Does Sense of Smell affect Sense of Time?

Imagine you are walking in a park, which has lots of roses and the air is filled with aroma. You move softly and start taking deep breaths just to appreciate more of rose aroma. You feel nice and relaxed … but wait, what happened to your sense of time. Did you notice that your subjective time is not in sync with the physical time? Or take another example when you are walking and you happen to encounter a bad or intolerant odor, again you experience altered sense of time. Though these incidents are common, time researchers have rarely addressed this question- “Does sense of smell affects sense of time?”

A recent study published in Frontiers in Psychology (2016), by Jean-Louis MILLOT [Université de Franche-Comté, France] and his collaborators have tried to shine some light on the odor and time perception relationship. They used decanoic acid (capric acid), which is a saturated fatty acid having an unpleasant goat like odor, as their stimulant. This odorant was used, as they wanted to study the effect of aversive or negative odor on time perception. Subjects were asked to wear a mask soaked in 1ml pure decanoic acid for odor condition and 1ml diethylphtalate, an odorless diluent, for control or without odor condition.

Temporal bisection task was used to measure time perception of auditory stimuli (white noise) in the presence or absence of odorant. This study was performed with two groups (N=36 each), for one group the time range was in sub-second (centered around 400ms) and for other group it was in supra-second (centered around 2000ms). Two time ranges were used to investigate whether odor influences time perception in a multiplicative manner (i.e. by increasing the pacemaker speed). The logic is if any factor influence pacemaker speed then the effect should change as the function of actual duration.

After the initial standard duration training, the experiment consisted of two test blocks. In each group, half of the participants performed the training and first test block without odorant and second test block with odorant. On the other hand, remaining half of the participants performed the training and first test block with odorant and second test block without odorant.

Results showed that irrespective of whether the odorant was used in either first or second test block, participants underestimated the auditory stimulus in the presence of odorant compared to without odorant condition for sub-second time range whereas participants overestimated the auditory stimulus in the presence of odorant compared to without odorant condition for supra-second time range.

They used attention gate model to explain their findings for sub-second time range. In attentional gate model, it is assumed that the attention governs the gate of the internal clock, such that if more attention is allotted to temporal processing then the gate remains closed for longer time leading to more pulses getting accumulated in the accumulator. If some stimulus grabs more attention (non-temporal processing) then the amount of attention left for temporal processing reduces and hence will lead to lesser number of pulses being accumulated in the accumulator. In the sub-second range the attention was diverted away from time to the odor, which led to the accumulation of lesser number of pulses in the accumulator compared to the without odor condition.

But the story is more complicated as opposite effect of odor was seen for supra-second range. They explain this result by suggesting that unpleasant odor induce negative emotion and increase arousal. And such increase in arousal increases the pacemaker speed, leading to temporal expansion.

The current study may not answer all the questions about how odor influences time perception, but it definitely gives some initial inputs for researchers who wish to further investigate the unexplored territory of Odor affecting Time. For those who are interested in this topic these are some additional work on odor and time perception [Brand et al. (2016), Giovannelli et al. (2015), Schreuder et al. (2014), and Yue et al. (2016)].

References:
Brand, G., Thiabaud, F., & Dray, N. (2016). Influence of Ambient Odors on Time Perception in a Retrospective Paradigm. Perceptual and motor skills, DOI: 10.1177/0031512516647716
Giovannelli, F., Giganti, F., Saviozzi, A., Rebai, M., Marzi, T., Righi, S., … & Viggiano, M. P. (2015). Gender Differences in Time Perception During Olfactory Stimulation. Journal of Sensory Studies. doi:10.1111/joss.12191
Schreuder E, Hoeksma MR, Smeets MA and Semin GR (2014) The effects of odour and body posture on perceived duration. Front. Neurorobot. 8:6. doi:10.3389/fnbot.2014.00006
Yue, Z., Gao, T., Chen, L., & Wu, J. (2016). Odors Bias Time Perception in Visual and Auditory Modalities. Frontiers in Psychology, 7, 535. http://doi.org/10.3389/fpsyg.2016.00535

Source article:
Millot, J.-L., Laurent, L., & Casini, L. (2016). The Influence of Odors on Time Perception. Frontiers in Psychology, 7, 181. http://doi.org/10.3389/fpsyg.2016.00181

— Mukesh Makwana,
Doctoral Student,
Centre of Behavioural and Cognitive Science,
University of Allahabad, India.