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Image: Rock paper scissors contest
Mark Blinch  /  Reuters file
Two contestants compete in the 2006 International World Rock Paper Scissors Championships in Toronto. Experienced players tend to throw out Paper to counter a rookie's Rock — but that leaves them open to a Scissors parry, as shown here.
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updated 8/16/2011 1:12:46 PM ET 2011-08-16T17:12:46

In the game "Rock, Paper, Scissors," two opponents randomly toss out hand gestures, and each one wins, loses or draws with equal probability. It's supposed to be a game of pure luck, not skill — and indeed, if humans were able to be perfectly random, no one could gain an upper hand over anyone else.

There's one problem with that reasoning: Humans are terrible at being random.

Our pathetic attempts to appear uncalculating are, in fact, highly predictable. A couple of recent studies have provided insights into the patterns by which people tend to play "Rock, Paper, Scissors" (and why). Abide by them, and you'll be riding shotgun and eating the bigger half of the cookie for the rest of your life.

According to Graham Walker, veteran player and five-time organizer of the World Rock, Paper Scissors Championships, there are two paths to victory in RPS: Eliminating one of your opponent's options — for example, influencing her not to play Paper — and forcing her to make a predictable move.

In both cases, Walker wrote on the website of the World RPS Society, "the key is that it has to be done without them realizing that you are manipulating them."

Rookies rock
Those two overarching strategies can be translated into executable moves, starting with the opening one. Expert players have observed that inexperienced ones tend to lead with Rock. Walker speculates that this may be because they view the move as strong and forceful. Either way, remember the mantra "Rock is for rookies," and simply throw Paper at the outset of a game to earn an easy first victory.

"Rock is for rookies" should be kept in mind against more experienced players, too. They won't lead with Rock — it's too obvious — so use Scissors against them. This throw will either beat Paper or tie with itself.

Double trouble
If your opponent makes the same move twice in a row, they almost certainly won't make that move a third time. "People hate being predictable, and the perceived hallmark of predictability is to come out with the same throw three times in row," Walker wrote. [Why Aren't We Smarter?]

With that option eliminated, you're guaranteed either a victory or a stalemate in the next round. If you see a "two-Scissor run," for example, your opponent's next move will be either Rock or Paper. If you throw Paper, then, you'll either beat Rock or play to a draw.

Mind tricks
Like a Jedi, you can use the power of suggestion to influence your opponent's next move. When discussing a game, for example, gesture over and over again with the move that you want your opponent to play next. "Believe it or not, when people are not paying attention their subconscious mind will often accept your 'suggestion,'" Walker wrote.

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This trick may work because of humans' tendency to imitate one another's actions. A recent study on decision-making in "Rock, Paper, Scissors," published in the July 2011 issue of the Proceedings of the Royal Society B, found that players often imitate their opponents' last moves. Human mimicry seems to be involuntary.

Announcing your next move before a round starts also seems to be an effective mind trick, though it'll only work once. If you say you're going with Paper, for example, your opponent thinks you won't, Walker explained. Subconsciously, they'll shy away from Scissors (which beats Paper), and choose Rock or Paper instead. When you do end up throwing Paper, you'll score a victory or a tie.

Don't call it a comeback
According to Walker, your opponent will often try to come back from a loss or tie by throwing the move that would have beaten his last one. If he lost using Rock, for example, he'll likely follow up by throwing Paper. Knowing this, you can decide what move to follow with yourself.

Interestingly, monkeys show the same behavioral pattern. In a study detailed in the May 2011 issue of the journal Neuron, researchers at Yale found that rhesus monkeys trained to play "Rock, Paper, Scissors" tended to react to a loss by playing the move that would have won in the previous round. This suggests that monkeys, like humans, are capable of analyzing past results and imagining a different outcome, the researchers said. [The 6 Craziest Animal Experiments]

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Humans can take the logic one step further, by imagining what their opponents might be imagining.

Low blow
There's one more ploy to fall back on — that is, if you're willing to sacrifice your honor and integrity for a victory.

"When you suggest a game with someone, make no mention of the number of rounds you are going to play. Play the first match and if you win, take it is as a win. If you lose, without missing a beat start playing the 'next' round on the assumption that it was a best two out of three. No doubt you will hear protests from your opponent, but stay firm and remind them that 'no one plays best of one,'" Walker wrote. A low blow, but a smart one.

