Science

40 Studies That Changed Psychology

A century of surprises.

Forty Studies That Changed Psychology by Roger Hock is a summary of 40 major psychology studies. I’ve squeezed its 300 pages into about 10.

PsyBlog lists a few more studies. And don’t forget the Most Important Psychological Study That Has Never Been Done.

Biology and human behavior

Two-Brained

Gazzaniga studied patients whose brains had been cut down the middle. Their intelligence, personality, and emotions hadn’t changed.

Each half of your brain has special skills. Your left brain is better at speaking, writing, reading, and math. Your right brain is better at recognizing faces, understanding spatial relationships, symbolic reasoning, and art.Gazzaniga (1967). The split brain in man. Scientific American, 217(2), 24-29. [Video.]

More Experience = Bigger Brain

Lab rats were put in one of three environments. Some went to a normal cage with other rats. Others went to an “impoverished” cage. These had no other rats. Others went to an “enriched” cage. These had other rats and playthings.

After several weeks, researchers killed the rats and examined their brains.

Compared to impoverished rats, enriched rats had a thicker cortex, larger neurons, and more brain activity. Brains are changed by experience.Rosenzweig, Bennet, & Diamond (1972). Brain changes in response to experience. Scientific American, 226 (2), 22-29.

Nature vs. Nurture

Researchers compared identical twins reared apart to identical twins reared together. They compared the twins’ intelligence, personalities, families, and more. The point was to find out which traits are mostly due to nature, and which are mostly due to nurture.

The basic findings? IQ is mostly genetic. (But don’t worry. That’s only one kind of “smarts.”) Other results keep coming in.Bouchard, Lykken, McGue, Segal, & Tellegen (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250, 223-229.

Depth Perception

Researchers tested animals and infants to see if they were born with depth perception.

It is inborn, but it’s different in different species. It depends on a species’ needs. Certain animals can perceive depth right away. Humans can’t until after 6 months. Animals that don’t use sight much don’t have it at all.Gibson & Walk (1960). The “visual cliff.” Scientific American, 202 (4), 67-71.

Perception and consciousness

Perception is Learned

Turnbull watched a primitive people who lived only in a jungle. He took one of them, Kenge, where he had never been before. Outside the jungle. Kenge had never seen distance before. The jungle was too dense.

Kenge thought some bison were insects. They looked small from so far away. Kenge thought they were small.

Turnbull drove him to the giant bison. Kenge thought some magic had grown them from tiny to huge.

Some ideas (like size constancy) may be learned, not inborn.Turnbull (1961). Some observations regarding the experiences and behavior of the BaMbuti Pygmies. American Journal of Psychology, 74, 304-308.

We Need Dreams

Dement kept subjects awake for a long time. When finally allowed to sleep, the subjects did “extra” dreaming to “catch up.” We need to dream.Dement (1960). The effect of dream deprivation. Science, 131, 1705-1707.

Dreaming is Physiological

Researchers studied animal sleep. Findings? You are paralyzed while dreaming, probably to protect sleep. REM happens on a regular schedule. All mammals cycle between REM and non-REM sleep. The bigger the mammal, the slower the cycle.

Dreaming is started by our bodies, not our thoughts. Maybe dreaming is the brain’s attempt to organize your memories.Hobson & McCarley (1977). The brain as a dream-state generator: An activation-synthesis hypothesis of the dream process. American Journal of Psychiatry, 134, 1335-1348.

Hypnosis

Spanos summarized hypnosis studies. He found that hypnosis is not an altered state. Instead, hypnotic behavior is the result of motivated, goal-directed social behavior. Spanos de-mystified hypnosis.Spanos (1982). Hypnotic behavior: A cognitive, social, and psychological perspective. Research Communications in Psychology, Psychiatry, and Behavior, 7, 199-213.

Learning and conditioning

Salivating Dogs

Pavlov’s famous study with salivating dogs introduced classical conditioning.

