THAT some people make weird associations between the senses has been acknowledged for over a century. The condition has even been given a name: synaesthesia. Odd as it may seem to those not so gifted, synaesthetes insist that spoken sounds and the symbols which represent them give rise to specific colours or that individual musical notes have their own hues.

Yet there may be a little of this cross-modal association in everyone. Most people agree that loud sounds are “brighter” than soft ones. Likewise, low-pitched sounds are reminiscent of large objects and high-pitched ones evoke smallness. Anne-Sylvie Crisinel and Charles Spence of Oxford University think something similar is true between sound and smell.

Ms Crisinel and Dr Spence wanted to know whether an odour sniffed from a bottle could be linked to a specific pitch, and even a specific instrument. To find out, they asked 30 people to inhale 20 smells—ranging from apple to violet and wood smoke—which came from a teaching kit for wine-tasting. After giving each sample a good sniff, volunteers had to click their way through 52 sounds of varying pitches, played by piano, woodwind, string or brass, and identify which best matched the smell. The results of this study, to be published later this month in Chemical Senses, are intriguing.

The researchers' first finding was that the volunteers did not think their request utterly ridiculous. It rather made sense, they told them afterwards. The second was that there was significant agreement between volunteers. Sweet and sour smells were rated as higher-pitched, smoky and woody ones as lower-pitched. Blackberry and raspberry were very piano. Vanilla had elements of both piano and woodwind. Musk was strongly brass.

It is not immediately clear why people employ their musical senses in this way to help their assessment of a smell. But gone are the days when science assumed each sense worked in isolation. People live, say Dr Spence and Ms Crisinel, in a multisensory world and their brains tirelessly combine information from all sources to make sense, as it were, of what is going on around them. Nor is this response restricted to humans. Studies of the brains of mice show that regions involved in olfaction also react to sound.

Taste, too, seems linked to hearing. Ms Crisinel and Dr Spence have previously established that sweet and sour tastes, like smells, are linked to high pitch, while bitter tastes bring lower pitches to mind. Now they have gone further. In a study that will be published later this year they and their colleagues show how altering the pitch and instruments used in background music can alter the way food tastes.

In this experiment, each volunteer was given four pieces of toffee. While they were eating two of them, a sombre, low-pitched piece of music played on brass instruments filled the air. They consumed the other two, however, to the accompaniment of a higher-pitched piano piece. Volunteers rated the toffee eaten during low-pitched music as more bitter than that consumed during the high-pitched rendition. The toffee was, of course, identical. It was the sound that tasted different.