for the cake than those asked at 10am.

The 8pm spike across nearly 250,000 transactions

The researchers analyzed the timing and content of nearly 250,000 online shopping transactions to map how hedonic purchases fluctuated with the hour. The data showed a clear pattern: indulgence-seeking behavior remained low through the morning and afternoon , then surged in the early evening, with the peak occurring at 8pm. This finding, reported in the Journal of Retailing and Consumer Services, suggests that our internal body clocks create a window of vulnerability to tempting offers. The study's authors noted that the increase was not merely a function of being awake longer,but a systematic daily rhythm.

Chocolate lava cake vs. fruit: the 60% swing

To test the mechanism behind the transaction data, the team conducted a second experiment in which 200 people were asked to imagine they were doing their daily shopping and wanted to treat themselves—either to a chocolate lava cake or a bowl of fruit. Crucially, one group received the question at 8pm and another at 10am. The evening group was 60% more likely to choose the indulgent cake, according to the study. The researchers controlled for fatigue , measuring psychological arousal instead, and found that participants were more aroused in the evening,which they argue provided the motivational resources to justify a pleasure-oriented choice.

Why psychological arousal, not fatigue, is the driver

The conventional wisdom might attribute evening indulgence to willpower depletion after a long day, but the study directly challenges that idea. Writing in the Journal of Retailing and Consumer Services, the scientists state: 'The heightened preference for hedonic options in the evening is not driven by fatigue, but rather by the natural rise in psychological arousal which provides the motivation resources necessary to pursue and justify pleasure-oriented choices.' Hedonic consumption, they explain, requires overcoming the 'guilt' of indulgence, and the high-arousal state of the evening equips consumers to navigate that hurdle. This suggests that our body clocks prime us for reward-seeking at a specific time of day.

What the study leaves unclear about your 8pm treat

While the findings are robust for online shopping and a single dessert scenario, several questions remain unanswered. The transaction data reflects only digital purchases, not in-store behavior, where external cues like packaging and placement may also play a role. Additionally, the experiment tested only one pair of options (cake vs. fruit); it is unknown whether the effect holds for other hedonic categories, such as salty snacks or luxury goods. The study also does not address individual variations in circadian timing—some people are night owls, others morning larks—which could shift the peak indulgence window. finally, the research was conducted on an Australian and Chinese population, leaving cross-cultural differences unexplored.