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  • 00:11

    HARRIET CARMICHAEL: Conditioning, conformity,deprivation, aggression, eyewitnesses memories,these are just some of the thingspsychologists have studied through laboratory experiments.

  • 00:24

    SPEAKER 2: So what exactly is a laboratory experiment?Well, the aim of an experiment isto go beyond just describing somethingand actually test out what's causing it.

  • 00:34

    SPEAKER 3: The method is to manipulate something calledan independent variable to see if it brings aboutchange in something else called a dependent variable.For example, a common way of tryingto isolate the independent variableis by randomly dividing participantsinto an experimental and a control group,and then only apply the independent variable

  • 00:56

    SPEAKER 3 [continued]: to the experimental group.And the laboratory is a closed environmentwhere the influence of other variablescan, as far as possible, be kept constant.

  • 01:06

    SPEAKER 2: So, from here, we can cue in a definition.A laboratory experiment is a testof the effect of one variable on anotherunder closed conditions.

  • 01:17

    HARRIET CARMICHAEL: And you'll also need some applicationto show understanding.For example, in Bandura's Bobo doll experiments,the aim was to test the hypothesisthat aggressive behavior can be learned.

  • 01:31

    SPEAKER 3: In one condition, young childrenobserved an adult role model attackinga large, inflatable doll.In another condition, the role modeldid not behave aggressively.Left alone with the doll, childrenwho had witnessed the aggressive adultwere much more likely to attack the doll themselves.Bandura found that children are more likely to be influenced

  • 01:52

    SPEAKER 3 [continued]: by same sex models.

  • 01:54

    HARRIET CARMICHAEL: The independent variablewas the adult model's behavior manipulatedto be aggressive or non-aggressive.And the dependent variable was the children'ssubsequent behavior towards the doll.

  • 02:09

    SPEAKER 2: In another groundbreaking experiment,Elizabeth Loftus tested where the eyewitnesses memories couldbe influenced by the wording of a question.

  • 02:16

    PROFESSOR ELIZABETH LOFTUS: At first wewere interested in how a question, the way youword a question, could affect the answer that somebodygave you.And we looked at this by showing people films of accidentsand then asking questions about the speed of the vehiclesinvolved in the accident.So some witnesses might be asked,how fast were the cars going when they hit each other?

  • 02:38

    PROFESSOR ELIZABETH LOFTUS [continued]: Others might be asked, how fast were the cars going whenthey smashed into each other?And different verbs of contact were used.

  • 02:46

    HARRIET CARMICHAEL: The independent variablewas the wording of the question, and the dependent variable,the participants' estimation of the speed.

  • 02:55

    SPEAKER 2: Laboratory experimentscan produce very powerful, hard to argue with findings.For example, Bandura's experimentfound that the children who had seen the adult model behaveaggressively towards the doll were more likely to behaveaggressively themselves.Loftus's experiment also produced some very dramaticfindings.

  • 03:15

    PROFESSOR ELIZABETH LOFTUS: We foundthat by just changing a word or two in the question,you could significantly affect the answer that somebody gave.If you asked the smashed question,they told us the cars were going faster than if youasked a question with one of the other verbs like hitor contacted.

  • 03:32

    SPEAKER 2: Laboratory experiments have majorstrengths that other methods just don't.And that's why they're the cornerstoneof scientific research.

  • 03:40

    SPEAKER 3: The major strength of the laboratory experimentis that it's the only method thatallows the research to test and establish causality.It also allows for greater control of variables,increasing the likelihood that it's the independent variableproducing the effect.Third, it's relatively easy to replicate.

  • 04:01

    SPEAKER 3 [continued]: The laboratory experiment gives high reliability.You can do the test again under the same conditionsand see if you get the same results.

  • 04:11

    SPEAKER 2: So it's easy to see whythe laboratory experiment is so widely used in psychology.

  • 04:17

    HARRIET CARMICHAEL: However, in practice,it also has certain weaknesses and limitations.And, again, we can illustrate thesewith Bandura's experiment.First, even in a laboratory setting,it can be difficult to control for confounding variables.For example, there might be other factors

  • 04:37

    HARRIET CARMICHAEL [continued]: such as hormones influencing some children's behavior.Then there may be demand characteristics.For example, in Bandura's experiments,the children might have hit the dolljust because that's what they thoughtthe adults wanted them to do.Another major limitation is the lack of ecological validity

  • 04:59

    HARRIET CARMICHAEL [continued]: in laboratory experiments.For example, there's no way of knowing for sureif the children in Bandura's experimentwould have actually been aggressive in real life.

  • 05:09

    SPEAKER 2: And ecological validityis also an issue in Loftus's experiment.There's no guarantee witnesses wouldhave been so easily influenced in the real world.Indeed, researchers has suggestedthat, in the real world, witnessescan be more resistant to leading questions than participantsin laboratory studies.But remember, these problems and limitations

  • 05:30

    SPEAKER 2 [continued]: don't necessarily apply in the same wayto all laboratory experiments.Take demand characteristics and this example.

  • 05:37

    SPEAKER 5: Can what we do really changethe structure of our brains?Well, in another famous experiment,Eleanor Maguire hypothesized and foundthat, as a result of their constant navigation,London taxi drivers had redistribution of gray matterin their hippocampi.

  • 05:57

    SPEAKER 3: But they haven't lost that part of the brainjust to please Maguire.So demand characteristics wasn't a factor here.Similarly, lack of ecological validityneedn't compromise the findings of all laboratory experiments.For example, tests demonstrating the Stroop effectaren't compromised because they'redone in laboratory, as you'll get exactly the same results

  • 06:18

    SPEAKER 3 [continued]: in the real world.

  • 06:20

    SPEAKER 2: So laboratory experimentshave less strength and limitations,which may apply to a greater or lesser extentto different studies.

Video Info

Series Name: Experimental Research Methods

Publisher: ShortCutstv

Publication Year: 2017

Video Type:Tutorial

Methods: Experimental design, Quasi-experimental designs

Keywords: practices, strategies, and tools

Segment Info

Segment Num.: 1

Persons Discussed:

Events Discussed:



Laboratory experiments are experiments conducted in a lab by manipulating variables.

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Laboratory Experiments

Laboratory experiments are experiments conducted in a lab by manipulating variables.

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