The Scientific Method in Psychology

Lecture

What is Psychology

• Commonly defined as the scientific study of mind, brain, and behaviour

• Cognitive, neuro, biological, developmental, social, organisation, evolutionary

What Defines a Science?

Features of a Science

• Science is grounded in observations

  • data is needed to confirm

• Science is cumulative

• Science is self-correcting

• Science achieves explanation and understanding

Falsification and the Logic of Scientific Discovery

• The scientific method implies incremental refinement

  • our knowledge progressively becomes a closer approximation to truth/reality

  • observation/data → explanation/theory → prediction/hypothesis

Critical Thinking

• Real scientific inference requires exercising judgement

  • How trustworthy are the data upon which influences are based? (Judgements about the quality of the data)

  • Is the theoretical explanation a general one, or is it limited to this specific instance? (Judgements about the adequacy of theory)

  • Does the experiment show the effect that the researcher thinks it does or if the effect arises for the reasons the experimenter thinks it does? (Judgements about the alternative explanations)

Judgments About Data

• Is the evidence reliable?

  • Is the measures a valid indicator of the construct?

  • Does repeating the experiment achieve the same results

Reliability and Validity

• Ideally, measures should be both reliable and valid

  • both are required for making legitimate inferences

• Reliability refers to how “repeatable” or consistent a measure is

  • if you were to asses the same construct in the same way, using the same method of measurement, do you tend to get the same results?

• Validity refers to the degree to which a measure assesses the thing it is purposed to assess

  • Is the construct you seek to measure actually related to the measurement?

Cranial Capacity and Intelligence?

• Racial Hierarchy = general consensus was that whites were on top and blacks on the bottom—but this had no supporting data

• Morton came up with measuring cranical capacity to find out the intelligence

• Bigger skull→bigger brain=more intelligent

Reliable but Not Valid

• Problem = cranial capacity does not really relate to intelligence, but it does relate to overall body size

  • Morton’s measure conflated with body size

• If the measure is not a valid reflection of the construct of interest, neither are the inferences based on the measure

Judgements about Theory

• Is the theory general?

  • A scientific explanation should apply to more than just one specific case

• Can the theory be tested?

  • Does the theory predict novel observations?

  • Are there results that would falsify the theory?

• Is the theory parsimonious?

  • A parsimonious theory provides the simplest possible explanation that suffices to explain all relevant observations

  • Principle of Ockham’s Razor

• Can we rule out alternative explanations?

  • If multiple explanations can explain the data is there a way to distinguish them?

Judgments About Alternative Explanations

• Correlation vs Causation

  • Because two variables are related to each other does not mean that one causes the other

Measurement & Uncertainty

Uncertainty and Quantitative Measurement

• Allows us to put a numerical value on a measurement

  • Quantifies our uncertainty

  • Permits objective measurement by others

• Most importantly, Quantitative Measurement allows for comparisons

  • Of groups of individuals

  • Of the same individual through time

Samples and Populations

• In most cases, we measure something about a sample of people and seek to form generalised conclusions in the population at large

  • What is true of the sample/population need not be true of the individual

  • What is true of the sample need not be trust of another sample (even if both are drawn from the same population)

  • For example, a study using the big five personality test with 2000 women and 2000 men found that women scored much higher than men in their agreeableness. From these samples it was inferred that women are generally more agreeable than men. This does not mean that all 2000 women were more agreeable than all 2000 men, or that a repeated study of 4000 different people from the same city would demonstrate the same results. However, there were clearly individual women that were more agreeable (according to the test) than individual men in order to get this result. Furthermore, what is true of the sample (women are more agreeable than men), is not true of all women in the area where the sample was taken. However there are obviously individual women who are more agreeable than individual men in the general population area.

Uncertainty and Replication

• Testing the efficacy of a treatment for depression

  • Can compare a control group (standard treatment) with a new treatment group.

  • Then, assess post-treatment depression score—is the new treatment effective? (Lower post-depression in new treatment to standard treatment)

Implications: Inference is Uncertain

• Sometimes a study will produce evidence for an effect when there is no true effect to be found

  • false positive rate (5%)

• Sometimes a study will fail to produce evidence for an effect even though there is a true effect to find

The Scientific Method

• Science is defined as any discipline that makes use of the so-called scientific method.

• This is an approach to understanding the world through cycles of developing and testing theories.

