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Principles of Psychology: Contemporary Perspectives

Research in Focus

Accessible, engaging, innovative: this new book encourages critical thinking and provides the most student-friendly introduction to the science of psychology.

Principles of Psychology: Contemporary Perspectives Accessible, engaging, innovative: this new book encourages critical thinking and provides the most student-friendly introduction to the science of psychology.

One of the unique things about this textbook is the lively and effective pedagogical scheme that helps first year undergraduates develop the skills and approaches necessary for success.

Read on to find out more, and to view examples of the ‘Research in Focus’ and ‘Master your Methodology’ features used throughout the text.

Marshmallow Study


If you want to really understand something, go to the source.
Reading primary sources is a very important part of learning to think like a psychologist. Original research papers and conference proceedings can allow a student to deepen their understandings of how conclusions are reached, and play an important role in starting to interrogate evidence and think critically.

However, engaging with primary sources can be daunting for students, and getting used to reading them can feel like a culture shift from pre-degree study. 

Our ‘Research in Focus’ feature supports engagement with primary sources by guiding students through classic experimental studies and more recent research.

This feature summarises research papers according to their aims, methods, results and conclusions. These present a clear overview of the paper, get students familiar with the structure of research papers, and provide a framework to guide their future reading.

At the end of each 'Research in Focus' feature is our ‘Master your Methodology’ feature, a set of questions designed to prompt students to critically assess the design of the study, the methods of data collection and analysis, and the conclusions reached.

Principles of Psychology: Contemporary Perspectives

An example from the book – The original ‘Marshmallow Study’

 Although this classic study has become known as the ‘Marshmallow Study’, ironically the original study method didn’t involve marshmallows at all!


Mischel, W. and Ebbesen, E.B. (1970). Attention and delay of gratification. Journal of Personality and Social Psychology, 16, 329–37.

marshmallowAim: The aim of the study was to investigate the role of cognitive processes on children’s ability to delay gratification. More specifically, to test whether having small immediate rewards and larger delayed rewards in view affected children’s tendency to wait for the larger reward. It was predicted that children would find it hardest to delay gratification when neither the immediate nor the delayed reward was visible.

Method: Participants were 16 girls and 16 boys with a median age of 4 years 6 months, selected from the Stanford University nursery. Four males and four females were randomly assigned to each of four conditions. In all conditions experimenters led each child to a small room containing a table, two chairs, and a few toys. On the table were a small snack of two pretzels (a savoury snack) and a second, larger snack consisting of five pretzels and two biscuits. The experimenter told the child that they would leave the room and that the child could eat the small snack immediately or have the larger snack if they sat still and waited for the experimenter to return. At this point the experimenter was informed which condition they were administering. In one condition both small and large snacks were left visible. In two further conditions each snack was concealed with an upturned cake tin and in the final condition both snacks were covered. The experimenter then left the room, returning either after 15 minutes or when the child ate the small snack, whichever was sooner. The dependent variable, time of delayed gratification, was measured from the experimenter leaving. Observers recorded the children’s behaviour.

Results: The opposite of the predicted outcome was found. None of the children managed to wait 15 minutes for the large snack (mean waiting time = 1.03 minutes) when both were visible whereas 75% waited the full 15 minutes (mean waiting time = 11.29 minutes) when neither was visible. Only 25% delayed gratification for 15 minutes when one snack was visible, regardless of which snack it was. These differences were statistically significant. Children who successfully delayed gratification tended to distract themselves; for example, by playing or singing whilst sitting still.

Conclusion: Counter to stereotypes, many of the children are able to delay gratification provided they do not have to look at rewards. The visibility of rewards exerts a powerful influence on the ability to delay gratification. Successful delay of gratification is associated with successful distraction but this is inhibited by the presence of visible rewards.


  1. This study primarily gathered quantitative data. Explain how the gathering of supplementary qualitative data (the observations of children) enhanced the results.
  2. The experimenters were informed which condition they were administering after they had completed the initial phase of the procedure to avoid demand characteristics. Explain what demand characteristics are and why they can be a problem in experimental research.
  3. The experiment involved a between-groups design. Explain the advantages and disadvantages of this design and suggest why it might have been used in this study.

Principles of Psychology: Contemporary Perspectives