The self-help industry is mired in ideas about positive thinking that are at best ineffective and at worst destructive. If you want to be more confident or successful, says Richard Wiseman , the best thing to do is act the part

For years self-help gurus have preached the same simple mantra: if you want to improve your life then you need to change how you think. Force yourself to have positive thoughts and you will become happier. Visualise your dream self and you will enjoy increased success. Think like a millionaire and you will magically grow rich. In principle, this idea sounds perfectly reasonable. However, in practice it often proves ineffective.

Take visualisation. Hundreds of self-improvement books encourage readers to close their eyes and imagine their perfect selves; to see themselves in a huge office at the top of the corporate ladder, or sipping a cocktail as they feel the warm Caribbean sand between their toes. Unfortunately, research suggests this technique does not work.

In one study led by Lien Pham at the University of California, students were asked to spend a few moments each day visualising themselves getting a high grade in an upcoming exam. Even though the daydreaming exercise only lasted a few minutes, it caused the students to study less and obtain lower marks. In another experiment led by Gabriele Oettingen from New York University, graduates were asked to note down how often they fantasised about getting their dream job after leaving college. The students who reported that they frequently fantasised about such success received fewer job offers and ended up with significantly smaller salaries.

Why should this be so? Maybe those who fantasise about a wonderful life are ill-prepared for setbacks, or become reluctant to put in the effort required to achieve their goal. Either way, the message is clear – imagining the perfect you is not good for your life.

However, when it comes to change, the message is not all gloom and doom. Decades of research show that there is indeed a simple but highly effective way to transform how you think and feel. The technique turns common sense on its head but is grounded in science. Strangely, the story begins with a world-renowned Victorian thinker and an imaginary bear.

Working at Harvard University in the late 19th century, William James, brother of the novelist Henry James, was attracted to the unconventional, often walking around campus sporting a silk hat and red-checked trousers, and describing his theories using amusing prose ("As long as one poor cockroach feels the pangs of unrequited love, this world is not a moral world"). This unconventional approach paid off. First published in 1890, James's two-volume magnum opus The Principles of Psychology is still required reading for students of behavioural science.

Towards the end of the 1880s, James turned his attention to the relationship between emotion and behaviour. Our everyday experience tells us that your emotions cause you to behave in certain ways. Feeling happy makes you smile, and feeling sad makes you frown. Case closed, mystery solved. However, James became convinced that this commonsense view was incomplete and proposed a radical new theory.

James hypothesised that the relationship between emotion and behaviour was a two-way street, and that behaviour can cause emotion. According to James, smiling can make you feel happy and frowning can make you feel sad. Or, to use James's favourite way of putting it: "You do not run from a bear because you are afraid of it, but rather become afraid of the bear because you run from it."

James's theory was quickly relegated to the filing drawer marked "years ahead of its time", and there it lay for more than six decades.

Throughout that time many self-help gurus promoted ideas that were in line with people's everyday experiences about the human mind. Common sense tells us that emotions come before behaviour, and so decades of self-help books told readers to focus on trying to change the way they thought rather than the way they behaved. James's theory simply didn't get a look-in.

However in the 70s psychologist James Laird from Clark University decided to put James's theory to the test. Volunteers were invited into the laboratory and asked to adopt certain facial expressions. To create an angry expression participants were asked to draw down their eyebrows and clench their teeth. For the happy expression they were asked to draw back the corners of the mouth. The results were remarkable. Exactly as predicted by James years before, the participants felt significantly happier when they forced their faces into smiles, and much angrier when they were clenching their teeth.

Subsequent research has shown that the same effect applies to almost all aspects of our everyday lives. By acting as if you are a certain type of person, you become that person – what I call the "As If" principle.

Take, for example, willpower. Motivated people tense their muscles as they get ready to spring into action. But can you boost your willpower by simply tensing your muscles? Studies led by Iris Hung from the National University of Singapore had volunteers visit a local cafeteria and asked them to try to avoid temptation and not buy sugary snacks. Some of the volunteers were asked to make their hand into a fist or contract their biceps, and thus behave as if they were more motivated. Amazingly, this simple exercise made people far more likely to buy healthy food.

The same applies to confidence. Most books on increasing confidence encourage readers to focus on instances in their life when they have done well or ask them to visualise themselves being more assertive. In contrast, the As If principle suggests that it would be much more effective to simply ask people to change their behaviour.

Dana Carney, an assistant professor at Columbia Business School, led a study where she split volunteers into two groups. The people in one group were placed into power poses. Some were seated at desks, asked to put their feet up on the table, look up, and interlock their hands behind the back of their heads. In contrast, those in the other group were asked to adopt poses that weren't associated with dominance. Some of these participants were asked to place their feet on the floor, with hands in their laps and look at the ground. Just one minute of dominant posing provided a real boost in confidence.

The researchers then turned their attention to the chemicals coursing through the volunteers' veins. Those power posing had significantly higher levels of testosterone, proving that the poses had changed the chemical make-up of their bodies.

The As If principle can even make you feel younger. Harvard psychology professor Ellen Langer has conducted many high-profile experiments; one of her most striking involved using the As If principle to turn back the hands of time.

