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The idea that psychology is based on empirical evidence means that

Is Psychology a Science?

By Dr. Saul McLeod, updated 2020

Science uses an empirical approach. Empiricism (founded by John Locke) states that the only source of knowledge comes through our senses – e.g. sight, hearing etc.

This was in contrast to the existing view that knowledge could be gained solely through the powers of reason and logical argument (known as rationalism).  Thus, empiricism is the view that all knowledge is based on, or may come from experience.

The empirical approach through gaining knowledge through experience quickly became the scientific approach and greatly influenced the development of physics and chemistry in the 17th and 18th centuries.

empiricism psychology science

The idea that knowledge should be gained through experience, i.e. empirically, turned into a method of inquiry that used careful observation and experiments to gather facts and evidence.

The nature of scientific inquiry may be thought of at two levels:

1. that to do with theory and the foundation of hypotheses.

2. and actual empirical methods of inquiry (i.e. experiments, observations)

The prime empirical method of inquiry in science is the experiment.

The key features of the experiment are control over variables (independent, dependent and extraneous), careful objective measurement and establishing cause and effect relationships.

The Key Features of a Science

Empirical Evidence

o Refers to data being collected through direct observation or experiment.

o Empirical evidence does not rely on argument or belief.

o Instead, experiments and observations are carried out carefully and reported in detail so that other investigators can repeat and attempt to verify the work.


o Researchers should remain totally value free when studying; they should try to remain totally unbiased in their investigations. I.e. Researchers are not influenced by personal feelings and experiences.

o Objectivity means that all sources of bias are minimized and that personal or subjective ideas are eliminated. The pursuit of science implies that the facts will speak for themselves, even if they turn out to be different from what the investigator hoped.


o All extraneous variables need to be controlled in order to be able to establish cause (IV) and effect (DV).

Hypothesis testing

o E.g. a statement made at the beginning of an investigation that serves as a prediction and is derived from a theory. There are different types of hypotheses (null and alternative), which need to be stated in a form that can be tested (i.e. operationalized and unambiguous).


o This refers to whether a particular method and finding can be repeated with different/same people and/or on different occasions, to see if the results are similar.

o If a dramatic discovery is reported, but it cannot be replicated by other scientists it will not be accepted.

o If we get the same results over and over again under the same conditions, we can be sure of their accuracy beyond reasonable doubt.

o This gives us confidence that the results are reliable and can be used to build up a body of knowledge or a theory: vital in establishing a scientific theory.


o We should be aiming to be able to predict future behavior from the findings of our research.

The Scientific Process

Before the twentieth century, science largely used the principles of induction – making discoveries about the world through accurate observations, and formulating theories based on the regularities observed.

Newton’s Laws are an example of this.  He observed the behavior of physical objects (e.g. apples) and produced laws that made sense of what he observed.

The scientific process is now based on the hypothetico-deductive model was proposed by Karl Popper (1935).  Popper suggested that theories/laws about the world should come first and these should be used to generate expectations/hypotheses which can be falsified by observations and experiment.

Falsification is the only way to be certain – as Popper pointed out: ‘No amount of observations of white swans can allow the conclusion that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion’

Darwin’s theory of evolution is an example of this. He formulated a theory and set out to test its propositions by observing animals in nature.  He specifically sought to collect data to prove his theory / disprove.

Thomas Kuhn argued that science does not evolve gradually towards truth, science has a paradigm which remains constant before going through a paradigm shift when current theories can’t explain some phenomenon, and someone proposes a new theory. Science tends to go through these shifts therefore psychology is not a science as it has no agreed paradigm. There are many conflicting approaches and the subject matter of Psychology is so diverse therefore researchers in different fields have little in common.

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Psychology is really a very new science, with most advances happening over the past 150 years or so.  However, it can be traced back to ancient Greece, 400 – 500 years BC.  The emphasis was a philosophical one, with great thinkers such as Socrates influencing Plato, who in turn influenced Aristotle. 

Plato argued that there was a clear distinction between body and soul, believed very strongly in the influence of individual difference on behavior, and played a key role in developing the notion of “mental health”, believing that the mind needed stimulating by the arts to keep it alive. Aristotle firmly believed in the idea that the body strongly affected the mind – you might say he was an early bio psychologist.

Psychology as a science took a “back seat” until Descartes (1596 – 1650) wrote in the 17th century. He believed strongly in the concept of consciousness, maintaining that it was that that separated us from animals.

He did, however, believe that our bodies could influence our consciousness and that the beginnings of these interactions were in the pineal gland – we know now that this is probably NOT the case!

From this influential work came other important philosophies about psychology, including work by Spinoza (1632 – 1677) and Leibnitz (1646 – 1716). But there still was no single, scientific, unified psychology as a separate discipline (you could certainly argue that there still isn’t!).

When asked the question “Who is the parent of psychology?”, many people answer “Freud”. Whether this is the case or not is open to debate, but if we were to ask who the parent of experimental psychology is, few would be likely to respond in the same way.  So where did modern experimental psychology come from and why?

