Introduction to scientific reasoning
Overview lecture
1. Psychology is a way of thinking (Chapter 1)
2. Sources of information (Chapter 2)
1. Psychology is a way of thinking
Producing vs. consuming resources
We can ask ourselves:
- “Why do psychology students have this course in their program?”
- “Why do psychology students have to know how research is done?
It’s because people in this domain will either be a research producer or a research consumer
• Research producer: produces the research itself
• Research consumer: makes decisions based on evidence (research is done for you)
First example:
The Scared Straight program, made famous by the documentary Scared Straight!, was a
1970s experiment in the United States designed to prevent juvenile delinquency. Teenagers
who were considered at risk of criminal behavior were taken to prisons such as Rahway
State Prison, where they were confronted by real inmates. The prisoners shouted at them,
described the harsh and difficult realities of prison life, and attempted to frighten them into
avoiding crime. The program was based on the idea of deterrence—the belief that if young
people see how terrible prison life is, they will be scared into making better choices.
However, later research showed that the program was often ineffective and, in some cases,
even increased criminal behavior among participants.
Gemaakt door Hafsa Ait Lahcen
,A second example to illustrate the importance of the research consumer:
This example concerns Griet Op de Beeck. She appeared on a television show where she
openly discussed her own mental health struggles. During the program, she stated that she
had become a therapist and was working with the method Internal Family Systems (IFS).
This led to controversy because she does not have a formal academic background in
psychology or therapy.
In the program, she claimed that Internal Family Systems has been scientifically proven to be
effective. Therefore, it is important to critically examine the available research.
When looking at studies on the effectiveness of IFS, several methodological issues arise.
First, some studies used very small sample sizes, which limits the reliability and
generalizability of the results. Second, certain studies did not include a control group. Without
a control group, it is difficult to determine whether the observed improvements were actually
caused by IFS rather than by other factors. As a result, the evidence supporting the
effectiveness of IFS in these studies is not very robust.
A third example: the study by Daryl Bem (2011/2012)
A third example is the study by Daryl Bem, published in
2011 (and widely discussed in 2012). In this study, he
claimed to have found evidence that people can predict
future events, in other words, that future stimuli can
influence present behavior. This idea is known as precognition.
The article consisted of nine experiments. One of the most well-known experiments involved
retroactive priming. In traditional priming experiments, a positive or negative image is first
shown to evoke an emotion. After that, participants see a word and have to categorize it as
pleasant or unpleasant. The idea is that if a positive image is shown before a positive word,
participants respond faster due to the so-called congruence effect.
Bem reversed this design: participants first saw the word, and only afterward a randomly
selected positive or negative image appeared. Despite this reversal, he reported finding a
congruence effect, which would imply that the later image influenced earlier behavior.
After publication, the study received substantial criticism.
First problem: the reported effects were very small. Although they were statistically
significant, statistical significance does not necessarily mean that an effect is strong or
practically meaningful. It is important to consider both effect size and statistical significance.
Second problem: Bem conducted dozens of experiments, but mainly reported the ones in
which he found significant effects. Experiments that did not show an effect were less
emphasized or not reported. This is known as selective reporting or publication bias. By
reporting only significant findings, results may appear convincing even if they are due to
chance.
After the publication of his study, other researchers attempted to replicate the findings. In
many cases, they failed to reproduce the same effects. This contributed to what later became
known as the replication crisis in psychology.
Gemaakt door Hafsa Ait Lahcen
,How scientists work
• Science is based on empiricism
• Scientists test theories
• Scientists form a community
• Scientists work on fundamental and applied problems
• Science is continuously evolving
• Scientists publish their findings in scientific journals
• Scientists communicate with the general public via journalists
Empiricism
The empirical method is based on data obtained through:
• Our senses (sight, hearing, touch..)
• Instruments that assist our senses (thermometer, questionnaires, timer)
• Both quantitative and qualitative methods can be used to collect empirical evidence
Quantitative data= numbers
➔ Most psychological research is quantitative
Empiricists aim to do research in a systematic, rigorous (strict/robust), and replicable manner
Empirical research is better than other data, because the empiricism is not based on own
experiences, intuition, or authority figures
Scientists test theories
The theory–data cycle describes how scientists build knowledge by
moving repeatedly between ideas and evidence: they begin with a theory
that proposes how something works, derive focused research questions
and a testable hypothesis from that theory, design a study and preregister
their plan, collect data, and then evaluate whether the results support or
challenge the original idea; supporting data strengthen confidence in the
theory, while nonsupporting data prompt researchers to revise the theory
or improve the study design, and in either case the updated understanding
feeds back into the next round of questions and experiments, keeping
science continuously self-correcting and evolving.
