Through the Language Glass
by Guy Deutscher.
Metropolitan Books
(Macmillan), 2010 ($28)

Do we see the world differently depending on which language we speak? In the 19th century researchers assumed that people were unable to grasp concepts if there were no words in their language to describe them. This idea was largely debunked, however, in the late 20th century, when linguists concluded that it is possible to describe any concept in any language, given enough effort and time. But as Guy Deutscher argues in his new book, our mother tongue may still shape our worldviews, not because of what its speakers are able to express but because of what its speakers are forced to express.

Although Deutscher's book starts slowly—the first half is more history than current science—the pace picks up as he describes intriguing linguistic idiosyncrasies and explains their potential effects on cognition. For one thing, linguistic rules influence how much information a person must convey. In English, you might be able to discreetly tell a friend that you “spent the evening with your neighbor,” and you aren't forced to reveal whether this neighbor happened to be a man or a woman. The French and Spanish languages, however, as well as others, including German and Russian, have different words for “female neighbor” and “male neighbor,” so linguistic convention would require you to reveal that potentially interesting detail.

Guugu Yimithirr, an Aboriginal Australian language, requires speakers to develop a nearly perfect sense of direction. In its conventions, instead of right, left, front and back, a constant, almost intuitive knowledge of north, south, east and west is used to convey all spatial information. You might be warned about “the ant to the north of your foot” or told that “the fish is sold in the northeast corner of the store.” Deutscher argues that this compasslike sense of direction affects memory and perception. For instance, if two identical photographs are placed side by side, English and Guugu Yimithirr speakers will say they look the same. But if one photograph is rotated 90 degrees to the left and the other is rotated 90 degrees to the right, the Guugu Yimithirr speaker will no longer view them as identical, because the objects they portray are facing entirely different directions. “Two realities that for us can look identical will appear different to them,” Deutscher writes.

Finally, the words that a particular language uses to describe colors can affect visual perception. As Deutscher explains, studies suggest that people can see a difference between colors that have different names more quickly than they can detect a difference between two shades of the same color. Ultimately, Deutscher admits, it's unclear exactly how strongly these—or other as yet undiscovered—habits of speech might affect us. But language may well be another lens distorting our view of the world. —Melinda Wenner Moyer

Your Brain on Food—How Chemicals Control Your Thoughts and Feelings
by Gary L. Wenk.
Oxford University Press, 2010 ($29.95)

Nutmeg induces LSD-like hallucinations. That is, if you eat an entire container in one sitting, according to neuroscientist Gary L. Wenk in his book Your Brain on Food. He also explains why we crave chocolate—it contains fats that cause our bodies to release mood-enhancing chemicals—and why coffee may be good for us: drinking five to six cups a day may prevent Parkinson's disease and diabetes.

But if you're hoping the book will live up to its title and explain how a range of foods alters your brain, you'll be sorely disappointed. Wenk spends very little time discussing food beyond these brief mentions of spices, coffee and chocolate. Instead he focuses almost exclusively on how the brain responds to drugs.

If you can get over the misleading title, the book makes for an interesting read. Wenk describes how cocaine, marijuana and LSD alter the flow of brain chemicals such as dopamine and serotonin. Wenk explains, for example, that the brain's response to marijuana may alter as we age. In the young brain, marijuana impairs the ability to retain memories because of the chemical THC. THC binds to and activates specific neuronal receptors that control memory and concentration. But studies suggest that as we age, the drug may actually have the reverse effect, helping the brain preserve memories. Although Wenk does not describe the precise reason why, he suggests that the drug reduces inflammation and possibly even stimulates new brain cells to form.

Wenk also links mind-altering drugs to spirituality. In ancient times, religious leaders regularly used hallucinogenic plants in an attempt to communicate with the gods. Recent studies suggest these plants cause hallucinations because they reduce serotonin sensitivity, causing the brain to become overloaded with sensory information. This confusion can create the sensation that one is floating in space or communicating with a higher power. To support this idea, several studies have even shown that people whose brains contain a low number of a type of serotonin receptor tend to be more religious.

