It is a safe bet that few women ever wanted to mother Clint Eastwood.

The steely, narrowed eyes. The rugged jawline. The thin-lipped sneer. This is the face of a man to save the homestead from marauding Indians, to stare down an outlaw in a saloon. But not to cuddle.

Now, take Paul McCartney -- he of the doe eyes, chipmunk cheeks and teddy bear chin. Ten thousand teeny-boppers can't be wrong. The man is adorable.

The faces of Eastwood and McCartney represent the two extremes in male facial types, each of which, psychologists argue, elicits its own distinctive emotional reactions.

People with facial features characteristic of infants bring out the same feelings of nurturing and compassion that babies do. Men with mature, masculine features, on the other hand, convey vigor and sexual power.

This much is conventional wisdom. But writing in the latest issue of the Journal of Personality and Social Psychology, three researchers led by University of Louisville psychologist Michael Cunningham argue that the differences in male facial types may also serve to explain that oldest of questions: Why are women attracted to men?

Citing recent behavioral experiments, the researchers present a controversial theory they call the multiple motive hypothesis. It says that women are most attracted to male faces that combine the best elements of both these extremes -- the large eyes and medium-to-small nose of the baby's face with the strong jaw and wide cheekbones of the mature man's face.

Women prefer men, in other words, whose faces inspire both their inclination to nurture and their desire for a sexually mature partner.

They want men they can cuddle like McCartney and cling to like Eastwood. They like Robert Redford (big eyes and strong jaw) over Michael Jackson (no chin). They like Mel Gibson (a god) over Al Pacino (nose much, much too big). O.J. Simpson and Tom Selleck also qualify as perfect scores, according to the researchers.

This theory is not about true love, of course. Why one woman or man becomes truly committed to another results from a host of factors of which facial attractiveness is only one. Nor is it about body shape, which obviously plays its own significant role. This is about impressions formed by photographs, by chance encounters, by staring deep into a man's eyes. This is about faces that trigger that first quickening of the pulse, that first hint of longing, that weakening of the knees. This is about Wow! Universal Facial Preferences

The implications of the theory are enormous. The researchers claim that these standards of attractiveness cut across social, racial and cultural lines, that while women around the world have different tastes in male weight, body type and grooming, everywhere they like the same thing in a man's face.

Moreover, the psychologists maintain that their experimental results allow them to quantify the components of male attractiveness. They can predict, down to the hundredth of a millimeter, what the most attractive eye size is, what turns a chin from a liability into an asset and how big a nose a man can carry before women start to look away.

Are we close to knowing what the perfect male face looks like?

"This is an interesting theory with an interesting underlying hypothesis," said Brandeis University psychologist Leslie Zebrowitz, who works in the same field. "But it's controversial. . . . There may be some universal {principles} of attractiveness. But I'm not so convinced that we know yet what they are."

The idea that faces fall into types and that those types can in turn inspire strong emotions is not a new one in behavioral psychology. Zebrowitz, for example, has used the same baby-face/mature-face distinction in research on social attitudes.

"Baby-faced {people} are seen as more naive, more submissive, warmer, more honest and physically weaker than their age mates," she says. Mature-faced men, by contrast, are perceived as being stronger, shrewder and more dominant.

In a long study of courtroom trials, Zebrowitz found that the more baby-faced the defendant looked, the more likely he was to be acquitted of crimes involving intentional misconduct. However, in keeping with the image of baby-faced naivete and weakness, defendants of that type were more likely to be found guilty when charged with negligent behavior. For mature-faced types, the exact reverse was true. Dimensions of the Draw

Cunningham's research tries to determine how these emotional reactions to facial features fit into a man's attractiveness to women. To do this, he and his colleagues gathered head-and-shoulders photographs of young men and showed them to large groups of mainly white, college-age women, asking them to rank the pictures using a variety of attractiveness scales. Then the researchers broke down the faces into 25 categories, painstakingly measuring the dimensions of each feature to determine which part of the face correlated best with high attractiveness scores.

The results -- which were substantially the same for both the white women and later studies with groups of Hispanic, Asian and black women -- found larger-than-average eyes to be the most important factor.

"Eyes convey information," Cunningham says. Big, babylike eyes suggest spontaneity, innocence, vulnerability. Small eyes, through a mark of maturity, may "convey a lower need for affection and care."

On the other hand, women didn't seem to like an underdeveloped, baby-like jaw and chin. "Jaws convey age, but also strength," he says, "It signals that a man has gone through puberty."

Wide cheeks and high cheekbones -- signals of male physical maturity and strength -- also are good. But so are smiles, which have nothing to do with sexual maturity and are a universal signal of joy, responsiveness and sociability.

High-status clothing -- dark suits with a tie -- seem to help, as does shorter hair, both of which could be interpreted as symbols of achievement.

"A man who possesses an attractive combination of {infant-like}, mature, expressive, and good grooming features; who looks outgoing and well dressed, rugged but also cuddly, and masculine but not extremely sex-typed, may appear to offer the best chance for an affectionate, high-status . . . mate," the study concludes.

What women want, Cunningham says, is a face that has it all.

According to surveys of female college undergraduates, the ideal man -- at least in facial type -- combines two contradictory sets of features. These are babylike traits (big eyes, chubby cheeks) and those that bespeak maturity and power (prominent cheekbones, a large chin). The theory is that the combination appeals simultaneously to a woman's desire to nurture and to seek a powerful, sexually mature mate.

According to the researchers, two men whose faces exemplify the ideal are actor Tom Selleck and sports announcer O.J. Simpson. Men whose faces represent the extremes would include singer Paul McCartney (big eyes and, at least in his Beatle days, fat cheeks but a small chin) and actor Clint Eastwood (strong chin and cheekbones but squinty eyes).

The researchers came to their conclusions after asking hundreds of women to evaluate photos of men. Nineteen facial features (on diagram) were measured to arrive at numerical scores that could be correlated with the preferences.