Had no idea so much strategy was possible in "Rock, Paper, Scissors"? The rules of the game itself may be simple, but the human mind is not.

Follow Natalie Wolchover on Twitter @nattyover. Follow Life's Little Mysteries on Twitter @llmysteries, then join us onFacebook.

© 2013 LifesLittleMysteries.com. All rights reserved. More from LifesLittleMysteries.com.

Explainer: The 2011 Weird Science Awards

  • Image: Stone Age sex toy; Beer and civilization; Slime-mold transit; Cricket testicles
    SNHB / U. Penn / AAAS / U. Derby

    Sex, booze and strange animal tricks: You had to know the 2011 Weird Science Awards would hit on those themes. After all, past award winners have included scientists' successful quest to reattach rabbit penises, a 2,700-year-old marijuana stash and glow-in-the-dark kitties. This year, msnbc.com users were asked to select the weirdest stories from a list of 30 nominees. Click ahead to count down the top 10 selections, plus some bonus picks.

    — Alan Boyle, msnbc.com science editor

  • 10. Oops! Maya doomsday date corrected

    El Castillo
    MSNBC file
    The El Castillo pyramid at Chichen Itza in Mexico is one of the monuments left behind by the Maya.

    Are we having doomsday yet? Some folks say the ancient Maya calendar's "Long Count" runs out on Dec. 21, 2012, and that a world-changing crisis will occur at that time. Other folks, including the modern-day Maya, say that's just a load of llama crap ... and that 12/22/2012 will merely mark the start of a new calendar cycle.

    And then there's Gerardo Aldana, a professor at the University of California at Santa Barbara, who says they're all probably wrong.

    Aldana contends that the calculations we've used to match up the Maya calendar to our modern reckoning could be off by as much as 50 to 100 years, and that the Long Count may have already ended. If Aldana is right, the timetable for the apocalypse may already be up. Which might explain why "Apocalypto" director Mel Gibson's been acting so weird lately.

  • 9. Why it's OK for birds to be gay

    Image: Gay geese
    Dreamstime
    Nearly one-fifth of all long-term greylag geese couples are gay, composed of two males.

    Scientists have found more than 130 bird species that engage in some sort of same-sex hanky-panky — and the males in some of those species, such as penguins and greylag geese, occasionally form long-term sexual relationships with each other.

    That's presented a puzzle for some evolutionary biologists, because same-sex relationships would seem to reduce the birds' chances of reproductive success. Believe it or not, gay birds are quite a research topic ... not that there's anything wrong with that.

    Geoff MacFarlane, a biologist at the University of Newcastle in Australia, and colleagues reviewed studies of 93 bird species and suggested that there was a relationship between the rearing of young and same-sex mating. Male homosexual behavior would be likelier if the females of the species took care of the chicks. "Homosexual behavior is more likely to be maintained and not be selected against than if you are a sex that cares a lot for offspring and only has one or few reproductive partners," MacFarlane said.

    Are you still curious? Find out why some scientists think mercury pollution may spark bird homosexuality, and learn more about the bizarre study of a homosexual necrophiliac duck.

  • 8. The race to create A.I. as smart as a cat

    NIH
    Are cats worried about the Pentagon's efforts to match their intelligence with an artificial brain? What do you think?

    Puss-Bob is not amused: He's heard the reports claiming that Pentagon-funded scientists are trying to create an artificial brain as intelligent as a cat, of course, but he realizes this is a grossly oversimplified description of the SyNAPSE project.

    He knows the real point of the research is to build electronic networks that mimic biological brains, using new types of devices known as memristors. Such networks could "learn" by taking in additional information from the environment and adapting accordingly.

    The technology could produce smarter robotic scout vehicles for the U.S. military, IEEE Spectrum reports. But Puss-Bob highly doubts that memristor-based neural networks will ever match the intelligence of cats. Dogs, maybe ... but not cats.

  • 7: 'Da Vinci code' in Mona Lisa's eyes?

    V.A Sole  /  CNRS via AP
    Leonardo da Vinci's "Mona Lisa" is examined with X-ray fluorescence spectroscopy.

