Invitation to Psychology

18 Chapter 1 What Is Psychology?

Suppose you wanted to learn about drug use

among first-year college students. Questioning or

observing every first-year student in the country

would obviously not be practical; instead, you

would need to recruit a sample. You could use

special selection procedures to ensure that this

sample contained the same proportion of women,

men, blacks, whites, Asians, Latinos, poor people,

rich people, Catholics, Jews, Muslims, atheists,

and so on as in the general population of new

college students. Even then, a sample drawn just

from your own school or town might not produce

results applicable to the entire country or even

your state.

A sample’s size is less critical than its repre-

sentativeness. A small but representative sample

may yield extremely accurate results, whereas a

study that fails to use proper sampling methods

may yield questionable results, no matter how

large the sample. But in practice, psycholo-

gists must often settle for a sample of people

who happen to be available—a “convenience”

sample—and usually this means undergraduate

students. Most of the time, that’s fine; many

psychological processes, such as basic percep-

tual or memory processes, are likely to be the

same in students as in anyone else. But college

students, on average, are also younger and tend

to have better cognitive skills than nonstudents.

Moreover, most research participants, whether

You are about to learn...

•    how participants are selected for psychological

studies, and why it matters.

•    the methods psychologists use to describe

behavior.

•    the advantages and disadvantages of each

descriptive method.

Descriptive Studies:

establishing the Facts

Psychologists gather evidence to support their

hypotheses by using different methods, depend-

ing on the kinds of questions they want to answer.

These methods are not mutually exclusive, how-

ever. Just as a police detective may rely on DNA

samples, fingerprints, and interviews of suspects

to figure out “who done it,” psychological sleuths

often draw on different techniques at different

stages of an investigation.

No matter what technique is used, one of the

first challenges facing any researcher is to select

the participants (sometimes called “subjects”) for

the study. Ideally, the researcher would prefer to get

a representative sample, a group of randomly chosen

participants that accurately represents the larger

population that the researcher is interested in.

representative sample
A group of individuals,
selected from a popula-
tion for study, which
matches that population
on important characteris-
tics such as age and sex.

Recite & Review

Recite: Out loud, say as much as you can about theories, hypotheses, operational definitions, the

principle of falsifiability, the confirmation bias, and the importance of replication.

Review: Next, go back and reread this section to see what you might have left out.

Now bulk up your thinking muscles by answering these Quick Quiz questions:

1. Benjamin Rush, an eighteenth-century physician, believed that yellow fever should be treated
   by blood-letting. Many of his patients died, but Rush did not lose faith in his approach; he at-
   tributed each recovery to his treatment and each death to the severity of the disease (Stanov-
   ich, 2010). How did his explanations violate critical thinking?


2. Amelia and Harold are arguing about the death penalty. “Look, I just feel strongly that it’s
   barbaric, ineffective, and wrong,” says Harold. “You’re nuts,” says Amelia, “I believe in an eye
   for an eye, and besides, I’m absolutely sure it’s a deterrent to further crime.” Which lapses of
   critical thinking might Amelia and Harold be committing?
   Answers:

Study and Review at mypsychlab

Rush failed to analyze and test his assumptions; he violated the principle of falsifiability, explaining away each death, 1.

so there was no possible counterevidence that could refute the theory (which by the way was dead wrong; the treatment

Harold and Amelia are reasoning emotionally (“I feel strongly about this, 2. was actually as dangerous as the disease).

so I’m right and you’re wrong”). They do not cite evidence that supports or contradicts their arguments. What do studies

show about the link between the death penalty and crime? How often are innocent people executed? They have not

examined their biases. And they may not be clearly defining the problem: What is the purpose of the death penalty? Is

it to deter criminals, to satisfy the public desire for revenge, or to keep criminals from being paroled and returned to the

streets?