INTRODUCTION TO EXPERIMENTAL PSYCHOLOGY

Psychology 220

Chapter 1: Basics of Scientific Psychology Goals of Psychological Research

Make you think like a scientist about behavior Better understand how to conduct research

This allows use to test hypotheses This allows us to solve practical problems

Better understand how to evaluate research This involves learning how apply critical thinking to

research As a critic, you learn how to make an informed

judgment about the value of something This critique can result in either support or criticism of

a theory or hypothesis

Chapter 1 continued:

We make informed decisions in science using Experiments In an experiment, we test a hypothesis (a very specific

testable idea based upon a theory—which is a collection of ideas whose purpose is to describe, predict, or explain phenomena)

In an experiment we manipulate the independent variable (IV) while holding other potential IVs constant (control variables, or CVs), and then we examine the effect of the IV(s) on the dependent variable (DV)—the performance variable If the proper experimental design is not followed, then our

results can be confounded—e.g., fatigue or practice effects in a within-subjects design

Chapter 1 continued:

Example of a theory: Cognitive aging is primarily a function of the brain slowing down as a function of task complexity This is the “general slowing” theory of cognitive aging (e.g.,

Cerella, 1985; Salthouse, 1996) An example of a hypothesis is that age differences will be

proportional to task complexity We can test this hypothesis using an experiment in which we

vary word frequency (high vs. low), case type (lowercase vs. mixed-case), and response type (two-choice vs. go/no-go) on a lexical decision task (does a letter string form a real word, or not?) testing younger and older adults What are the IVs, CVs, and DVs?

After collecting our data, we test whether age differences in word frequency and case type are consistent with processing speed. It turns out that there are no appreciable age differences in word

frequency, but there are large differences in case type and response type, even though older adults are much slower—these results are inconsistent with general slowing (see Allen et al., 1993)

Chapter 1: Continued

This type of experiment is designed to isolate age effects at one, or multiple, information processing stages

We cannot directly observe thinking, so we indirectly infer it based upon the relation between stimulus conditions and subject behavior

This allows us to peer inside the “black box” of the human mind The mind is like trying to see what is present outside after

dark when you are sitting in a lighted room This is systems engineering of the mind

Chapter 1: Continued

In our design, we are manipulating case type (encoding), word frequency (lexical access), and response type (response selection)

We assume that humans go through sequential, functionally discrete processing stages i.e., the tend to finish a stage before they begin

another stage Using this approach, we can determine whether

age differences are isolated at a given stage or whether they are generalized across stages

Chapter 1 continued:

These results are important because they suggest that we do not simply “go down hill” as we age Indeed, in some situations, older adults

actually perform better than younger adults (e.g., Allen et al., 2002; Lien et al., 2006)

So it appears that aging is a combination of neural degeneration (that hurts performance) and skill acquisition (that helps performance)

Chapter 1 continued:

Sources of Research Ideas—Where do research ideas come from? Coming up with interesting, testable research ideas is

probably the most difficult part of science (including psychology). Scientists must be creative, and they need to practice this skill

Observation is a good place to begin generating research ideas (this allows you to observe what the important pieces of the puzzle are, and how they fit together)

New scientific ideas need to extend the existing literature Conducting a literature search allows you to confirm that

your idea is novel so that you do not steal others’ ideas (plagiarism). Additionally, others’ work can give you good research ideas PsycINFO is an effective search engine (although Google

works well in many circumstances, as well)

Chapter 1 continued:

Typical Steps in Research: Develop an idea (this is very difficult and takes creativity as

well as a comprehensive knowledge of the field) Formulate a testable hypothesis (make a statement about a

presumed or theoretical relation between two or more variables) This implies that these variables are measureable It also specifies the relations among the variables

Reviewing the literature—this term we will examine Time-of-Day effects on cognition

Conduct pilot research (to see if everything works) Complete your data collection (with a large enough sample

size) Conduct statistical analyses (statistics is the language of

science) Interpret your results Write up your results in an article

Chapter 1 Continued:

Present Project: Age Differences in Naming Theory: Cognitive aging effects are a

combination of cognitive and sensory/motor loss and skill increases Hypothesis: Loss of visual acuity should make

mixed-case presentation stimuli particularly difficult for older adults (compared to younger adults), but phonological regularity effects should be relatively constant across age

