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Casey et al - Evaluation - Coggle Diagram
Casey et al - Evaluation
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Background
Sample of 4 year old children performed in delay of gratification task. They were given a marshmallow and told they can have it now or they can wait 15 minutes and get two. Of those who attempted to delay, 1/3 deferred gratification long enough to get second treat
Method
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Design: Quasi experiment, IV: whether each participant is high or low delayer. Longitudinal study.
Sample: 562 4 year olds in 1960s. 155 completed self control scale in 20s and 135 in 30s . 59 were above/below average. 27 agreed to neuroimaging study
Procedure
Ex1: Cool version -> Participant told gender of target. 4 conditions: male/female go, male/female no go. 160 faces projected for 500ms with 1 second interval. Button press for go, no press for no go. Hot version -> Same but faces are happy/fearful
Ex2: fMRI used whilst similar go/no go task carried out. fMRI imaging of right prefrontal cortex and ventral striatum taken from 26 participants
Results
Participants who were low delayers as children showed more difficulty supressing responses to hot cues as adults than high delayers
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Conclusions
resistance to temptation as child is stable individual difference that predicts biases in brain circuitries that integrate
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Validity
High construct validity as it fully operationalises DV in experiment perform two they performed hot no and go trials. The ventral striatum had higher activity in these trials. Shows that based on activity and regions of brain that the neural activity was affecting their behaviour on whether they had delayed gratification or not
Low internal validity because may have responded to demand effects. For example, were given a questionnaire about self-control and therefore in experiment one, in the go/no-go trials, they could have guessed that it was about whether they could delay gratification. Therefore, the experiment may have been measuring the altered behaviour and what the participants believe the experiment wants their behaviour to be
Sampling bias
Casey's study may not be biased due to the sample size used in the study. At the beginning of the study, the sample consists of 562 four year old nursery pupils. This shows that there may not be a bias as, due to the size of the sample, it is unlikely that the sample is not representative of most characteristics
Casey's study may be biased later on because of the amount of ps that dropped out of the study. When ps returned for the self control scales, the number of ps fell to 135 by their 30s and dropped to 56 when asked to participate in a longitudinal study. Due to sample attrition, this may cause a bias in the sample as people who have agreed to stay have certain characteristics that have made them continue with this study. This characteristic may also be that they're high delayers as they have continued with the study that takes place over a long period of time