According to the study, conducted by researchers at the Kinsey Institute for Research in Sex, Gender, and Reproduction at Indiana University, men report a variety of different experiences involving sexual desire and arousal.

Men participating in focus groups expressed a range of experiences and feelings relating to such matters as the relationship between erections and desire, the importance of scent and relationships, and a woman's intelligence.

"We have a lot of assumptions about how men think and feel and behave sexually," said Erick Janssen, associate scientist at the Kinsey Institute.

"We use all kinds of methods to measure men's sexual responses; in addition, we use questionnaires and surveys to ask about sexual behaviours. It's less common to sit down with men and ask them to talk about their experiences," Janssen said.

In the study, the focus groups involved 50 men divided into three groups based on their age (18-24 years, 25-45 years and 46 and older).

Different experiences were reported by different men -- factors like depression or a risk of being caught having sex were reported by some as inhibiting sex, while others found that they can enhance their desire and arousal.

An erection is not the main cue for men to know they are sexually aroused. Most of the men responded that they can experience erections without feeling aroused or interested, leading researchers to suggest that erections are not good criteria for determining sexual arousal in men.

Many men found it difficult to distinguish between sexual desire and sexual arousal, a distinction prominent in most sexual response models used by researchers and clinicians.

The changes in the quality of older men's erections had a direct effect on their sexual encounters, including, for some, a shifting focus to the partner and her sexual enjoyment. Older men also consistently mentioned that as they aged, they became more careful and particular in choosing sexual partners.

The sexual history of women also mattered to the men, but differently for different age groups. Sexually experienced women were considered more threatening by younger men, who had concerns about "measuring up", but such women were considered more arousing for older men.

The findings of the study ultimately could lead to a more effective questionnaire for the dual control model but also can inform research efforts to better understand the variability in sexual behaviour.

"One of the main conclusions of the focus group study is that, just like women, men are different," Janssen said.

"Sex researchers tend to focus a lot on differences between men and women, while not giving as much attention to the differences that exist among men and women. This research is part of a larger agenda at the Kinsey Institute, of looking at individual differences. This dates back to Alfred Kinsey's original research, but in our current research we not only try to capture the variations in men and women's sexual experiences -- we also try to understand better what explains variations in those experiences," Janssen added.

The study is published in the journal Archives of Sexual Behaviour.