Gemaakt door Hafsa Ait Lahcen
, Note: There is a difference between exploratory (inductive) and confirmatory (deductive)
research!
• Exploratory (inductive)= tests a prediction you make in advance
o We construct the theory via observation
• Confirmatory (deductive)= looks at data first to see what patterns emerge
The theory–data cycle has a confirmatory approach. Its whole purpose is to take a theory,
derive a specific hypothesis from it, and then collect data to test whether that hypothesis is
supported or not. That’s the essence of confirmatory science: you make predictions before
seeing the data and then evaluate whether the evidence confirms or challenges those
predictions. Exploratory research, by contrast, looks for unexpected patterns without starting
from a specific hypothesis.
Study by Harlow: Cupboard theory vs. Contact comfort theory
Harry Harlow’s 1958 study tested two competing
explanations for why infant animals form attachments to their
mothers: the cupboard theory, which claimed that infants
bond with their mother because she provides food, and the
contact comfort theory, which argued that attachment is
driven by warmth, softness, and affection rather than
feeding. To test these theories scientifically, Harlow followed
the full theory–data cycle: he started with the two theories,
turned them into a research question (“Why do infants
attach?”), designed an experiment, preregistered a hypothesis, collected data, and then
evaluated which theory the evidence supported. In the experiment, baby monkeys were
placed in a setup with two surrogate “mothers”: one made of bare wire that provided milk,
and another covered in soft cloth that offered warmth and comfort but no food. By measuring
how much time the infants spent with each surrogate, Harlow found that the monkeys
overwhelmingly clung to the soft, comforting mother rather than the wire mother that fed
them. These data contradicted the cupboard theory and supported the contact comfort
theory, showing that affection and physical comfort—not food—are the primary drivers of
attachment.
Gemaakt door Hafsa Ait Lahcen
Overview lecture
1. Psychology is a way of thinking (Chapter 1)
2. Sources of information (Chapter 2)
1. Psychology is a way of thinking
Producing vs. consuming resources
We can ask ourselves:
- “Why do psychology students have this course in their program?”
- “Why do psychology students have to know how research is done?
It’s because people in this domain will either be a research producer or a research consumer
• Research producer: produces the research itself
• Research consumer: makes decisions based on evidence (research is done for you)
First example:
The Scared Straight program, made famous by the documentary Scared Straight!, was a
1970s experiment in the United States designed to prevent juvenile delinquency. Teenagers
who were considered at risk of criminal behavior were taken to prisons such as Rahway
State Prison, where they were confronted by real inmates. The prisoners shouted at them,
described the harsh and difficult realities of prison life, and attempted to frighten them into
avoiding crime. The program was based on the idea of deterrence—the belief that if young
people see how terrible prison life is, they will be scared into making better choices.
However, later research showed that the program was often ineffective and, in some cases,
even increased criminal behavior among participants.
Gemaakt door Hafsa Ait Lahcen
,A second example to illustrate the importance of the research consumer:
This example concerns Griet Op de Beeck. She appeared on a television show where she
openly discussed her own mental health struggles. During the program, she stated that she
had become a therapist and was working with the method Internal Family Systems (IFS).
This led to controversy because she does not have a formal academic background in
psychology or therapy.
In the program, she claimed that Internal Family Systems has been scientifically proven to be
effective. Therefore, it is important to critically examine the available research.
When looking at studies on the effectiveness of IFS, several methodological issues arise.
First, some studies used very small sample sizes, which limits the reliability and
generalizability of the results. Second, certain studies did not include a control group. Without
a control group, it is difficult to determine whether the observed improvements were actually
caused by IFS rather than by other factors. As a result, the evidence supporting the
effectiveness of IFS in these studies is not very robust.
A third example: the study by Daryl Bem (2011/2012)
A third example is the study by Daryl Bem, published in
2011 (and widely discussed in 2012). In this study, he
claimed to have found evidence that people can predict
future events, in other words, that future stimuli can
influence present behavior. This idea is known as precognition.
