B. Introduction

The introduction provides background information, as well as a rationale for the investigation. It is important that this section of the paper clearly sets out what you are going to investigate, and why the investigation is important.

The introduction is an important part of your report.  In addition to describing the study that you are going to replicate, it also helps the reader understand the importance of this study and the theory upon which it is based.  When thinking about writing this section, you should try to explain this as if you are explaining it someone how has never studied this area of human behaviour before.  Don't make assumptions about what the reader knows about your topic.

The introduction includes the following information:

  • A general introduction to the psychological question under investigation.
  • A description of the theory or model upon which the study is based and an explanation of how the theory or model link to your own experiment.
  • Definition of any terminology necessary for understanding your study.
  • A description of the study that you are replicating.
  • A statement of the aim of your study and an explanation of its relevance. Why is this an important area of investigation?
  • The introduction should end with a statement of the null and research hypotheses specific to your study —that is, a clear prediction of what you expect to find through your investigation. The independent and dependent variables should be fully operationalized in the hypotheses.

The introduction should focus on the theory or model that is investigated and this should include details of the study that is being replicated and how that study investigated the theory or model. The study to be replicated should be described in terms of its the aim, procedure, findings, and conclusions. You will need this to make comparisons of your own results to those of the original study in the final section of the report.   

After explaining the original experiment, you should state why you think the theory or model of the original study is important to investigate, which is also explains  why the study could be worth replicating. What value does this research have in our understanding of human behaviour? You should finalize your introduction by clearly stating the aim of your research. For example:

  • Aim: to investigate the effects of particular adjectives on the formation of impressions in bilingual high school students.
  • Aim: to investigate the effect of leading questions on estimation of speed in a car accident in 18-year-old American students with driving experience.

The introduction should then end with a clear statement of the investigation’s null and research hypotheses.  The variables in the hypotheses must be clearly operationalized – and any modifications made to the original study should be justified.

Research and null hypotheses

In experimental research, psychologists first must state what they predict will happen. To do this, we state a null and a research hypothesis.

The null hypothesis states that there will be no effect of the manipulation of the independent variable on the dependent variable -in other words, the null hypothesis states that any difference found is due to chance and not the manipulation of the independent variable. In fact, it is the null hypothesis that is tested as a researcher normally wants this to be refuted.

The research hypothesis predicts how the independent variable is expected to affect the dependent variable. Simply stating that the independent variable will affect the dependent variable is not enough; the actual effect should be clearly predicted.

A well-written hypothesis is clearly operationalized. This means that the IV and DV are stated in a way that is measurable. Simply stating that “Noise will have an effect on learning” is not an operationalized hypothesis. What is meant by “noise?” How are you going to measure “learning?” An operationalized hypothesis for this study might be: Participants who listen to classical music while reading a description of a new school (IV) will be able to recognize more details about the school from a list of statements (DV) than students who read the text in silence.

The aim was to investigate whether there is a higher recall of words using the method of loci in free recall than using no memory technique.

The null hypothesis for this experiment would be There will be no significant difference in the number of details about a school that a participants will recognize from a list of statements when listening to classical music or under silent conditions.

Remember that the goal of research is not to prove the research hypothesis correct, but to refute the null hypothesis. In other words, we want to establish that there actually is a relationship between the IV and the DV, and that any results we have obtained were not just due to chance. When we can statistically establish that the results are not due to chance, the data are significant. When the data are significant, we refute the null hypothesis. When our data are not significant, we retain the null hypothesis. This simply means that the IV did not cause changes in the DV.

Sample Introduction

Cognitive psychologists argue that we are cognitive misers – that is, “humans, valuing their mental processing resources, find different ways to save time and effort when negotiating the social world (Fiske & Harris, p 2).”  One of the ways in which we do this is by using heuristics.  Heuristics can be defined as “judgmental shortcuts that generally get us where we need to go – and quickly – but at the cost of occasionally sending us off course (Gilovich & Savitsky, p 34). ”

One of these heuristics, which helps us to make quick decisions about information, is called anchoring bias.  Anchoring bias is defined as the common human tendency to rely too heavily, or "anchor," on one trait or piece of information when making decisions (Anchoring bias). Anchoring often happens because there is not enough information for the individual to make a decision, so the initial information provided serves as a basis for making further decisions.  This can have serious implications.  For example, Englich & Mussweiler (2001) found that anchoring bias plays a significant role in determining sentencing in courtrooms.  When told that the maximum sentence was 34 months, jurors recommended on average eight months longer in prison that when told that the maximum sentence was 12 months – for the same crime.  In this case, the juror would not have a lot of experience in making these decisions, so the maximum sentence as stated by the judge would then influence the decision for how long the accused should be in prison.

