Question: Why are people marrying so much later these days? How might an economist explain this?

Answer: Think in terms of "opportunity costs," or what must be sacrificed to pursue a certain path, says Robert Frank in "The Economic Naturalist." These costs have been increasing for those who choose to marry young.

As a result, marriages worldwide have been pragmatically delayed. For example, in the U.S. in 1960, the average age at first marriage was 22.8 for men, 20.3 for women; by 2004 the figures were 27.4 and 25.8 (28.7 and 26.9 in Australia).

A key reason is that the amount of education needed to get a good job has increased. But early marriage makes pursuing higher education tougher, especially for young parents. And to the extent that people nowadays hope to marry someone successful, the information required to predict this is not available as early as it used to be.

Also, early marriage traditionally seemed to promise winning an attractive partner before all the desirable ones were claimed. But with higher incomes and education levels and greater mobility has come access to a steadily growing pool of potential marriage partners. Even the benefits of having kids while young and healthy have diminished with improvements in medicine and longevity. In short, the premium on marrying young has shrunk, putting those wedding bells on hold, at least for a while.

Question: Next time you come face-to-face with an unfamiliar dog wagging its tail, could you determine whether to reach out to pet it or step back in deference?

Answer: Check the tail-wag bias, advises Michael Shermer in Scientific American magazine. If the wagging tail leans toward the dog's right, you're safe; to the dog's left, don't move.

Italian neuroscientists and veterinarians at the University of Bari tested 30 mixed-breed dogs encountering four stimuli: their owner, an unfamiliar person, a cat and an unfamiliar dominant dog. Owners elicited a strong right-wag bias, other people and the cat triggered a slight right wag, the dog a strong left. Apparently, since the left brain controls the right side of the body and vice versa, the nerve signals cross the body's midline and cause a more rightward wag when the dog's left brain is experiencing a positive emotion. Birds, fish and frogs show similar left-brain/right-brain differences in approach/avoidance behavior.

Question: Can you figure the common denominator for the following: your baby's cute face, the cinematic extraterrestrial creature E.T., Cabbage Patch dolls and the lovable cartoon character Mickey Mouse?

Answer: Probably the best answer is "neoteny," the retention of juvenile features such as large round heads relative to body size, adult-size eyes, round cheeks, a flat nose, short arms and relatively little body hair, says David Bjorklund in "Why Youth Is Not Wasted on the Young."

These types of characteristics are evolutionarily endearing to adults, whose helpless babies may keep them awake all night but are so cute it's hard not to love them anyway. Neoteny is shared by the young of many species, including dogs whose faces are deliberately bred for this to help ensure their adoption and well-being.

Retaining neotenous features longer than other species, we big-brained humans enjoy a protracted childhood that is key to learning and to the development of our complex, sophisticated culture. "Science fiction writers and UFOlogists seem to be aware of this evolutionary trend, typically describing futuristic humans and visiting space aliens as short, hairless creatures with large heads and big eyes."

Send STRANGE questions to brothers Bill and Rich at [email protected].