Psychology took so long to emerge as a scientific discipline because it needed time to consolidate.  Understanding behavior, thoughts and feelings is not easy, which may explain why it was largely ignored between ancient Greek times and the 16th century.

But tired of years of speculation, theory and argument, and bearing in mind Aristotle’s plea for scientific investigation to support theory, psychology as a scientific discipline began to emerge in the late 1800’s.

Wilheim Wundt developed the first psychology lab in 1879.  Introspection was used, but systematically (i.e. methodologically). It was really a place from which to start thinking about how to employ scientific methods to investigate behavior.

The classic movement in psychology to adopt these strategies were the behaviorists, who were renowned for their reliance on controlled laboratory experiment and rejection of any unseen or subconscious forces as causes of behavior.  And later, the cognitive psychologists adopted this rigorous (i.e. careful), scientific, lab based approach too.

Psychological Approaches and Science

Psychoanalysis has great explanatory power and understanding of behavior, but is has been accused of only explaining behavior after the event, not predicting what will happen in advance and of being unfalsifiable.

Some have argued that psychoanalysis has approached the status more of a religion than a science, but it is not alone in being accused of unfalsifiable (evolutionary theory has too – why is anything the way it is?

Because it has evolved that way!) and like theories that are difficult to refute – the possibility exists that it is actually right.

Kline (1984) argues that psychoanalytic theory can be broken down into testable hypotheses and tested scientifically. For example, Scodel (1957) postulated that orally dependent men would prefer larger breasts (a positive correlation), but in fact found the opposite (a negative correlation).

Although Freudian theory could be used to explain this finding (through reaction formation – the subject showing exactly the opposite of their unconscious impulses!), Kline has nevertheless pointed out that theory would have been refuted by no significant correlation.

Behaviorism has parsimonious (i.e. economical / cost cutting) theories of learning, using a few simple principles (reinforcement, behavior shaping, generalization, etc.) to explain a vast variety of behavior from language acquisition to moral development.

It advanced bold, precise and refutable hypotheses (such as Thorndike’s law of effect) and possessed a hard core of central assumptions such as determinism from the environment (it was only when this assumption faced overwhelming criticism by the cognitive and ethological theorists that the behaviorist paradigm / model was overthrown).

Behaviorists firmly believed in the scientific principles of determinism and orderliness, and thus came up with fairly consistent predictions about when an animal was likely to respond (although they admitted that perfect prediction for any individual was impossible).

The behaviorists used their predictions to control the behavior of both animals (pigeons trained to detect life jackets) and humans (behavioral therapies) and indeed Skinner, in his book Walden Two (1948), described a society controlled according to behaviorist principles.

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Cognitive psychology – adopts a scientific approach to unobservable mental processes by advancing precise models and conducting experiments upon behavior to confirm or refute them.

Full understanding, prediction and control in psychology is probably unobtainable due to the huge complexity of environmental, mental and biological influences upon even the simplest behavior (i.e. all extraneous variables cannot be controlled).

You will see therefore, that there is no easy answer to the question ‘is psychology a science?’. But many approaches of psychology do meet the accepted requirements of the scientific method, whilst others appear to be more doubtful in this respect.

Alternatives to the Scientific Approach

However, some psychologists’ argue that psychology should not be a science. There are alternatives to empiricism, such as rational research, argument and belief.

The humanistic approach (another alternative) values private, subjective conscious experience and argues for the rejection of science.

The humanistic approach argues that objective reality is less important than a person’s subjective perception and subjective understanding of the world. Because of this,Carl Rogers and Maslow placed little value on scientific psychology, especially the use of the scientific laboratory to investigate both human and other animal behavior.

A person’s subjective experience of the world is an important and influential factor on their behavior. Only by seeing the world from the individual’s point of view can we really understand why they act the way they do. This is what the humanistic approach aims to do.

Humanism is a psychological perspective that emphasizes the study of the whole person. Humanistic psychologists look at human behavior not only through the eyes of the observer, but through the eyes of the person doing the behaving. Humanistic psychologists believe that an individual’s behavior is connected to his inner feelings and self-image.

The humanistic approach in psychology deliberately steps away from a scientific viewpoint, rejecting determinism in favor of freewill, aiming to arrive at a unique and in depth understanding. The humanistic approach does not have an orderly set of theories (although it does have some core assumptions) and is not interested in prediction and controlling people’s behavior – the individuals themselves are the only ones who can and should do that.

Miller (1969) in “Psychology as a Means of Promoting Human Welfare” criticizes the controlling view of psychology, suggesting that understanding should be the main goal of the subject as a science, since he asks who will do the controlling and whose interests will be served by it?

Humanistic psychologists rejected a rigorous scientific approach to psychology because they saw it as dehumanizing and unable to capture the richness of conscious experience.

In many ways the rejection of scientific psychology in the 1950s, 1960s and 1970s was a backlash to the dominance of the behaviorist approach in North American psychology.

Common Sense Views of Behavior

In certain ways everyone is a psychologist. This does not mean that everyone has been formally trained to study and be trained in psychology.  People have common sense views of the world, of other people and themselves. These common sense views may come from personal experience, from our upbringing as a child and through culture etc.

