Next, the team observed that some neurons respond differently to two very dissimilar odors, but the same to similar smells. The researchers called these neurons reliable cells. This small group of cells helps flies quickly distinguish between differing odors. Another much larger group of neurons responds unpredictably when exposed to similar smells. These neurons, which the researchers call unreliable cells, might help us learn to identify specific scents in a glass of wine, for example.

“The model we developed shows these unreliable cells are useful,” Srinivasan says. “But it requires many learning bouts to take advantage of them.”

— Read more in Smells like learning at EurekAlert.

For the new experiment, 28 participants each entered the smellscape four times. The placement of eight "odor objects" in the environment—smells like orange or banana—always stayed the same. What changed was where participants were placed in the virtual reality arena and which target odor they needed to find.

The results surprised and excited the researchers. "Although the human sense of smell has been poorly regarded across the five different senses, we are now able to establish that human subjects can actually navigate spaces using their nose in the context of a particular type of virtual reality environment," Gottfried says.

— Read more in How humans use their sense of smell to find their way at Medical Xpress.

They also sat in front of a screen filled with a random color, whilst an ultrasonic diffuser pumped one of six odors into the room – caramel, cherry, coffee, lemon, peppermint, or water as a control – for five minutes. Using two sliders, participants were then asked to manually adjust the color on the screen to what they perceived to be true neutral gray.

The study found that people had a weak but significant tendency to shift the color too far away from neutral gray, in different but predictable ways depending on the scent – except for peppermint. The smell of coffee made participants perceive gray as a more red-brown color, whilst caramel led to more of a yellow-brown. To be expected given their respective dullness, odorless water corresponded to true neutral gray.

– Read more in Our Sense Of Smell Changes How We See Color at IFLScience.