We can identify more than One trillion Smells: Study

Human beings have the ability to recognize more than one trillion smells, according to a recent study.

Our ability to perceive millions of colors and distinguish half million different sounds is proved in researches. While studies that suggested humans can identify up to 10,000 different smells were accepted in the past they did not confirm the exact number.

Scientists from the Rockfeller University's Laboratory of Neurogenetics and Behavior tested volunteers' capacity and sensitivity to detect smells from complex mixtures of scents. Noting the extent of brain and nose sensitivity to the mixed odors, they found that human beings can identify about one trillion smells.

According to the experts, human beings are unaware of their smell-distinction ability in everyday life and pay very limited attention to it. Odor emitting substances have complex mixes of molecules with varying levels of smell of which only the dominant odors can be perceived. This aspect of odor differentiation makes it more complicated to study unlike vision and hearing.

 Andreas Keller, study author and researcher at the Rockfeller University's Laboratory of Neuro-genetics and Behavior said in a press release, "The message here is that we have more sensitivity in our sense of smell than for which we give ourselves credit. We just don't pay attention to it and don't use it in everyday life,"

For the trial they created mixtures using 128 odor molecules responsible for emitting scents and fragrances like orange, anise and spearmint that were mixed in varying proportions. They made mixtures composing 10, 20 and 30 concentrations of fragrant elements. The participants were give three containers of these mixtures of which two were similar smelling and asked to pick an odor that was different.

Keller said, "Our trick is we use mixtures of odor molecules, and we use the percentage of overlap between two mixtures to measure the sensitivity of a person's sense of smell."

 It was found that subjects could differentiate the odors in mixtures that contained almost 51 percent of the same components. When the proportion of components mixture was higher than 50 percent, very few participants could detect the change.

Marcelo O. Mag nasco, co-author and the head of the Laboratory of Mathematical Physics at Rockefeller  said, "It turns out that the resolution of the olfactory system is not extraordinary - you need to change a fair fraction of the components before the change can be reliably detected by more than 50 percent of the subjects. However, because the number of combinations is quite literally astronomical, even after accounting for this limitation the total number of distinguishable odor combinations is quite large."

The authors believe many more mixture and combinations of the odors can be created and the estimated one trillion odors are too less compared to human beings' competency to gauge odor differences. Unlike our ancestors who made extensive use of this sensory function, we have limited smelling abilities due to lifestyle habits like bathing and use of electronic items like refrigerators.

More information is available in the journal Science.