As our modern world relies overwhelmingly on sight and sound to transmit information, it might not strike you quite how acute our sense of smell is. In fact we humans can outperform the most sensitive measuring instruments in detecting certain odours, and distinguish smells from strangers from those of our blood relations. Now new research suggests our natural olfactory talents may be even greater when we use modest amounts of alcohol to reduce our inhibitions.
A team led by Yaara Endevelt-Shapira tested participants on two days: on one, tests took place before and after drinking a cup of grape juice, and on the other day, before and after a drink containing a dose of alcohol (vodka). Even though the alcohol dose was based on a single measure (35ml) adjusted for the participants’ weight, differences in how people’s bodies process alcohol meant that breathalyser measures of Blood Alcohol Content (BAC) varied from as low as 0.01 to as high as 0.1 across participants.
A smell-detection experiment involved participants indicating which of three jars of oil contained a highly diluted scent. Higher BAC did not influence performance, but when a dose of alcohol produced a low BAC (below .06), participants were able to identify more highly diluted scents than they could on their no-booze day.
In a second experiment, participants sniffed three scents and tried to tell which one differed from the other (identical) two. High BAC made this discrimination task harder, but again, low BAC had a facilitative effect, making it easier to determine the odd smell out. This task was also replicated in a field experiment, pulling people aside at a bar to test their discrimination for trios of scratch-and-sniff stickers: those punters who had already had a drink (all had a low BAC) performed significantly better than those who had not.
Taken together the findings suggest that low alcohol doses improve smelling ability, but why does it have this effect? We can’t yet be certain, however the study offers some clues that it has to do with removing people’s inhibition.
First, smell detection was worse for candidates who scored highly on an aspect of motivation called “baseline inhibitory state”, which refers to a person’s tendency to avoid or prevent negative outcomes (it was measured with items such as “I worry about making mistakes”). Participants who were inclined to hold back in this way were poorer at detecting smells.
Second, alcohol-fuelled improvement in smell discrimination correlated with how much participants’ performance dropped on the Stroop task when under the influence. This classic task involves inhibiting the meaning of a colour word in order to complete the challenge of naming the ink colour that the word is printed in. Smell discrimination improved more for participants who displayed weaker inhibitory powers on the Stroop.
The authors explained that the prefrontal cortex has inhibitory connections to the olfactory cortex, our smell centre. And cases exist where frontal brain injury has led to near-immediate improvements in olfactory ability. This evidence signature presents a reasonable case that we are constantly suppressing a superior sense of smell, but that this inhibition can be reduced by various means…including a drop of the hard stuff.
Endevelt-Shapira, Y., Shushan, S., Roth, Y., Sobel, N. (2014). Disinhibition of olfaction: Human olfactory performance improves following low levels of alcohol Behavioural Brain Research, 272, 66-74 DOI: 10.1016/j.bbr.2014.06.024