In 1979 Langer recruited a group of men in their 70s for a "week of reminiscence" at a retreat outside Boston. Before the study started, Langer tested the men's strength, posture, eyesight and memory.

She then encouraged the men to act as if they were 20 years younger. When they arrived at the retreat, for instance, there was no one there to help them off the bus and they had to carry their suitcases inside. In addition, the retreat had not been not equipped with the type of rails and other movement aids they had at home. After unpacking, everyone was assembled in the main room of the retreat. Surrounded by various objects from the 50s, including a black-and-white television and a vintage radio, Langer informed the participants that for the next few days all of their conversations about the past had to be in the present tense, and that no conversation must mention anything that happened after 1959.

Within days, Langer could see the dramatic effect of behaving As If. The participants were now walking faster and were more confident. Within a week several of the participants had decided that they could now manage without their walking sticks. Langer took various psychological and physiological measurements throughout the experiment and discovered that the group now showed improvements in dexterity, speed of movement, memory, blood pressure, eyesight and hearing. Acting as if they were young men had knocked years off their bodies and minds.

More than a century ago William James proposed a radically different approach to change. Decades of research has shown that his theory applies to almost every aspect of everyday life, and can be used to help people feel happier, avoid anxiety and worry, fall in love and live happily ever after, stay slim, increase their willpower and confidence, and even slow the effects of ageing.

So sit up straight and take a deep breath. It is time to rip up the rule book and embrace the truth about change.

How to change

Action speaks loudest

Here are 10 quick and effective exercises that use the As If principle to transform how you think and behave.

HAPPINESS: Smile

This is the granddaddy of them all. As Laird's study demonstrated, smile and you will feel happier. To get the most out of this exercise, make the smile as wide as possible, extend your eyebrow muscles slightly upward, and hold the resulting expression for about 20 seconds.

WILLPOWER: Tense up

As Hung's experiments show, tensing your muscles boosts your willpower. Next time you feel the need to avoid that cigarette or cream cake, make a fist, contract your biceps, press your thumb and first finger together, or grip a pen in your hand.

DIETING: Use your non-dominant hand

When you eat with your non-dominant hand you are acting as if you are carrying out an unusual behaviour. Because of that you place more attention on your action, do not simply consume food without thinking about it, and so eat less.

PROCRASTINATION: Make a start

To overcome procrastination, act as if you are interested in what it is that you have to do. Spend just a few minutes carrying out the first part of whatever it is you are avoiding, and suddenly you will feel a strong need to complete the task.

PERSISTENCE: Sit up straight and cross your arms

Ron Friedman from the University of Rochester led a study where volunteers were presented with tricky problems to see how long they persevered. Those who sat up straight and folded their arms struggled on for nearly twice as long as others. Make sure your computer monitor is slightly above your eye-line and, when the going gets tough, cross your arms.

CONFIDENCE: Power pose

To increase your self-esteem and confidence, adopt a power pose. If you are sitting down, lean back, look up and interlock your hands behind your head. If you are standing up, then place your feet flat on the floor, push your shoulders back and your chest forward.

NEGOTIATION: Use soft chairs

Hard furniture is associated with hard behaviour. In one study Joshua Ackerman at the MIT Sloan School of Management had participants sit on either soft or hard chairs and then negotiate over the price of a used car. Those in the hard chairs offered less and were more inflexible.

GUILT: Wash away your sins

If you are feeling guilty about something, try washing your hands or taking a shower. Chen-Bo Zhong from the University of Toronto discovered that people who carried out an immoral act and then cleaned their hands with an antiseptic wipe felt significantly less guilty than others.

PERSUASION: Nod

If people nod while they listen to a discussion they are more likely to agree with the points being made. When you want to encourage someone to agree with you, subtly nod your head as you chat with them. Research led by Gary Wells of Iowa State University shows that they will reciprocate the movement and find themselves strangely attracted to your way of thinking.

LOVE: Open up

Couples in love talk about the more intimate aspects of their lives. Research carried out by Robert Epstein, founder of the Cambridge Centre for Behavioural Studies, shows that the opposite is also true – more intimate chat makes people feel attracted to each other. If you are out on a date, get the other person to open up by asking what advice they would give to their 10-year-old self, or what one object they would save in a house fire.

About the author

Richard Wiseman's first career was as a professional magician and he was once one of the youngest members of the Magic Circle. He studied at UCL and the University of Edinburgh and is now Britain's only professor for the public understanding of psychology, based at the University of Hertfordshire. He is also a fellow of the US-based Committee for Skeptical Inquiry and in 2001 he led an experiment to find the world's funniest joke. His previous books have included a study of luck, The Luck Factor, and 59 Seconds, described by the science writer Simon Singh as "a self-help guide based on proper research". Rip It Up delves further into the science of self-help. The book is so titled because Wiseman wants readers to tear up the book's pages as they read them: "The book is all about people changing their behaviour," he says. "To emphasise this key message I am inviting readers to do something that they probably have never done. Each time, readers will be changing their behaviour and so altering how they think and feel."