    The Mona Lisa is one of the great masterpieces of the art world, but it's also a great generator of weird science. In past years, researchers have said that they've tracked down the inspiration for Leonardo da Vinci's portrait, found a nude version of the painting and figured out what Mona Lisa's voice sounded like.

    In 2010, Italy's national committee for cultural heritage claimed that Leonardo painted tiny, almost invisible letters in Mona Lisa's eyes. The committee's president, Silvano Vinceti, said the lines in one eye appear to form the initials "LV," perhaps standing for the artist's name. The other eye seems to contain the letters "CE" or perhaps "B." And still more letters and numbers were spotted in other areas of the painting.

    But are they really there? Several experts have said the committee is probably reading too much into the painting's patterns of tiny cracks. Among art historians, at least, this "Da Vinci Code" is no best-seller.

  • 6. Which came first, chicken or egg?

    Image: Chicken and egg
    USDA
    Which came first, the chicken or the egg? The scientific answer is problematic.

    Which came first? The chicken or the egg? The question is really more of a philosophical conundrum, like the old "immovable object vs. irresistible force" conflict. But in 2010, British research into the process of eggshell formation was heralded as providing a scientific answer to the riddle.

    Biologists from Sheffield and Warwick universities reported that ovocleidin-17, a protein found in a chicken's ovaries, played an essential role in building eggshells from calcium carbonate crystals. That led some chicken-or-egg philosophers to claim that the first chicken egg could exist only if it was created inside a chicken.

    Actually, it all depends on your definitions: We know that dinosaurs laid eggs, for example, so eggs clearly predate chickens. And if a prehistoric not-quite-chicken laid an egg that contained the first honest-to-goodness chicken, based on its genetic coding, do you count that as a chicken, or a chicken egg? Try using that one if you're ever captured by "Star Trek" androids.

  • 5. Giant storks may have fed on hobbits

    Inge van Noortwijk
    The extinct giant stork Leptoptilos robustus would have dwarfed the "hobbit" Homo floresiensis living on the Indonesian island of Flores.

    "The storks! The storks! They're eating Frodo!" J.R.R. Tolkien's "Lord of the Rings" saga might have had a horror-movie ending if it reflected the fossil evidence found on the Indonesian island of Flores.

    Flores is known as the site where scientists discovered the remains of a species of hominids known as Homo floresiensis. The creatures, which apparently went extinct about 12,000 years ago, have been nicknamed "hobbits" because of their short stature.

    Now paleontologists say they've unearthed wing and leg bones from carnivorous storks in the same cave where the Homo floresiensis bones were discovered. The storks, which apparently stood nearly 6 feet tall, could have fed on other birds as well as fishes and lizards — "and possibly in principle even small, juvenile hobbits, although we have no evidence for that," the Smithsonian Institution's Hanneke Meijer told LiveScience.

    What sound do giant storks make when they're swallowing? Gollum! Gollum!

  • 4. Cricket's testicles set world record

    University of Derby
    The male Tuberous bushcricket has testicles (shown here) that amount to 14 percent of its body weight.

    Now here's a bug with balls: The tuberous bushcricket's testicles account for 14 percent of its body weight, according to researchers at the University of Derby in England. That means the cricket's cojones are the largest in the animal world, based on proportion to total body mass.

    To put the cricket's statistics in perspective, the testicles of a man weighing 200 pounds (91 kilograms) with that ball-to-body ratio would weigh 28 pounds (12.7 kilograms). Or basically the weight of two bowling balls.

    Why would a cricket need testes that big? The researchers suggest that the large size lets male crickets capitalize quickly on breeding opportunities with multiple mates. But size is always relative, and often deceiving. Turns out that the runner-up in the ball-to-body competition is the humble fruit fly, with testes that make up more than 10 percent of body weight.

  • 3. Better transit design through ... slime mold?

    Image: Slime mold
    Science / AAAS
    The left image shows slime mold growing out to connect food sources laid out like a map of rail stations. After 26 hours, the mold resolved itself into an efficient network of tubes connecting the sources

    It's hard to imagine a scientific specialty that's weirder than slime mold, but researchers from Hokkaido University in Japan has been able to make the weird life form do some wonderful things.

