TRY as they might, scientists have been unable to find compelling evidence to support the ''Napoleon complex'', the popular idea that shorter men are more aggressive than taller counterparts.
But new research suggests the complex may at least apply to certain types of fish and other members of the animal kingdom.
Within a species, the scientists say, smaller males are sometimes more aggressive and prone to launching attacks against would-be intruders - despite the likelihood of losing in an all-out fight.
Conflict between males of the same species is common among animals, says Monash University evolutionary biologist Bob Wong. ''But questions remain as to when, how and by whom aggression should be initiated,'' he says.
Working with researchers in Sweden and Finland, Dr Wong studied aggression in the desert goby (Chlamydogobius eremius), a small, colourful species of Australian freshwater fish found in waterholes, spring-fed pools and desert streams west of Lake Eyre in South Australia.
Males perform elaborate courtship displays to attract females, and any eggs become his responsibility. If an intruder approaches, the male will often launch what might be regarded as a pre-emptive strike.
The aggression typically occurs in distinctive ''bouts''. These involve the resident male darting out from the eggs, repeatedly attacking the intruding male and then returning to the nest.
''If males are allowed to interact physically, aggression can escalate to combat situations, with the fish locking jaws and grappling with their opponent,'' Dr Wong says. ''In such fights, the winner will typically be the larger male.''
The scientists scrutinised the behaviour of aquarium gobies. The nest's perceived value was manipulated by exposing half of the residents to sexually receptive females for two days before the trial - and then exposing the nest holders to a male intruder.
Male aggression was unaffected by perceived mating opportunities, Dr Wong says. It was also unaffected by an intruder's size. ''Instead, aggression was negatively related to the size of resident males. In particular, smaller gobies attacked sooner, and with greater ferocity, than larger ones.''
If an intruder is more likely to flee than retaliate, small males may benefit from launching an attack because this helps them avoid revealing their inferiority to the intruder.
Aggressive male gobies were said to display the ''Napoleon complex'' - named after the French emperor Napoleon Bonaparte, believed to have compensated for his allegedly short stature with an aggressive personality.
Previous studies have shown little support for the Napoleon complex in humans, but studies on other species also suggest that the so-called Napoleon complex might be a common phenomenon in the animal world.