MALE Harris sparrows are pugnacious beasts. They signal their status by the darkness of their plumage, and woe-betide any male whose signal is false—for if an itinerant ethologist blackens a subordinate’s feathers, the dominant birds recognise it as a fraud and beat it up. Normally, though, behaviour and outward appearance are in alignment, having been arranged that way by evolution, and subordinate birds do not push their luck. For female Harris sparrows, however, plumage does not matter in this way. And a paper just published in Psychological Science, by Michael Petersen of the University of Aarhus in Denmark and Daniel Sznycer of the University of California, Santa Barbara, suggests that in both respects people are similar to these birds.

Dr Petersen and Dr Sznycer were investigating the idea that a person’s political opinions might be aligned with his physical characteristics. The opinion in question was whether resources should be redistributed from the rich to the poor. The physical characteristic was strength.

Poor people might be expected to favour redistribution, and the rich to be against it, regardless of how strong they were. And for women, Dr Petersen and Dr Sznycer found that this was indeed the case. For men, though, opinion did depend on strength.

The two researchers came to this conclusion after looking at 486 Americans, 223 Argentinians and 793 Danes. They collected data on their volunteers’ strength by measuring the circumference of the flexed biceps of an individual’s dominant arm. (Previous work has shown that this is an accurate proxy for strength.) They then measured people’s status with questionnaires about their economic situation. And they determined a person’s support for redistribution by asking the degree to which he or she agreed with statements like: “The wealthy should give more money to those who are worse off”; and “It is not fair that people have to pay taxes to fund welfare programmes.” They also asked about participants’ political ideologies.

Dr Petersen and Dr Sznycer found that, regardless of country of origin or apparent ideology, strong men argued for their self interest: the poor for redistribution, the rich against it. No surprises there. Weaklings, however, were far less inclined to make the case that self-interest suggested they would. Among women, by contrast, strength had no correlation with opinion. Rich women wanted to stay rich; poor women to become so.

The researchers’ conclusion, then, is that if, like a subordinate Harris sparrow, you are not in a position to fight your corner, it makes sense not to provoke trouble. In the distant past, when such instincts would have evolved, doing so would have been dangerous, and possibly fatal.

Women, by contrast, rarely fight physically for resources in the way that men do, so their psychologies do not need to be aligned with their physical prowess. The hunt for female physical and political correlates will therefore have to search for more subtle signals.