    First, the scientists used slime mold's food-finding prowess to solve labyrinth puzzles. This year, they published research showing how the mold's growth patterns could reflect the optimal routes for mass transit links ... on a map where bits of food stood in for train stations. Those dubious achievements earned them not just one, but two Ig Nobel Prizes for silly science.

    The Hokkaido team isn't the only one working with the humble organism: British scientists say they've constructed a rudimentary slime-mold computer nicknamed the Plasmobot. So where does America stand in the race to harness slime mold? And what are we going to do about the slime gap?

  • 2. How beer sparked civilization

    Image: ancient vessel
    University of Pennsylvania
    Fragments of a jar unearthed in Iran contain the chemical residues of beer from more than 5,000 years ago.

    Some people might say the invention of fire sparked the rise of civilization. But Brian Hayden, an archaeologist at Simon Fraser University, suggests that another innovation may have played a crucial role: beer.

    The age of agriculture dawned about 11,500 years ago when Neolithic peoples began domesticating wild grains such as barley and rice. Hayden is among a number of archaeologists who say the motivation for domesticating those cereals might have been to brew alcoholic drinks for ceremonial use. "It's not that drinking and brewing by itself helped start cultivation, it's this context of feasts that links beer and the emergence of complex societies," Hayden says.

    The earliest chemical evidence for beer comes from residues inside a jar excavated in Iran that is dated to between 3400 and 3100 B.C. Other evidence suggests that beer gave ancient Africans a healthy dose of antibiotics, and that women took on the primary role for brewing beer in ancient Peru. For still more, check out our interactive gallery of ancient drinks.

  • 1. Stone Age carving may be ancient sex toy

    Image: Bone carving
    Peter Zetterlund  /  Swedish National Heritage Board

    The top vote-getter in the 2010 Weird Science Award competition may not be totally suitable for work ... but hey, this is archaeology, right? Researchers suspect that a carved piece of antler bone, found at a Stone Age site in Sweden that goes back as far as 6000 B.C., might have been an ancient sex toy.

    The object is about 4 inches long and an inch wide, with a knobby end as well as a pointy end. The pointy end suggests that despite its phallic appearance, the bone could have been used for chipping flakes of flint. Sigmund Freud is said to have observed that "sometimes a cigar is just a cigar," and sometimes a Stone Age tool is just a Stone Age tool.

    Even if the antler bone is judged to be a sex toy, it's not the oldest of its type: A polished stone phallus found in Germany is thought to be about 28,000 years old, while a 35,000-year-old female figure with exaggerated breasts could be considered the world's oldest-known porn.

  • Weirdly honorable mentions

    Image: Mouse
    Stephanie Pappas / LiveScience
    This mouse is among many that was born with genetic contributions from two male mice.

    Even though we offered up a long list of nominees for the Weird Science Awards, there are always some additional discoveries that deserve recognition. Here are four honorable mentions for 2010:

    • Mice with two dads: Researchers reprogrammed mouse cells and then used unconventional breeding tricks to produce some cute babies with genetic contributions from two male mice (but carried to term by mommy mice, of course). The experiment suggested a method by which same-sex human couples could eventually have genetic progeny.
    • Chimps with stick dolls: Female chimpanzees have been observed in the wild cuddling and playing with sticks and small logs, much like human children do. In contrast, such behavior has not yet been seen among male chimps, leading researchers to wonder whether gender differences in styles of play extend beyond humans to other species.
    • Mice that sing like birds: In the course of developing new breeds of genetically engineered mice, Japanese researchers happened upon a mouse that made tweeting noises like a bird. The tweeting trait could be passed along to the generations that followed, and the lab says it now has more than 100 "singing mice." Listen to the chirping mice on YouTube.
    • 8-year-olds publish scientific paper: One of the more unusual papers published in Biology Letters was illustrated with diagrams that looked as if they were scrawled by elementary-school students. That's because they were. The peer-reviewed report, written by 8- to 10-year-olds from Blackawton Primary School in Devon, England, represented a "genuine advance" in the study of bumblebee vision, the Royal Society said.

    For still more scientific strangeness, review the 2010 Weird Science Awards.

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