So this week I’ve decided to debate on laboratory and natural experiments, hopefully ending up with a blog a lot shorter than last week’s!
Right well I’m sure we all know the basics of a laboratory experiment. In general participants come into a laboratory (obviously) which is essentially a controlled environment. The researcher generally has something (a hypothesis) that they want to test and so they manipulate the independent variable to see if it has an effect on the dependent variable- the thing they’re measuring. Craik and Lockhart (1972)* conducted a laboratory experiment investigating their Levels of Processing Model of memory. They suggested that information could be encoded into memory at a shallow, deeper or deepest level and so to test this they conducted an experiment in which participants’ memory for different questions was tested. For example they were asked questions such as:
- Is the word FISH in lower case or capital letters? (Shallow processing-appearance of the word)
- Does the word STYLE rhyme with ‘pin’? (Deeper processing- appearance and sound of the word)
- Is the word PANCAKE a form of transport? (Deepest processing- the actual meaning of the word)
So in their study Craik and Lockhart manipulated the independent variable (the types of questions) and measure the dependent variable (how well/deeply participants remembered the question). As you would expect, the question that required processing the actual meaning of a word was remembered significantly better. However, just because this study was a lab experiment doesn’t mean it was perfect. There are several positive and negative aspects of laboratory experiments that I will now discuss, with reference to Craik and Lockhart. So let’s evaluate.
Firstly, laboratory experiments have a high level of internal validity as they are conducted in a controlled environment in which the experimenter is responsible for manipulating the variables. Because of the controlled environment it is also easy to replicate the experiment as there are usually standardised procedures in place, and as we all know replication is an important aspect of a science. And what about cause and effect? Well laboratory experiments are much better at showing us cause and effect relationships than natural experiments as the control over variables means that there are less extraneous variables present. But now for the bad bits…
The Craik and Lockhart study has been criticised as lacking validity and representativeness. This is mainly because the study has internal validity, which is good, but as a result it lacks external and ecological validity- thus making it difficult to generalise outside of the laboratory setting. Generalisation issues also occur because it may be difficult to operationalise certain variables. For example Craik and Lockhart were interested in the “depth of processing”* however something that may be seen as deep by one individual may actually only require shallow processing in another. Laboratory experiments can also be criticised on the grounds that.
Laboratory experiments are good if we want to find out if one thing causes another. However as they are conducted in an ambiguous environment participants may not react how they would in real life. For example, testing reaction time in a laboratory may produce a different result than testing driving reaction times in real life.
Before I rant on about lab experiments forever (you can probably tell I’m not a fan of them in psychology) let’s discuss natural experiments.
Instead of manipulating the independent variables in a lab experiment, a natural experiment looks for naturally occurring variables in the environment. For example, comparing the school grades of boys with those of girls would be a natural experiment as no variables have been manipulated, researchers are simply comparing what they have available in front of them. However, many people suggest that natural experiments are not true experiments as there is no control over extraneous variables and if participants are not aware that they are being observed is it really ethical? I suppose you could argue that as participants are none the wiser they are not going to come to any harm and therefore don’t really need to consent to take part.
Also, natural experiments are pretty cheap and easy to conduct. There are many naturally occurring events that psychologists are able to study through natural experiments. For example, in the case of Oxana** – a young girl who was left out with the dogs in the garden at her parent’s house when she was a child and began to behave like them, barking instead of talking and walking on all fours instead of upright – it would be incredibly unethical to put a child in this situation to study. However, psychologists were able to study her behaviour through the naturally occurring event and apply it to prior knowledge they had about nurture in a child’s environment and behaviour.
I guess you can say that lab and natural experiments have their positives and also their negatives. You have to think, lab experiments may be more scientific but in psychology the findings from them are often not as representative as they could be. And whilst natural experiments are more representative of everyday life they lack the control of lab experiments.