Can a Cleaning Scent Change How Often We Brush Away Crumbs?

Does smelling a citrus-scented cleaner make the idea of cleaning come to mind more readily? And could that association also lead people to use their hands to tidy their immediate surroundings?

A 2005 study explored these questions in three experiments. In the presence of the cleaner’s scent, participants responded more quickly to cleaning-related words and were more likely to include cleaning in their plans. In the final experiment, they also brushed away biscuit crumbs more often after leaving the scented room.

Looking beyond the idea that a pleasant scent improves mood

Holland, Hendriks, and Aarts focused on the connection between scent and meaning. If people use citrus-scented cleaners in everyday cleaning, they may associate that smell with the act of cleaning. The researchers examined whether the scent could make that knowledge more accessible and influence thoughts and actions.

The main aim was to investigate a cognitive pathway, involving what a smell brings to mind, rather than only approach or avoidance responses to its pleasantness. Questions after the experiments also checked whether participants had noticed the scent or its influence.

Experiment 1: Identifying cleaning-related words more quickly

The first experiment involved 50 Dutch university students. Randomly assigned to either a scented room or a room without scent diffusion, they decided as quickly and accurately as possible whether strings of letters on a screen were real words.

In the scented condition, a container holding all-purpose cleaner in lukewarm water was placed out of sight. Of the 40 letter strings presented, 20 were real words, including six related to concepts such as cleaning, tidying, and hygiene. The other 14 were control words, such as bicycle and desk. A preliminary study had matched the words for pleasantness.

After excluding one participant whose responses were extremely slow overall, the analysis of 49 participants showed that the scent’s effect differed between cleaning-related and control words. Responses to cleaning-related words were faster in the scented condition, whereas responses to control words were similar across conditions. The interaction between scent and word type had a p-value of .04.

This pattern fits the explanation that cleaning-related knowledge became more accessible, rather than all responses simply becoming faster.

Experiment 2: Including cleaning in plans for the day

The next experiment involved a different group of 56 university students. The scent manipulation was the same. Participants were told that the study concerned everyday activities and asked to list five things they planned to do during the rest of the day.

Two judges who did not know the condition or hypothesis checked whether those plans included cleaning or tidying. Cleaning-related activities appeared in the plans of 36% of participants in the scented condition, compared with 11% in the control condition. The difference was statistically significant.

The measure here was what participants thought of and wrote down as a plan, not how often they actually cleaned after going home. It extended the first experiment’s finding about easier word processing to the possibility that cleaning becomes more likely to enter thoughts about what to do next.

Experiment 3: More movements to remove crumbs?

The final experiment involved 22 university students, randomly assigned to scented or unscented conditions. They first completed a questionnaire in their respective rooms, then moved to another room where no scent was diffused. There, they ate a round biscuit that readily shed crumbs.

The researchers recorded their hand movements with a hidden camera while they ate. Two judges, unaware of the conditions and hypothesis, counted how often participants removed crumbs from the table.

The mean was 3.54 movements among participants who had previously been in the cleaner-scented room, compared with 1.09 in the control condition (p = .02). The distinctive point is that the difference appeared in small actions after moving to another room, rather than in cleaning a table that smelled of the same cleaner.

These numbers represent counts of crumb-removal movements. They should be distinguished from measurements of how dirty the table was or how clean it ultimately became.

How was lack of awareness checked?

After each experiment, participants were asked a series of increasingly specific questions about what they thought the study was investigating, whether they had noticed any particular smell, and whether they thought it had influenced their task performance.

Six participants in the first experiment and one in the final experiment had noticed the scent. According to the authors, however, none had identified the hypothesis that it influenced the task. They reported that excluding participants who noticed the scent did not change the overall pattern of results.

It is therefore appropriate to read the paper’s term “nonconscious” particularly as meaning that participants did not recognize the scent’s influence on their thoughts or behavior. The study did not measure everyone’s olfactory threshold and administer only stimuli below that threshold. Awareness was also assessed through participants’ own answers after the experiment.

What the three findings suggest, and what remains open

The three experiments examined the scent–cleaning connection through different measures: processing cleaning-related words, the content of plans, and actual small movements. The authors interpreted the results as suggesting that the cleaner’s smell made the concept of cleaning more accessible and connected it to an action available in the situation.

However, the experiments involved separate groups of participants. They did not directly measure a complete pathway in the same individuals in which faster responses to words caused an increase in crumb-removal movements.

The comparison was also between a particular citrus-scented cleaner and an unscented condition. There was no comparison with another pleasant scent or one less associated with cleaning. These experiments cannot establish which cleaner ingredients matter, how much pleasantness contributes, or whether the results would be the same in other cultural settings. The behavioral experiment was particularly small, with 22 participants, so broader generalization needs further testing.

Summary

In this study, participants exposed to a citrus-scented cleaner responded faster to cleaning-related words and were more likely to include cleaning in their plans for the day. In a separate experiment, participants removed biscuit crumbs more often than controls even after moving to an unscented room.

Besides feeling pleasant or unpleasant, a scent may evoke meanings associated with everyday life and influence thoughts and actions in the immediate situation. Using the familiar smell of a cleaner, this study examined that cognitive pathway in three steps.

This research was supported by the Netherlands Organization for Scientific Research (NWO).

Reference

Holland RW, Hendriks M, Aarts H. Smells Like Clean Spirit: Nonconscious Effects of Scent on Cognition and Behavior. Psychological Science. 2005;16(9):689–693. doi:10.1111/j.1467-9280.2005.01597.x.