People have common-sense views about the causes of their own and other people’s behavior, and personality characteristics they and others posses, about what other people should do, how to bring up your children, and many, many more aspects of psychology.

The informal psychologists’ acquires common-sense knowledge in a rather subjective (i.e. unreliable) and anecdotal way.  Common-sense views about people are rarely based on systematic (i.e. logical) evidence, and are sometimes based on a single experience or observation.

Racial or religious prejudices may reflect what seems like common sense within a group of people. However, prejudicial beliefs rarely stand up to what is actually the case.

Common sense, then, is something which everybody uses in their day-to-day lives, guides decisions and influences how we interact with one another.

But because it is not based on systematic evidence, or derived from scientific inquiry, it may be misleading and lead to one group of people treating others unfairly and in a discriminatory way.

Limitations of Scientific Psychology

Despite having a scientific methodology worked out (we think), there are further problems and arguments which throw doubt onto psychology ever really being a science. 

Limitations may refer to the subject matter (e.g. overt behavior versus subjective, private experience), objectivity, generality, testability, ecological validity, ethical issues and philosophical debates etc.

Science assumes that there are laws of human behavior that apply to each person. Therefore science takes both a deterministic and reductionist approach.

Science studies overt behavior because overt behavior is objectively observable and can be measured, allowing different psychologists to record behavior and agree on what has been observed. This means that evidence can be collected to test a theory about people.

Scientific laws are generalizable, but psychological explanations are often restricted to specific times and places. Because psychology studies (mostly) people, it studies (indirectly) the effects of social and cultural changes on behavior.

Psychology does not go on in a social vacuum. behavior changes over time, and over different situations. These factors, and individual differences, make research findings reliable for a limited time only.

Are traditional scientific methods appropriate for studying human behavior? When psychologists operationalize their IV, it is highly likely that this is reductionist, mechanistic, subjective, or just wrong.

Operationalizing variables refer to how you will define and measure a specific variable as it is used in your study. For example, a bio psychologist may operationalize stress as an increase in heart rate, but it may be that in doing this we are removed from the human experience of what we are studying. The same goes for causality.

Experiments are keen to establish that X causes Y, but taking this deterministic view means that we ignore extraneous variables, and the fact that at a different time, in a different place, we probably would not be influenced by X. There are so many variables that influence human behavior that it is impossible to control them effectively. The issue of ecological validity ties in really nicely here.

Objectivity is impossible. It is a huge problem in psychology, as it involves humans studying humans, and it is very difficult to study the behavior of people in an unbiased fashion.

Moreover, in terms of a general philosophy of science, we find it hard to be objective because we are influenced by a theoretical standpoint (Freud is a good example of this). The observer and the observed are members of the same species are this creates problems of reflectivity.

A behaviorist would never examine a phobia and think in terms of unconscious conflict as a cause, just like Freud would never explain it as a behavior acquired through operant conditioning.

This particular viewpoint that a scientist has is called a paradigm (Kuhn, 1970). Kuhn argues that most scientific disciplines have one predominant paradigm that the vast majority of scientists subscribe to.

Anything with several paradigms (e.g. models – theories) is a pre-science until it becomes more unified. With a myriad of paradigms within psychology, it is not the case that we have any universal laws of human behavior, and Kuhn would most definitely argue that psychology is not a science.

Verification (i.e. proof) may be impossible. We can never really, truly prove a hypothesis, we may find results to support it until the end of time, but we will never be 100% confident that it is really true.

It could be disproved at any moment. The main driving force behind this particular grumble is Karl Popper, the famous philosopher of science and advocator of falsificationism.

Take the famous Popperian example hypothesis: “All swans are white”. How do we know for sure that we will not see a black, green or hot pink swan in the future? So even if there has never been a sighting of a non-white swan, we still haven’t really proven our hypothesis.

Popper argues that the best hypotheses are those which we can falsify – disprove. If we know something is not true, then we know something for sure.

Testability: much of the subject matter in psychology is unobservable (e.g. memory) and therefore cannot be accurately measured. The fact that there are so many variables that influence human behavior that it is impossible to control the variables effectively.

So, are we any closer to understanding a) what science is, and b) if psychology is a science? Unlikely. There is no definitive philosophy of science, and no flawless scientific methodology.

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When people use the term “Scientific” we all have a general schema of what they mean, but when we break it down in the way that we just have done, the picture is less certain. What is science? It depends on your philosophy. Is psychology a science? It depends on your definition. So – why bother, and how do we conclude all this?

Slife and Williams (1995) have tried to answer these two questions:

    1) We need to try at least to strive for scientific methods because we need a rigorous discipline. If we abandon our search for unified methods, we’ll lose a sense of what psychology is (if we knew in the first place).

    2) We need to keep trying to develop scientific methods that are suitable to studying human behavior – it may be that the methods adopted by the natural sciences are not appropriate for us.

How to reference this article:

McLeod, S. A. (2008). Psychology as a science. Simply Psychology.



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