One of the original studies on anchoring bias was done by Tversky & Kahnemann (1974).  In this study, high school students were used as participants.  Participants in the “ascending condition” were asked to quickly estimate the value of 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8. Those in the “descending condition” were asked to quickly estimate the value of 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1. Since we read from left to right, the researchers assumed that group 1 would use "1" as an anchor and predict a lower value that the group that started with "8" as the anchor.  The expectation was that the first number seen would bias the estimate of the value by the participant. The researchers found that the median for the ascending group was 512; the median for the descending group was 2250. The actual value is 40320. 

Based on this study, the aim of our investigation is to see if anchoring bias plays a role in mathematical estimation among international high school students. Teachers of mathematics often ask students if they think that their answers look reasonable. It is possible that anchoring bias would affect this. So, we decided to use IB HL mathematics students for this study so that we could eliminate the confounding variable of weak mathematics skills.

Null hypothesis: There will be no significant difference in the responses given by IB higher level math students when asked to estimate the value of 8!  when the problem is presented in either ascending or descending order.

Research hypothesis: IB higher level math students will estimate a higher value for 8! when the problem is presented in descending order vs. in ascending order.

519 words

Works cited

Anchoring bias in decision-making, Science Daily, retrieved February 28, 2016. Available at: https://www.sciencedaily.com/terms/anchoring.htm

Englich, B., & Mussweiler, T. (2001). Sentencing under uncertainty: Anchoring effects in the courtroom. Journal of Applied Social Psychology, 31, 1535–1551.

Fiske, S.T., & Taylor, S.E. (1991). Social Cognition (2nd ed.). New York: McGraw Hill.

Gilovich, T. & Savitsky, K. (1996). Like goes with like: The role of representativeness in erroneous and pseudoscientific beliefs. Skeptical Inquirer.

Tversky, A.; Kahneman, D. (1974). "Judgment under Uncertainty: Heuristics and Biases". Science 185 (4157): 1124–1131.

Comments on the introduction

Paragraph 1: Notice that important terms are defined and the definitions are cited.  Don't just make up a definition, use what is recognized by psychologists as an "official definition" of the terms.

Paragraph 2: The theory is described and its importance is explained using an example.

Paragraph 3: The study to be replicated is identified and correctly cited. The procedure of the study is not only described, but its rationale is explained. There is a clear statement of the original results that will allow for later comparison in the evaluation section of the report.

Paragraph 4: The aim of the study is clearly stated with reference to the population to be studied.  The rationale for both the study and the choice of sample is clearly explained.

How you are assessed 

The following table is the assessment rubric used to award marks for your introduction.

Marks Level descriptor
  • Does not meet the standard below.
  • The aim of the investigation is stated but its relevance is not identified.
  • The theory or model upon which the investigation is based is identified but the description is incomplete or contains errors.
  • Null and/or research hypotheses are stated, but do not correctly state the independent and/or dependent variables.
  • The aim of the investigation is stated and its relevance is identified but not explained.
  • The theory or model upon which the investigation is based is described but the link to the investigation is not explained.
  • The independent and dependent variables are correctly stated in the null and/or research hypotheses, but not operationalized.
  • The aim of the investigation is stated and its relevance is explained.
  • The theory or model upon which the investigation is based is described and the link to the investigation is explained.
  • The independent and dependent variables are stated and operationalized in the null and research hypotheses.

Next page: Writing the exploration

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Comments 18

Nikki Rotkosky 30 January 2018 - 21:23

The works cited are going in as footnotes or is this based on which format we use - I have been using APA in which case the works cited is at the end. Is this acceptable under the new guidelines?

John Crane 31 January 2018 - 20:13

Dear Nikki - students should not use footnotes. Please have them use APA and put works cited at the end of the paper.