• Psychology is a scientific discipline through its reliance on the scientific method for refining our understanding of mind, brain, and behaviour.

• The scientific method is the iterative means by which scientific knowledge is amassed tested and refined.

• It describes the relationship between three components:

  • Observations/data

    • data are facts about the world; they are phenomena that a scientific discipline seeks to explain

  • Explanations or theories

    • theories are statements that seek to organise data coherently

    • the structure of theories tends to be shaped by data

    • a theory explains how different observations relate to one another and, more importantly, explains why the facts are the way that they are

  • Predictions or hypotheses

    • logical implications that follow from a theory

    • predictive statements that can be shown to be consistent or inconsistent with future observations

• Theories must have two properties to be considered scientific:

  • Testable predictions — does the theory generate hypotheses that can be evaluated against data?

  • Falsifiability — the predictions must allow for the theory to be shown to be false. That is, the theory must be able to make a prediction that can, in principle, be shown to be incorrect.

• Refining scientific knowledge

  • If a theoretical prediction is confirmed by the observation, then the theory is provisionally accepted, and another hypotheses is tested

  • A theory successfully predicting something does not confirm the theory. Rather, a theory that successfully predicts data is simply one that can be kept and tested again

  • If a theory generates predictions that are shown to be inconsistent with subsequent observations, then the theory can be considered to be falsified.

    • If it is falsified, the theory can then be adjusted by refining its assumptions and seeing if revisions of the theory can bring it in accord with the data, or, the theory can be rejected outright and abandoned in favour for some other alternative thory

Paradigms in Psychology

• Paradigm = a typical example or pattern of something; distinct set of concepts or thought patterns, including theories, research methods, postulates, and standards for what constitute legitimate contributions to a field; a framework for understanding and investigation phenomena within a discipline

• They determine what standard standard operation—or normal scientific activities—within a discipline looks like

• Paradigms define

  • concepts that are used in theories

  • research questions that are addressed by a discipline

  • methodologies used to investigate these questions

• Paradigms offer perspective on how phenomena are understood and the means by which once can achieve an understanding of phenomena

  • Similar concepts include ideologies (liberalism, etc) and world views (atheistic or theistic world view) as they will affect and change your opinions on matters

• There are five major paradigms in the history of psychology

  • clinical practice

    • psychodynamic

    • humanist

  • experimental psychology (adheres to scientific method)

    • behaviourist

    • cognitive

    • biological

Behaviourist Paradigms

• Arose partly due to the rejection of Freud’s psychodynamic theories

• Behaviourist psychologists encouraged people to consider how the external environment shapes our thoughts and behaviours

• Humans, and other animals, can be viewed as blank states whose psychology is determined wholly by the external environment

  • “product of one’s environment”

Methodological Behaviourism

• John B. Watson, early 1900s

• According to Watson, a proper scientific psychology must focus on publicly observable phenomena, such as overt behaviours

• Shifted study to relationships between publicly and observable stimuli and their behavioural consequences

Radical Behaviourism

• BF Skinner

• Skinner suggests that internal events, such as thoughts and feelings, could be understood according to the same learning principles that can explain publicly observable behaviours

• Although, the external environment was still viewed as the determinant of both observable and unobservable behaviours

• Rejects the idea that mind and mental events play any causal roles in human psychology—they are ultimately caused by external factors

Cognitive Paradigm

• Moved away from Behaviourism in the 1950s

• Places mental events at the centre of psychological research

• Regarded as the current dominant paradigm in psychology

• The key assertions that mental events can be studied scientifically and that they play a causal role in determining behaviour

• Seeks to understand the processes that “transform” stimuli into behaviours

• Most of the research conducted in this paradigm concern itself with identifying cognitive processes that are required to relate changes in stimuli with changes in behaviour

• Determining how unobservable processes interact is inherently a difficult task, and so a lot of contemporary work makes use of sophisticated mathematical models that attempt to quantitatively describe how different cognitive processes interact

Biological Paradigm

• Does not focus exclusively on abstract functional relationships between cognitive processes

• Seeks to explain cognition and behaviour in terms of biological processes

• Synergistic with work within cognitive and behaviourist paradigms

• fMRI and EEGs allow research to identify neural correlates of cognition and behaviour

• Research in the biological paradigm is often more interested in the biological mechanisms that implement or enable cognition, and identifying patterns of neural activity that are associated with specific cognitive activities

• Can appear more descriptive than explanatory