Ring a bell each time you feed your dog. The dog will soon start salivating when it hears a bell ring, even if there isn’t any food.Pavlov (1927). Conditioned reflexes. London: Oxfor University Press.

Little Emotional Albert

Watson and Rayner’s Little Albert experiment showed that classical conditioning could also control feelings.Watson & Rayner (1920). Conditioned emotional responses. Journal of Experimental Psychology, 3, 1-14.

Radical Behaviorism

This article summarized Skinner’s radical behaviorism. The theory said that all behavior could be explained by its consequences. Behaviorism has since died, but it ruled psychology for decades.Skinner (1948). Superstition in a pigeon. Journal of Experimental Psychology, 38, 168-172.

Watch and Learn

Bandura and others theorized that behavior was learned by watching others. For example, children who watch their parents being angry are more likely to be angry themselves.Bandura, Ross, & Ross (1961). Transmission of aggression through imitation of aggressive models. Journal of Abnormal and Social Psychology, 63, 575-582.

Intelligence, thoughts, and memory

What You Expect Is What You Get

This study gave us the idea of the self-fulfilling prophecy: you get what you expect. When teachers expected students to perform better, they did. But this works better for younger children than older children.Rosenthal & Jacobson (1966). Teachers’ expectancies: Determinates of pupils’ IQ gains. Psychological Reports, 19, 115-118.

Many Ways to be Smart

Gardner thought there were many types of intelligence, not just the one measured by IQ. Using strict criteria, Gardner identified 8 intelligences. Linguistic: Shakespeare, Woody Allen. Musical: Mozart, Paul McCartney. Logical-mathematical: Einstein, Carl Sagan. Spatial: Picasso, Frank Lloyd Wright. Bodily-kinesthetic: Charlie Chaplin, Michael Jordon. Interpersonal: Ghandi, Oprah. Intrapersonal: Plato, Henry David Thoreau. Naturalist: Charles Darwin, Jane Goodall.

Gardner changed the question. It’s not “How smart are you?” It’s “How are you smart?”Gardner (1983). Frames of mind: The theory of multiple intelligences. New York: Basic Books.

Thoughts Influence Behavior

At the time, behaviorism ruled psychology. Psychologists ignored the role of our thoughts. Tolman used a few experiments with rats to show that thoughts, not just environmental consequences, can effect behavior.Tolman (1948). Cognitive maps in rats and men. Psychological Review, 55, 189-208.

Creating Memories

Loftus showed that leading questions can “create” false memories. (“How many people were in the car that was speeding?” instead of “Was the car speeding?”) Memories are not just recalled, but can be made.Loftus (1975). Leading questions and the eyewitness report. Cognitive Psychology, 7, 560-572.

Development

Love and Attachment

Monkeys were given one of two surrogate mothers. One mother had a smooth & soft rubber body, a milk-giving breast, and a lightbulb inside for warmth. Another mother was identical but had instead a wire mesh body. One mother was able to provide contact comfort, the other was not.

Results? Monkeys chose a mother based on contact comfort, not the meeting of biological needs like thirst and hunger. Comforting touch is crucial for loving attachment.Harlow (1958). The nature of love. American Psychologist, 13, 673-685.

Child Development

Piajet found that we don’t develop our mental abilities purely through learning, but that they actually develop in the brain as we age. Thus, no 6-year-old can think abstractly, no matter how much he is taught.Piaget (1954). The development of object concept: The construction of reality in the child (pp. 3-96). New York: Basic Books.

Moral Development

Kohlberg argued that we acquire morality in developmental stages. During premorality, punishment works. During role-conformity, we do what pleases others and mantains order. Under self-morality, we take on our culture’s values and form our own.Kohlberg (1963). The development of children’s orientations toward a moral order: Sequence in the development of moral thought. Vita Humana, 6, 11-33.

