Mice are valuable in research because they're genetically similar to humans and, unlike in people, scientists can manipulate their genes to better understand brain functions, psychology and psychiatry. However, there is a drawback.

Human research in psychology and psychiatry traditionally relies on questionnaires and self-reporting by study subjects. And let's face facts: It's hard to get a mouse to hold a pen, let alone fill out a form.

But now, Japanese researchers, as reported in the journal PLoS One, have come up with a new holistic approach to assessing animal model behavior: Observe the mouse's lifestyle. Every move of the rodent is recorded, utilizing pressure sensors under the cage, and the information is collected for more than 24 hours.

So what happens when mice stop being polite ... and start getting real? Scientists processed the recorded information to chronicle the mouse's movements, and their durations; this provided a mathematical representation of the probability of the mouse's small or large actions. The researchers then monitored humans' wrist activity for more than 24 hours, and were surprised to discover no difference in behavior statistics between mice and men.

The team also found that mice with an artificially eliminated gene regulating the circadian rhythm evinced similarities with humans suffering from major depressive disorder, a finding that could help in the diagnosis, evaluation, and treatment of the "depression genome."

The observation that healthy mice show behavior patterns during rest and activity indistinguishable from humans may also have a significant impact on investigations into higher brain functions.