Method: have two sets of participants (younger and older adults) tested on a naming task that varies word frequency, phonological regularity, and case type

Chapter 1 continued:

Research Pitfalls to avoid: Breaches of ethical practice (Chapter 12) (falsification, fabrication,

plagiarism) The “golden rule” is not to do anything to a research subject that you would

not do to yourself This is a VERY complicated issue and we will discuss it in detail (e.g., non-

human animal research, human research, research on impoverished individuals who participate just for the money)

Biased research Inadvertent research bias—e.g., if your political beliefs resulted in you

interpreting results in a manner that went way beyond the data E.g., NPR caller that thought John McCain was too old to run for office and was

showing signs of either MCI or dementia Morton, skull size, intelligence and race (and Gould’s clarification) Double-blind design (both the researcher and the participant are blind to the

treatment type) Avoiding anthropomorphizing with non-human animals

Unreliable communication The cold war Science is inherently empirical, and it is important to have all the available

data in order to make our best conclusion about what theories work best

Chapter 2: Explanation in Scientific Psychology

Making Sense of the World—our attempt to discover how and why things work the way they do Social Loafing—people working in a group

do not work as hard as the same people working by themselves Why does social loafing occur?

Chapter 2: continued:

On March 13, 1964, Kitty Genovese was attacked and stabbed by Winston Moseley Mr. Moseley left for 15-60 minutes, and then

returned to finish murdering Kitty Genovese There were approximately 38 witnesses to one

or both of the stabbings, and no one called the police or went out to help Kitty Genovese

This phenomena in which groups of people seem more unwilling to help people in need has been referred to as the “unresponsive bystander” effect

Chapter 2 continued:

The unresponsive bystander effect (or social loafing) has been explained by the concept of “diffusion of responsibility”—people working by themselves think that they are responsible for completing a task (or helping someone), whereas people working in a group diffuse the responsibility for work to the group as a whole (e.g., it is society’s responsibility) Mention Bib Latane’s “smoke study” in Ohio Stadium

While there is some evidence that diffusion of responsibility can be attenuated (or even eliminated) by observing individual behavior in when someone is working in a group, this is still a powerful effect that can have an impact on work productivity and helping behaviors for people in need This has implications for whether “team” approaches to work

really can work as well as an approach that emphasizes individual responsibility

Chapter 2 continued:

Sources of Understanding Fixation of Belief—how we decide what we believe: The American

philosopher Charles Sanders Peirce (1877) discussed four types of fixation of belief: Method of Authority—take someone else’s word on faith for deciding

what you believe (e.g., a priest’s or minister’s view) Method of Tenacity—when a person steadfastly refuses to alter

acquired beliefs in spite of evidence to the contrary (e.g., the earth is flat)

A Priori Method—When something is believed without prior study or examination (an extension of the Method of Authority, except now, it is not based on a particular authority, but on a general cultural outlook

Scientific Method—fixes belief on the basis of experience and evidence Science is repeatable and self-correcting (e.g., when results are not

replicated consistently, we likely had a “false positive”) Empirical observation and manipulation (with experimental control) means

that in science, fixation of belief is based at least in part on actual data By self-correcting, we mean that science offers methods for establishing the

superiority of one belief over another

Chapter 2 continued:

Nature of Scientific Explanation Sir Francis Bacon (1561-1626) is credited with developing

much of the conceptual basis of empiricism—the empirical and self-correcting aspects of science

All accepted approaches to science share the same basic elements—data (empirical observations collected under experimental control) and theory (organization of concepts that permit prediction and explanation of data) Induction is working from data to theory (reasoning from specific to

general), and deduction is working from theory to data (reasoning from general to specific)

It is important to note that induction is probabilistic and that deduction is completely deterministic

In a very real sense, there is no need for data in deduction (logic is used instead

Laws in science almost involve deductive logic, but even laws do not always hold—particularly in psychology!

