Presentation is loading. Please wait.

Presentation is loading. Please wait.

In defence of lab experiments. Milgram’s lab experiment Teacher Learner Experimente r.

Similar presentations


Presentation on theme: "In defence of lab experiments. Milgram’s lab experiment Teacher Learner Experimente r."— Presentation transcript:

1 In defence of lab experiments

2 Milgram’s lab experiment Teacher Learner Experimente r

3 Milgram’s lab experiment …. except it isn’t an experiment An experiment has ➨ an Independent variable (IV) ➨ Dependent variable (DV) An experiment has ➨ an Independent variable (IV) ➨ Dependent variable (DV) Ivy Devey Ivy Devey Levels of shock were a measurement of obedience. They did not cause the behaviour. Levels of shock were a measurement of obedience. They did not cause the behaviour.

4 Experiments Aim to demonstrate causal relationships. An IV is selected (or levels of an IV). Effects are observed on DV. At the end it should be clear that ‘Behaviour X depended on Y’. Loftus and Palmer LEADING QUESTIONS  IV The verb used  DV estimate of speed LOFTUS AND PALMER– we can say the verb caused the differences in the estimate of speed. MILGRAM– we can’t say that the shock levels caused people to obey. LOFTUS AND PALMER– we can say the verb caused the differences in the estimate of speed. MILGRAM– we can’t say that the shock levels caused people to obey.

5 Milgram experiments Milgram wanted to know what caused obedience so he tried variations – these could be seen as Ivs:  Prestigious vs run down office (IV)  Teacher in different room vs same room (IV) DV = whether person obeyed or not

6 You might be wondering about … Control ➨ Control (manipulate) the IV … changing/varying the level. ➨ Control extraneous variables … keeping variables steady.

7 So … what about laboratories? A facility that provides controlled, contrived conditions. Not just for experiments. Not always artificial.

8 You need the language. But you don’t want to be a slave to the words. We want to get inside the concepts. See the wood for the trees. Homage to formal terms

9

10 Think about this one Memory study looking at gender differences (whether boys or girls have better memories). In a lab … But not a lab experiment. It’s a natural or quasi experiment. So what? We cannot say that gender caused the difference. In fact gender per se cannot have caused it – it is factors that covaried with gender e.g. attitudes to education.

11 Or this one… Participants arrive for an experiment and are asked to sit in a waiting room. They overhear a conversation next door and then a man runs through the room carrying – A pen and with grease on his hands. – A bloodied letter opener. EWT identification less good in the ‘bloody’ condition (33% vs 49% correct identification from set of 50 photographs). Johnson and Scott (1976) Lab or field experiment?

12 Participants arrive for an experiment and are asked to sit in a waiting room. They overhear a conversation next door and then a man runs through the room carrying – A pen and with grease on his hands. – A bloodied letter opener. EWT identification less good in the ‘bloody’ condition (33% vs 49% correct identification from set of 50 photographs). Who cares? Or this one … Johnson and Scott (1976) Lab or field experiment? Can we generalise to everyday? Does the study have ecological validity? Did they test what they intended to test? Were the Ps aware their behaviour was being studied? To what extent did their behaviour mirror everyday behaviour?? To what extent did the task mirror everyday EWT?

13 Validity Loftus et al. (1987) did it with a gun or cheque. Kerri Pickel (1998) did it in a hairdressing salon with a handgun, scissors, man’s wallet and raw chicken. ‘Witnesses’ recall affected by unusualness but not threat. Eye-tracking supports this (Loftus et al, 1987). Unusualness HighLow ThreatHighHandgunScissors LowRaw, whole chicken Man’s wallet

14 Johnson and Scott study was flawed No weapon condition: conversation in adjacent room about equipment failure, holding grease pen, uttered single line and left. Weapon condition: hostile conversation next door plus crashing objects, bloodied letter opener, uttered single line (which was different) and left. DV IV Validity

15

16 We (hopefully) understand experiments and laboratories … … but I haven’t actually defended them yet...

17 In defence of experiments Without experiments we are at the mercy of BAD SCIENCE. Without experiments you cannot claim causes … But people try to do that … The Durham fish oil scandal.

18 Fish oils high in Omega 3 fatty acids. Fish oil capsules given to 5,000 GCSE students in Durham. Great media coverage, including BBC. DV = exam success compared with expected success. But there was no comparison group. They did better than the previous year but this could be due to the Hawthorne effect or general increases. Equazen sell fish oil pills making over £100 million a year. Elliot and his mother PS. A different Durham trial was randomised double-blind controlled – 40% of children did improve – but the students were a special group of 117 primary school children (those not fulfilling their potential at school).

19 In defence of artificial contrived studies Galileo Galilei ( )  Father of modern science.  Objects with different weight drop at same rate.

20  But the feather? There’s the problem of air resistance… Cannon ball and musket ball

21 Tested on the moon Artificial But there is a place for artificial tests.

22 Scope-severity paradox Our judgments tend to be driven by emotional reactions rather than logic. Nordgren and McDonnell (2010) – participants rated severity of a fraud when … – 3 people defrauded by a financial advisor. – 30 people defrauded. Participants who read story with only 3 people rated crime as more serious. Looked at 136 real world cases. – People who harm larger numbers of people get significantly lower punitive damages (e.g. cases harm from asbestos). Two little boys or 2 million deaths from Aids? Two little boys or 2 million deaths from Aids?

23 What have we learned? Deeper understanding of the concepts  Experiment  Laboratory Deeper understanding of the concepts  Experiment  Laboratory The process of science  Depends on lab + experiments.  And verification with real-life events. The process of science  Depends on lab + experiments.  And verification with real-life events. You should be able to provide more thoughtful evaluation. Be proud to be a scientist!


Download ppt "In defence of lab experiments. Milgram’s lab experiment Teacher Learner Experimente r."

Similar presentations


Ads by Google