The article consisted of nine experiments. One of the most well-known experiments involved
retroactive priming. In traditional priming experiments, a positive or negative image is first
shown to evoke an emotion. After that, participants see a word and have to categorize it as
pleasant or unpleasant. The idea is that if a positive image is shown before a positive word,
participants respond faster due to the so-called congruence effect.
Bem reversed this design: participants first saw the word, and only afterward a randomly
selected positive or negative image appeared. Despite this reversal, he reported finding a
congruence effect, which would imply that the later image influenced earlier behavior.
After publication, the study received substantial criticism.
First problem: the reported effects were very small. Although they were statistically
significant, statistical significance does not necessarily mean that an effect is strong or
practically meaningful. It is important to consider both effect size and statistical significance.
Second problem: Bem conducted dozens of experiments, but mainly reported the ones in
which he found significant effects. Experiments that did not show an effect were less
emphasized or not reported. This is known as selective reporting or publication bias. By
reporting only significant findings, results may appear convincing even if they are due to
chance.
After the publication of his study, other researchers attempted to replicate the findings. In
many cases, they failed to reproduce the same effects. This contributed to what later became
known as the replication crisis in psychology.
Gemaakt door Hafsa Ait Lahcen
,How scientists work
• Science is based on empiricism
• Scientists test theories
• Scientists form a community
• Scientists work on fundamental and applied problems
• Science is continuously evolving
• Scientists publish their findings in scientific journals
• Scientists communicate with the general public via journalists
Empiricism
The empirical method is based on data obtained through:
• Our senses (sight, hearing, touch..)
• Instruments that assist our senses (thermometer, questionnaires, timer)
• Both quantitative and qualitative methods can be used to collect empirical evidence
Quantitative data= numbers
➔ Most psychological research is quantitative
Empiricists aim to do research in a systematic, rigorous (strict/robust), and replicable manner
Empirical research is better than other data, because the empiricism is not based on own
experiences, intuition, or authority figures
Scientists test theories
The theory–data cycle describes how scientists build knowledge by
moving repeatedly between ideas and evidence: they begin with a theory
that proposes how something works, derive focused research questions
and a testable hypothesis from that theory, design a study and preregister
their plan, collect data, and then evaluate whether the results support or
challenge the original idea; supporting data strengthen confidence in the
theory, while nonsupporting data prompt researchers to revise the theory
or improve the study design, and in either case the updated understanding
feeds back into the next round of questions and experiments, keeping
science continuously self-correcting and evolving.
Gemaakt door Hafsa Ait Lahcen
, Note: There is a difference between exploratory (inductive) and confirmatory (deductive)
research!
• Exploratory (inductive)= tests a prediction you make in advance
o We construct the theory via observation
• Confirmatory (deductive)= looks at data first to see what patterns emerge
The theory–data cycle has a confirmatory approach. Its whole purpose is to take a theory,
derive a specific hypothesis from it, and then collect data to test whether that hypothesis is
supported or not. That’s the essence of confirmatory science: you make predictions before
seeing the data and then evaluate whether the evidence confirms or challenges those
predictions. Exploratory research, by contrast, looks for unexpected patterns without starting
from a specific hypothesis.
Study by Harlow: Cupboard theory vs. Contact comfort theory
Harry Harlow’s 1958 study tested two competing
explanations for why infant animals form attachments to their
mothers: the cupboard theory, which claimed that infants
bond with their mother because she provides food, and the
contact comfort theory, which argued that attachment is
driven by warmth, softness, and affection rather than
feeding. To test these theories scientifically, Harlow followed
the full theory–data cycle: he started with the two theories,
turned them into a research question (“Why do infants
attach?”), designed an experiment, preregistered a hypothesis, collected data, and then
evaluated which theory the evidence supported. In the experiment, baby monkeys were
placed in a setup with two surrogate “mothers”: one made of bare wire that provided milk,
and another covered in soft cloth that offered warmth and comfort but no food. By measuring
how much time the infants spent with each surrogate, Harlow found that the monkeys
overwhelmingly clung to the soft, comforting mother rather than the wire mother that fed
them. These data contradicted the cupboard theory and supported the contact comfort
theory, showing that affection and physical comfort—not food—are the primary drivers of
attachment.
Gemaakt door Hafsa Ait Lahcen
