Wake up and smell the coffee: sense of smell is far worse when busy, research finds 

coffee
The research checked whether participants could smell the coffee  Credit: PA 

People have a far worse sense of smell when they are busy, research suggests.

A study found that those whose attention is focussed on tasks are far less likely to notice odours - even those which might otherwise tempt them.

Researchers from the University of Oxford and the University of Sussex tested the theory of “inattentional smell blindness” on a group of 40 people.

Half were given a complex task on computer screens, with the remainder given simple duties, in a room in which coffee beans had been hidden.  

Afterwards they were asked to describe the room, with follow-up questions to detect if they had noticed the odour.

Those who were trying to engage with the more demanding process were 43 per cent less likely to notice the aroma in the room, the study found.

The scientists said the study proved that sense of smell diminished when participants were distracted - echoing the common advice to “wake up and smell the coffee”.

It might mean dieters would do best to keep busy, finding themselves less tempted by food smells, they suggested.

But they said further research would look at whether the same held true in situations of danger - meaning overworked engineers might be less likely to smell a gas leak, or drivers might miss warning signs on busy motorways.

Researchers said the findings about smell were particularly significant, because it is already known that people become less sensitive to smell once they are used to it, giving them a limited window of time to act.

Researcher Dr Sophie Forster, from Sussex University, who carried out the study with Prof Charles Spence, from Oxford  University, said: “If you are busy focusing on a task you may be less likely to be tempted by food smells.

“Our test was done with the smell of coffee but the next step for us will be to test ‘threat smells’ such as smoke and gas. Could it be, for example, that drivers who are concentrating on a busy motorway and perhaps are also engaged in a conversation, might may fail to notice a burning smell which should act as a warning sign? Or perhaps the same is true of engineers who work busily in situations which place them at risk of a gas leak.”

The study also confirmed the theory of habituation - that people have a short window of around 20 minutes to notice smells, after which the chance is much diminished.

The researchers were testing the “perceptual load hypothesis”, which is an idea that people can only perceive sensory information until their capacity is full.  

It explains the well-known ‘Did you see the gorilla?’ inattentional blindness study, where observers are asked to focus on the number of ball passes between players wearing white.

The vast majority of those who try the test fail to notice a person in a gorilla suit who walks across the scene and performs a dance.

Dr Forster said: “In the case of visual or auditory information, we tend to notice it once we are no longer busy. However, the brain can habituate to smells so strongly that they cannot be detected even when we are specifically asked about smells in the room. If this habituation occurs during the period that people are distracted by a task, the opportunity to detect a smell may be missed.”

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