Happy to Be in Control

Nursing home patients given responsibility for their own living setup were much happier and healthier than those whose setup was made for them. A sense of control over one’s own life promotes happiness.Langer & Rodin (1976). The effects of choice and enhanced personal responsibility for the aged: A field experiment in an institutional setting. Journal of Personality and Social Psychology, 34, 191-198.

Emotion and motivation

Sex

Masters and Johnson studied thousands of people having sex in their labs. Now that’s research!

They reported that (a) sexual response happens in four stages: excitement, plateau, orgasm, and resolution. (b) Average penis size is 3″ flaccid and 6″ erect. (c) Flaccid size does not predict erect size. (d) Penis size is a minor factor in sexually stimulating a woman. (e) After orgasm men cannot orgasm again for some time. Women can orgasm again right away.Masters & Johnson (1966). Human sexual response. Boston: Little, Brown.

Faces of Emotion

Researchers studied a remote tribe that had never seen movies or pictures or worked with Westerners. Researchers told an emotional story and then asked subjects to point to a photo that showed the right emotion. They found that certain facial expressions are associated with certain emotions across all cultures.Ekman & Friesen (1971). Constants across cultures in the face and emotion. Journal of Personality and Social Psychology, 17, 124-129.

Stress and Illness

Researchers found the clear link between stress and illness so well known today. They also ranked the most stressful events. At the top of the list? Death of spouse, divorce, marital separation, jail term, and death of close family member.Holmes & Rahe (1967). The Social Readjustment Rating Scale. Journal of Psychosomatic Research, 11, 213-218.

Cognitive Dissonance

Festinger found that if you do or say something contrary to your attitude, you will tend to change your opinion to make it fit with what you said or did. This is an attempt to resolve “cognitive dissonance.”Festinger & Carlsmith (1959). Cognitive consequences of forced compliance. Journal of Abnormal and Social Psychology, 58, 203-210.

Personality

Control Yourself

Rotter found there are two kinds of people. Some think they control their own life. They’re called internals. Others think the world controls their life. They’re called externals. Internals quit smoking more easily, achieve more, and place safer bets.Rotter (1966). Generalized expectancies for internal versus external control of reinforcement. Psychological Monographs, 80, 1-28.

Male or Female?

Bem measured femininity and masculinity on different scales. He found that many people have male and female traits. Later studies showed that these persons actually have higher self-esteem, are more adaptable, and succeed more often in intimate relationships.Bem (1974). The measurement of psychological androgyny. Journal of Consulting and Clinical Psychology, 42, 155-162.

Personality and Heart Disease

Researchers found that personality traits—which lead to behavior—can affect health. A hurried, irritated, competetive person is more likely to have heart problems.Friedman & Rosenman (1959). Association of specific overt behavior pattern with blood and cardiovascular findings. Journal of the American Medical Association, 169, 1286-1296.

The One, the Many

This study showed that culture influences behavior. In some cultures, individuals are the focus. In others, groups are the focus. People in each culture behave differently.Triandis, Bontempo, Villareal, Asai & Lucca (1988). Individualism and collectivism: Cross-cultural perspectives on self-ingroup relationships. Journal of Personality and Social Psychology, 54, 323-338.

Psychopathology

Who’s Really Crazy?

8 normal people went to 12 psychological hospitals. They said they heard voices. Besdies that, they acted normally. All the subjects were admitted to all 12 hospitals. All but one was labeled schizophrenic.

Rosenhan’s point was that diagnosis has as much to do with the environment of diagnosed as it does with their symptoms. After Rosenhan, diagnosis couldn’t be done in psychological hospitals. Now, people don’t label as quickly.Rosenhan (1973). On being sane in insane places. Science, 179, 250-258.

Getting Defensive

Many of Freud’s ideas have been abandoned. One exception is his idea of defense mechanisms. His daughter, Anne, summarized these theories in The Ego and Mechanisms of Defense.

