What is Temporal Validity?

Last time, we saw that when the results of a study generalise to how people behave in everyday life, we say that…

Ecological validity is the first of the three types of external validity.

The second type of external validity is called temporal validity.

Now, suppose a health researcher is interested in investigating people’s attitudes towards smoking.

Before spending lots of money conducting a big, expensive survey, she decides to find out if anyone has conducted any surveys about attitudes towards smoking already.

After a bit of digging, she finds an article from the 1950s entitled “Attitudes to smoking: a massive survey”, which says that the majority of people think that smoking really isn’t bad for you in any kind of way.

Now even though there’s already a paper researching people’s attitudes towards smoking, the health researcher decides that, since she already has grant money for her research, she might as well conduct her study anyway.

But, the results of her study don’t match up with the 1950s survey; in her study, she finds that the majority of people think that smoking is bad for your health.

So, why don’t the results of the two surveys match up?

Well, society has changed a lot since the 1950s. 

We now know way more about the negative effects that smoking has on a person’s health… for instance, we now know that smoking causes lung cancer.

Because our awareness of the effects of smoking has increased a lot since the 1950s, the results from the 1950s survey don’t generalise to how people feel about smoking today.

Now, when the results of a study generalise across time, we say that the study has temporal validity.

The 1950s smoking survey results don’t generalise across time, so, the survey lacks temporal validity.

Now, suppose a young PhD student decides to try and replicate some famous memory research from the 1960s, showing that people can only remember about 5 words in short-term memory at once.

If she finds that nowadays, people can still only remember about 5 words at once in short-term memory, then the memory research from the 60s has temporal validity.

But if she finds that nowadays, people can remember 10 words at once in short-term memory, then the memory research from the 60s lacks temporal validity.

Now, which of the following examples might lack temporal validity?

This study lacks temporal validity, because musical tastes have changed a lot in the past 100 years.

This study also lacks temporal validity, because the political situation of the world has changed a lot in the past 80 years.

And, finally, this study also lacks temporal validity, because, no one even uses MySpace anymore!

To sum it up, a study has temporal validity when the results of a study generalise across time.