Steven Morris 2 May 2018 - 12:32

Hi John,
My students and I are having trouble figuring out this part of the rubric.
"The theory or model upon which the investigation is based is described and the link to the student's investigation is explained."
What exactly might this look like? For example, in Loftus and Palmer, how would they explicitly link schema theory/theory of reconstructive memory to their own investigation? Would something like this work? "My investigation will allow me to infer whether or not misleading, post-event information really does distort our memory of an event, and will therefore test the theory of reconstructive memory."

Steven Morris 2 May 2018 - 12:33

*I meant to highlight this part "...and the link to the student's investigation is explained."

John Crane 3 May 2018 - 05:17

Dear Steven

This is where it is helpful for students to read the original study. Loftus and Palmer did not base their study on schema theory. They were investigating the "misinformation effect." This should be explained in some detail in the introduction and then there results linked to the theory in the evaluation.

Steven Morris 8 May 2018 - 08:10

Thanks for the message, John. You make a good point, L&P do not mention schemas at all in the original.

Would you be able to shed any further light on how a student can 'explain the link between background theory and the student's investigation' in the introduction section. I am giving student's feedback on their intro this week and I am struggling to understand what the IB are actually looking for here in the new rubric.

John Crane 8 May 2018 - 13:54


I think that if they discuss reconstructive memory and the concept of post-event interference (misinformation effect), they should be fine. In their evaluation they could even mention the role that schema potentially played in the final outcome of their study.

Steven Morris 10 May 2018 - 08:58

Hi John,
First of all, thanks for answering my numerous questions. I really do appreciate the time you put in and your generosity with expertise.
Building upon your response to Xiaolo above, does the relevance of the aim have to be specific to the target population, or can it be society in general?
I feel that this works sometimes (like in the K&T example you put in the example above), whereas sometimes a study's relevance goes way beyond high school students.
Thus my students are shoe-horning in ideas that are relevant to 'Turkish high-school students' in order to meet this criteria whilst I'm advising them to ignore much more interesting points which are relevant to wider society.

John Crane 10 May 2018 - 13:05

Dear Steven

It can be society in general, which means it should also be relevant to the population being studied. You are right that sometimes there is a significant difference between the effect on the general population vs. the population used in the study - and sometimes a more general approach is appropriate. Either way, it is important for students to explain why the research is justified.

Bhawna Egbert 25 June 2018 - 11:24

Hi John, Does this sample introduction come under the full marks mark band or is there some room from improvement..Can I give it a 6??

John Crane 25 June 2018 - 20:49

Dear Bhawna

Yes, it is meant to be an exemplar of what should be in an introduction. You could give it full marks.

Tripti Rathore 20 July 2018 - 05:17

Dear John,
My students are replicating Loftus and Palmer (1974) first experiment so do they still need to link it with "misinformation effect" or they are going to link it with "reconstructive memory" of Bartlett.

Tripti Rathore 20 July 2018 - 05:18

Also how many research studies should be there in introduction. They need to mention only the research study which they are replicating or they have to give evidence for the theory as well.

John Crane 22 July 2018 - 19:01

Dear Tripti,

I really don't see how it links to Bartlett, except to say that memory is reconstructive. I think that it would be a weak paper to not base it on the theory that Loftus herself was studying. The IA guide states that they are to only describe the study that they will be replicating. They are not supposed to have any other research in the introduction, only an explanation of the theory.

Tripti Rathore 23 July 2018 - 17:06

Thanks a ton

SREEJITH A.P 26 July 2018 - 12:00

Dear sir,
I have some doubts in IA -
1. One of my student did IA with the help of another child (from the same school and different subject), is this acceptable? because there is a clause in the IB guide, "Students may choose group members who share a common interest or they may join a group and then decide on an area for study within that group". If yes, Please guide me what all are the proved the child need to submit. Otherwise this will be same like individual project.
2. Do we need page wise citation or in text citation? or only reference in the last.
3. In the introduction, how many back ground/supporting studies are we suppose to give?

Thank you

Thank you


John Crane 27 July 2018 - 12:11

Dear Sreejith

1. If the other student is not in psychology, then this is not a problem. The only student who will submit anything is the student in your course.
2. You should have in-text citation and references at the end of the report.
3. The student needs to discuss the theory on which the study is based - and describe the study that is being replicated. There should not be a long list of supporting studies. One is all that is required.

SREEJITH A.P 28 July 2018 - 02:57

Thank you sir, it's a valuable information.