A defense mechanism is something our mind does to protect against anxiety. Anne named a few. With regression, one retreats into younger behavior. In projection, one projects one’s impulses onto other people. In reaction formation, one does the opposite of one’s “bad” impulses). There are others.Freud (1946). The ego and mechanisms of defense. New York: International Universities Press.

Helpless

By shocking dogs, Seligman found that helplessness could be both learned and unlearned. If you can’t control your outcomes many times in a row, you might think you have no control in later situations, even when you do have control.Seligman & Maier (1967). Failure to escape traumatic shock. Journal of Experimental Psychology, 74, 1-9.

Crowding

Calhoun studied the effects of crowding on lab rats. He found that crowding causes aggression in some, submissiveness in others, sexual deviance, and reproductive abnormalities. Later studies examined the relation between humans and crowding.Calhoun (1962). Population density and social pathology. Scientific American, 206(3), 139-148.

Psychotherapy

How to Choose a Therapist

Researchers summarized thousands therapy outcomes and found two things. (a) Therapy is better than no therapy. (b) The type of therapy given doesn’t matter much.

What really matters? (a) Your expectations for therapy, and (b) whether or not your therapist is genuine, caring, and empathic.Smith & Glass (1977). Meta-analysis of psychotherapy outcome studies. American Psychologist, 32, 752-760.

Relax

Wolpe developed “systematic desensitization” for beating phobias. A therapist can show you a scary stimulous (a photo of a spider) with a pleasant stimulous (candy). Done many times, this can defeat a phobia.Wolpe (1961). The systematic desensitization treatment of neuroses. Journal of Nervous and Mental Diseases, 132, 180-203.

The Inkblot Test

Rorschach showed subjects abstract shapes and asked them what the shapes were. Different types of people (depressed, schizophrenics, etc.) gave different types of responses.Rorschach (1942). Psychodiagnostics: A diagnostic test based on perception. New York: Grune & Stratton.

Interpreting People

Murray developed a new test. He showed drawings of people in ambiguous situations to his subjects. When it’s clear why the drawn people are doing what they’re doing, you probably interpret the drawing right. But if their reasons are ambiguous, your interpretation only says something about you.Murray (1938). Explorations in personality (pp. 531-545). New York: Oxford University Press.

Social psychology

Attitudes

LaPiere questioned whether one’s attitude really predicted one’s behavior. He took some Chinese people to restaurants across the USA. LaPiere measured the service they recieved. His results were complex but widely cited.LaPiere (1934). Attitudes and actions. Social Forces, 13, 230-237.

Conformity

Subjects were shown a standard line and several comparison lines. Then, researched asked them to choose the comparison line that was the same length as the standard line. It’s an easy test.

After many tests, all the other subjects choose the same wrong line. (They’re in cahoots with the researchers.) The volunteer must decide to go with the obviously correct choice or the one everyone else picked. 75% went along with the group!Asch (1955). Opinions and social pressure. Scientific American, 193(5), 31-35.

Help or Not?

In 1964, Kitty Genovese was attacked by a man with a knife. 38 people watched the attack for 35 minutes before someone called the police. By then, Kitty had died.

Because there were so many witnesses, most people thought “someone else will help, so I don’t need to.” With fewer witnesses, people are more likely to call the police.Darley & Latané (1968). Bystander intervention in emergencies: Diffusion of responsibility. Journal of Personality and Social Psychology, 8, 377-383.

Will You Obey?

Researchers asked volunteers to shock others with electricity when they answered a question wrong. The people being shocked were actors, pretending to be in pain.

65% of volunteers continued to obey the researcher and deliver shocks. Even when the actor screamed in pain and begged the volunteer to stop. We obey authorities even when we shouldn’t.Milgram (1963). Behavioral study of obedience. Journal of Abnormal and Social Psychology, 67, 371-378.

The future

Psychology is still a young science. Who knows what is right around the corner?