Strange but True: Magic number for social groups


Q: Can you propose numbers and perhaps even a sort of formula for maintaining human friendships?

A: The magic number is about 150 for the natural size of social groups, according to University of Oxford's Robin Dunbar, as reported by Catherine deLange in "New Scientist" magazine. This number is even in the right ballpark for modern online groups. "Facebook allows up to 5,000 friends, but most users have between 150 and 250, although many of these will be acquaintances and some will be strangers." Actually, people with more Facebook friends tend to have more in-person friends as well.

As for a friendship formula, Dunbar suggests every-other-day contact for your very close friends and once a week for your next five closest pals, either face-to-face or online. Once a month is enough for the next 15, every six months for the next 50, and once a year for the rest of the group.

The exception is close friendships from your younger days — "you can often pick these relationships up exactly where you left off, even after decades."

Q: Are you a "morning person"? Can science explain why you might be a lark rather than an owl?

A: It has to do with your circadian system, that brain region of 20,000 nerve cells that regulates everything from hormone levels and when you digest food to when you feel sleepy, says Sonia Ancoli-Israel of UC-San Diego's Sleep Medicine Center, as reported by Nathan Reese in "Mental Floss" magazine. Larks (think of morning birds) are "phase advanced," feeling tired early in the evening, while owls are "phase delayed," feeling tired later at night.

As you've probably observed, people's circadian rhythms change over time, with babies waking at dawn but teens struggling to get out of bed by noon. As adults get older, mornings usually get easier. Genetics plays a key role here: "In 2012, scientists discovered a single nucleotide near a gene called 'Period 1' that determines whether you're an owl, a lark, or in between."

Since research suggests that early risers have a mental edge, to become more lark-like, stick to a regimented sleep schedule and avoid disruptive evening light before you call it a night, Reese says.

Q: What striking thing happens when you put on specially tinted lenses incorporating the latest color vision science and optical technology? What if you're color-blind, or more accurately, color-deficient?

A: With these ordinary looking EnChroma lenses, colors appear more vibrant, saturated and full. According to the website, "colorful objects, such as flowers, colorful paint and fabrics, food and traffic signs suddenly 'pop' with a heightened purity and intensity. Experiences like a rainbow or a sunset, seen for the first time with these lenses, are magically transformed beyond any rational description."

A little background first: People with color vision deficiency have red and green photopigments that overlap more than normal, "analogous to how two adjacent radio stations might bleed together and make a mess of conflicting information ..."

Drawing on perceptual psychophysics, the EnChroma team was able to simulate the appearance of thousands of colors and see what happens to a visual system affected by any given filter. They eventually produced a lens that improves the signal separation of affected retinal cone cells and provides better color vision.

Though not a cure for color blindness, as the website says, EnChroma can serve as an optical assistive device for most deficient observers.

Send STRANGE questions to brothers Bill and Rich at


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