NEW YORK (Reuters Life!) - Chocolate chip cookies baking in the oven. Fresh cut grass. Your spouse’s natural body odor. Smells can invoke memories, sexually arouse people, or even drive you mad.

A man walks under an umbrella during rain in the centre of Berlin July 4, 2007. Chocolate chip cookies baking in the oven. Fresh cut grass. Your spouse's natural body odor. Smells can invoke memories, sexually arouse people, or even drive you mad. REUTERS/Hannibal Hanschke

Psychology professor Rachel Herz from Brown University in Rhode Island has spent 17 years studying the human sense of smell, finding it is the most emotionally evocative sense and the one most closely tied to mental health and happiness.

In a new book, “The Scent of Desire,” she argues Michael Hutchence, frontman of Australian rock band INXS, may have been driven into a deep depression after losing his sense of smell in an accident which may have contributed to his 1997 suicide.

“This is a famous rock star who had everything but lost his sense of smell. This, in some people, can trigger a serious depression that gets worse over time,” Herz told Reuters ahead of the release of her book this week.

“Smells really can alter and influence our moods and behaviors. There’s no question that from a rudimentary survival basis vision is the most important sense for humans but for quality of life it is probably the most important sense.”

Herz said she was struck by the importance of smell when acting as an expert witness in a court case for a woman who lost her sense of smell after suffering severe head injuries in a car accident.

The woman, who was aged in her 20s with a good career, explained how losing her sense of smell affected everything in her life from her ability to be a homemaker, to being intimate with husband, to her paranoia about her body.

“That really hit home with me,” said Herz.

Over the years, Herz has conducted numerous surveys and tests to gauge the psychological importance of smell.

For while taste is only bitter, salty, sour, sweet and umami or savory, all flavors come from smell, so without smell you can’t taste the difference between an apple and a potato, or a glass of red wine and a cup of cold coffee.

Herz discovered you can’t smell when you are in a deep sleep which underlines the need for auditory smoke alarms.

She also discovered that people do not have an innate reaction to smell and all responses to smell are learned.

“I was once told by someone she hated the smell of roses because the first time she smelled roses was at her mother’s funeral. That has stuck with me,” she said.

When it came to gender differences, she found women had a keener nose than men on average.

A survey she conducted in 2002 of 99 men and 99 women found that women ranked how a man smells as more important than anything else in terms of their sexual attraction to him, outranking all social features except for pleasantness.

Men, however, rated how a woman’s looks as more important and as second only in importance to a women being pleasant.

“But interestingly women’s response to fragrance was equivalent to their response to men’s body odor so if a man is wearing a fragrance they like that does the trick,” she said.

“Our emotional, physical and even sexual lives are profoundly shaped by both our reactions to and interpretations of different smells.”