Chapter 2 continued:

Nature of Scientific Explanation Continued: Falsifiability—because of the temporary, probabilistic nature of

science, Popper (1961) has argued that negative evidence is more important than positive evidence, and that one can disprove a theory but cannot prove it *This is the null hypothesis testing approach to science, but your

professor heartily disagrees (people do not win Nobel Prizes for disproving a theory—it is usually for providing evidence in favor of a theory)

Direct hypothesis testing (why you did not remember some of what you learned in Statistics)

This is why we need to have better quantitative skills is psychology Theory->Deduction->Data->Induction->Theory Strong Inference—eliminating possible alternative explanations

by pitting two (or more) possible explanations (theories) against each other in a series of experiments in which each theory makes different predictions We will discuss converging operations later on

Chapter 2 continued:

Nature of Scientific Explanation Continued: From Theory to Hypothesis—theories typically

cannot be tested directly because they are too broad Instead theories generate very specific testable

statements (hypotheses) that can be evaluated based upon observable data from an experiment

Generalization—a broader statement (than a hypothesis) that cannot be tested directly but tends to come in between a theory (even more general) and hypotheses (more specific)

E.g., Older adults slow down compared to younger adults (theory), older adults are unsafe drivers at any speed (generalization), drivers older than 65 have a higher incidence of left-turn accidents across oncoming traffic than do younger adults (hypothesis)

Chapter 2 continued:

Nature of Scientific Explanation Continued: What is a theory?—it is a set of related statements that

explains a variety of occurrences. The more the occurrences and the fewer the statements, the better the theory (at least, in terms of parsimony) A theory in psychology performs at least three functions:

organization (a framework for the systematic and orderly display of data), prediction (it allows the scientist to generate predictions for situations in which no data have been obtained), and explanation (it allows the scientist to interpret results)

Explanation cannot occur directly from prediction—it can occur only on the basis of an experiment (sometimes several)

Inferring causality requires not only relating two or more variables, but also maintaining experimental control to rule out alternative causes

Chapter 2 continued:

Nature of Scientific Explanation Continued: Intervening variables—these link independent

variables (IVs) to dependent variables (DVs) even though we cannot directly observe them (e.g., perception and attention occur between a stimulus and a response—we can directly observe the latter two, but not the former two, although the intervening variables are required for a complete explanation Cognitive Psychology is based largely on unobservable

intervening variables—”systems engineering of the mind” (see Garner, Hake, and Erickson, 1956)

Chapter 2 continued:

Evaluating theories: Parsimony—the simplest theory is the best

(Occam’s razor) Precision—theories based upon math equations

or computer programs have many advantages because they are more precise than verbal statements Precision has advantages over parsimony in mature

sciences because it allows you to account for more results

Testability—even some precise theories cannot be tested, and this means they are not scientific theories Testability is the hallmark of science

Chapter 2 continued:

The Science of Psychology: hard and soft science Applied versus basic research The importance of realism

You must have internal validity to do science (ecological validity is not required, but external validity is)

Chapter 3: Exploring the Literature in Psychology How to do a literature search:

Psychological Abstracts—contains brief abstracts of articles (150 words or less) pertinent to psychology

PsycINFO—an electronic reference service that covers more than 1300 journals in psychology and related fields (e.g., neuroscience)

Google—is a useful search engine for your beginning search on a topic

Social Sciences Citation Index—can be used to search for articles or to determine how many times and an article has been cited (this is used to evaluate scholarship—e.g., for promotion processes)

Academic Search Complete (EBSCO)—a very broad electronic reference service for all of science (4,400 peer-reviewed journals) Use Advanced Search, though

Chapter 3 continued:

Parts of an article: Title: Provides an idea of what the article is about Authors: knowing the authors’ past theoretical

orientation can frequently provide you with an idea of the approach that will be taken in this article

Abstract: “A brief comprehensive summary of the contents of an article …” (p. 12, Publication manual of the APA).