Tidbits such as this keep Wenk's journey through your brain intriguing and highlight how easy it is for the chemicals we ingest and those we produce naturally to modify the way we think, feel and act. —Nicole Branan

On Second Thought: Outsmarting Your Mind’s Hard-Wired Habits
by Wray Herbert.
Crown Publishers, 2010 ($25)

Baby sea turtles don't sit around pondering what to do after they hatch—they head straight for the safety of the ocean. Like sea turtles, humans rely on their instincts to survive, although we have evolved a more cerebral set of tools to do so. As Wray Herbert, a longtime contributor to Scientific American Mind, explains in his new book On Second Thought, we depend on hardwired mental shortcuts called heuristics to help us make decisions and solve problems efficiently.

For instance, when we walk into a new restaurant, we don't have to waste time figuring out what to do next. We instinctively know to wait for a table, sit down, look at the menu and then order our food. Similarly, when faced with an endless choice of cereals, we reflexively reach for the product we know we like instead of pacing up and down the aisle comparing every last box.

But sometimes heuristics can lead to illogical reasoning or bad decisions. Consider what Herbert calls the cooties heuristic—an aversion to something we believe is contaminated. This mental shortcut helps us, and helped our ancestors, avoid infection and food poisoning—but we can take it too far. In one study, psychologists asked people whether they would be willing to wear a sweater Adolf Hitler once wore. Although no such sweater exists and no article of clothing could transfer Hitler's personality, most participants adamantly refused.

And there's the scarcity heuristic, which says that if something is rare it must be valuable and, conversely, if something is valuable it must also be scarce—a guideline that makes sense for prized materials, such as gold or precious reserves of food in lean times. Still, this rule of thumb can lead us to hopeless conclusions. The scarcity heuristic helps to explain why we often think that a good man or woman is hard (if not impossible) to find. Using this logic, some people just give up the search for a mate, even though they couldn't possibly have exhausted every option.

“Heuristics are neither good nor bad all the time,” Herbert admits. “It's all about getting the balance right.” The key to that balance, according to Herbert, is recognizing that mental shortcuts exist in the first place. To help us become aware of our snap judgments and avoid the irrational ones, Herbert divulges 20 different heuristics in 20 chapters and discusses their pros and cons.

At times, On Second Thought feels like a rundown of mental heuristics with only vague advice on how to avoid the pitfalls. So skipping to the particular topics that interest you most may be wise. In other words, take your own shortcuts. —Ferris Jabr

How Many Friends Does One Person Need? Dunbar’s Number and Other Evolutionary Quirks
by Robin Dunbar.
Harvard University Press, 2010 ($27.95)

If you find relationships challenging to cultivate and maintain, then you are in good company. In his new book, evolutionary biologist Robin Dunbar argues that our ability to manage such complex social connections—love lives, work colleagues, childhood buddies and friendly acquaintances—is what drove humans to develop such large brains in the first place.

Dunbar finds support for this theory, dubbed the social intelligence hypothesis, by observing birds. He recently conducted studies in several species of birds and found a clear link between brain size and relationship type. Birds that mate for life have much larger brains relative to body size, whereas birds that live in promiscuous flocks have much smaller brains. Dunbar speculates that birds with smaller brains have many short-lived partners because they lack the mental prowess to form and maintain more complex emotional bonds.

Dunbar finds that apes and monkeys form lasting bonds and have a particularly big neocortex—a region of the brain that regulates emotions, awareness of others and language abilities. Humans form some of the most intricate and complex relationships of all. And our brains are high maintenance, consuming a whopping 20 percent of our energy.

Judging from human brain size and complexity, Dunbar calculates that a person's social group should incorporate about 150 people—this is the maximum number of relationships our brain can keep track of at one time. This figure, now graced with the name “Dunbar's number” takes different types of relationships into account. On one end of the spectrum, we have a core group of about five people we talk to once a week. On the other end, we have a group of around 100 acquaintances to whom we speak about once a year.

Dunbar's theory may appear to fall short when you think of the masses of people you know at your church or the hundreds of friends you have on social network sites such as Facebook, but Dunbar claims that the more friends you have beyond his number, the less likely you are to know much about them—or if you can even call them friends. —Frank Bures