Introduction: Specifies the problem to be studied, some shortcomings in the present level of understanding, and how this study will attempt to overcome some of these shortcomings It also specifies the hypotheses to be tested and the

rationale behind these predictions This is typically the most difficult portion of the paper to

write

Chapter 3 continued:

Parts of an article continued: Method—describes in detail the operations to be performed in the

study. This section is usually printed in smaller type than the rest of the article, but not always (e.g., JML) Contains subject, apparatus, materials, and procedures sections

Results—describes the outcome of your experiment(s) and reports the statistical analyses of your data Figures are easier to interpret, but they are not as precise for archival data

purposes Discussion—this is the portion of the article in which the author

restates the results in a manner that allows readers to understand how the present results impacted upon theory, and the theoretical implications of the study Frequently the Intro goes from general to specific, but the Discussion goes

from specific (your results in this study) to general (what implications these results have for broader theoretical issues)

References—this is the section in which references are listed alphabetically, the first line is not indented, but subsequent lines are This is a time-consuming part of writing a paper, but references are used as

proof for your contentions It is typically good to average at least two references per page of text

Chapter 4: Observational Research in Psychology: Descriptive Observations—examine what

behaviors occur and in what frequency Four Types of Descriptive observations:

Naturalistic observations: description of naturally occurring events without intervention on the part of the investigator Ethology—the study of naturally occurring behavior (typically

in the “wild”), is the most common type of naturalistic observation

Simply observing behavior is a good way to generate new research ideas, but more systematic methods are typically needed in order to explain naturally occurring phenomena

E.g., how does a honey bee’s “waggle dance” specifiy the location and distance of a food source?

Chapter 4 continued:

Ethologists observe systematically by identifying different categories of experience for the organism under study by recording the number of times the organism engages in each behavior, the intensity of the interaction, and the outcome These behaviors might be sub-divided into mating, grooming,

fighting, eating, and social hierarchies These behaviors are recorded in an ethogram—a relatively complete

inventory of specific behaviors performed by one species of animal Timberlake and Silva (1994) have argued that ethograms should be

designed to answer certain research questions rather than to describe and classify behavior completely

However, you cannot answer research questions using just observation—because you do not have the experimental control to rule out alternative explanations

E.g., the honey bee might fly in a certain direction because of the wind rather than to show other bees where food is—or, perhaps, the bee is performing a “location” dance, but is warning other bees of danger rather than the location of food

Chapter 4 continued:

Ethology continued: Inter-observer reliability—this method is used

to increase the reliability of observations—it is when the observations of two or more observers yield similar results when they simultaneously observe the same behavior (using a correlation coefficient)

When anthropologists are studying people, though, it is difficult to remain unbiased Frequently ethologists do not passively observe—

instead they actively observe (e.g., by becoming part of a tribe or a gorilla hierarchy)

In both passive and active approaches, it is difficult to prevent bias from affecting results

Chapter 4 continued:

Ethology: Examples: Tinbergen’s stickleback fish and sign

stimuli and the resulting fixed action patterns http://en.wikipedia.org/wiki/

Fixed_action_pattern Lorenz’ geese and imprinting

Chapter 4 continued:

The Case Study: an intense investigation of a particular instance of some behavior (the “method clinique” of Piaget) While this approach is certain descriptive and may provide ideas for

more careful research (with better experimental control), it does NOT allow inferences of case-and-effect E.g., child show different levels of conservation skills depending on the

familiarity of the context (if they are tested at home, they perform better than if they are tested in an unfamiliar setting)

Deciding how cognitive development works based upon observing one’s own children is complicated because of observer bias (e.g., Piaget thought that most children would develop formal operations, but up to 50% of adults apparently do not)

Deviant-case analysis—attempts to minimize the difficulties of making inferences by comparing two similar cases that differ in specific ways

The goal is to pinpoint, through careful comparison of two cases, the factors that are responsible for the different outcome

But you still have no experimental control to equate the two cases except for one IV

H.M. and his loss of the ability to form new long-term episodic memories But it is probably difficult to generalize from H.M. to “normal” humans because of his

brain damage In other words, we do not know if everything thing else is the same in H.M.

except for his lesion (we have no experimental control)

Chapter 4 continued:

Survey Research—the techniques of obtaining a limited amount of information from a large number of people, usually through random or stratified sampling Proctor and Gamble example of detergent

preferences See response styles below, though, for

limitations Political poles show how hard it is to get

respondents to reply truthfully

Chapter 4 continued:

Meta-Analysis—a relatively objective statistical method for summarizing across the results of many studies investigating a single topic Meta-analysis can help determine the external

validity and relative strength of a given phenomenon Psychological Bulletin is a psychology journal that

emphasizes meta-analyses Verhaeghen’s work on vocabulary performance and

aging

Chapter 4 continued: Advantage of descriptive methods—this approach is useful in the early

stages of research to help generate research hypotheses However, it lacks the required experimental control to infer causality Also, while naturalistic observation emphasizes ecological validity (realism), this

does not mean that it has either internal validity or external validity Sources of Error in Descriptive Methods:

It does not allow one to assess relations among events (determining antecedent conditions cannot be done because there was no manipulation to determine this)

Researcher bias is a problem because of the tendency to try to interpret the results rather than to describe them

Anthropomorphizing—attributing human characteristics to non-human animals that the non-human animals do not possess

Reactivity—when observations are influenced by (or are a reaction to) the detected presence of the investigator This results in subject roles (a demand characteristic) that puts pressure on subjects to

respond in a certain way In naturalistic observation, unobtrusive observation can be difficult to obtain

Participant observation (when the observer become “one of the gang) causes at least as many problems as an attempted solution

Case Studies—are retrospective and thus typically involve both unmotivated (memory failure) and motivated (repression) forgetting

Chapter 4 continued:

Sources of Error in Descriptive Methods continued: Surveys, interviews, and tests can be

biased by response styles: Response acquiescence Response deviation Social desirability Volunteer problem

Chapter 5: Relational Research Relational Research—how two or more variables

are related to each other Usually relational (or correlational) research does not

involve the manipulation of variables (as is done in experiments), so data are related ex post facto (or after-the-fact)

The relationship occurs because of naturally occurring evens and not necessarily because one variable causes another Without experimental control, you do not know whether

some other variable is mediating the relationship between the two variables that you are observing

E.g., our noted relationship between ice cream consumption and the probability of murdering someone

The third unobserved variable—temperature—is likely mediating the relationship between ice cream consumption and the probability of murder

Chapter 5 continued:

Types of relational research: Contingency Table Research (chi-square test of

independence)—is used when both of your variables are categorical (e.g., the relation between major type and gender type) This method employs a tabular presentation of all

combinations of categories of two variables (which allows the relationships between the two variables to be examined)

A chi-square test of independence is used to determine whether these two variables are independent, or not

The null hypothesis is that major type and gender type are not related (independent)

The alternative hypothesis is that major type and gender type are related (dependent)

You do not know whether one variable caused the other, you just know if they are related

Chapter 5 continued:

Types of Relational Research continued: Correlational research methods and analysis are used

when your two variables are continuous (quantitative variables)—but you still do not have experimental control This method allows one to determine both the degree

(magnitude) and direction of the relationship between two variables

Correlation coefficient—a measure of the degree and direction of the relationship between two variables

It can vary from -1.00 to 0 (no relationship) to 1.00. The magnitude of the correlation coefficient indicates the

degree of the relationship between the two variables (e.g., .80 is stronger than .60)

The sign of the correlation (positive or negative) indicates the direction of the relationship (for positive, as x increases, y increases; for negative, as x increases, y decreases)

Chapter 5 continued:

Correlations continued: Examine the scatter diagram of plotted data points in x-

and y-space to make sure that there is a linear relationship (because you are using the general linear model in least-squares estimation) If you have a linear scatter plot, then you can see whether

you have a positive correlation (positive slope) or a negative correlation (negative slope

Correlation does not imply causation—it simply implies the existence of a relationship

Low correlations can occur because there is no effect, because you have a non-linear scatter plot, because you have a truncated range, or because you do not have enough statistical power to detect the effect (i.e., you need a larger sample size examples

Chapter 5 continued:

Correlations continued: Complex correlation procedures: cross-

lagged-panel correlations See example on TV watching and aggressive

behavior In spite of this, though, we still do not know if some

uncontrolled third variable caused the relationship

Chapter 5 continued:

Inferences of Causation require that internal validity holds (i.e., that you IV really does cause the change on the DV)

The real utility of correlational methods is their ability to predict, not to explain

In determining causation, things can get quite complicated because we can have many proximate causes (immediate cause of death such as a heart attack) but a hopefully a single ultimate cause (atherosclerosis) Therefore, we frequently are careful in not over-stating causes

(because we are not sure that we have the ultimate cause isolated in our experiment—it could just be a proximate cause) E.g., time is the not the ultimate cause of aging decrements—

processing that occur over time are, but time is such a handy variable that we still use it as a label for developmental causes