A2 - Psychology - Disadvantages of the scientific method

HideShow resource information

Disadvantages of the scientifc method 

Internal validity

Description: Internal validity is whether a study has tested what it set out to test; the degree to which the observed effect was due to the experimental manipulation rather than other factors such as extraneous variables. Simply, whether what was meant to be tested was tested, and whether this was due to manipulation of the Independant Variable (IV) and not due to Extraneous Variables (EV) which could affect the results.

Disadvatage: There are many possible ways in which the internal validity of a study can be hindered. This could be through things such as:

  • Extraneous variables - something that might influence the outcome of the experiment (time, room temperature, order effects)
  • Researcher bias - the effect the researcher has on the findings.
  • Demand characterisitics - Participants living up to expectations of the researcher.

Internal validty is a disadvanatge because the observed effects on the DV may be due to variables other than the researchers manipulation of the IV.


  • Asch's conformity study had problems with extarneous variables. 
  • May not have demonstrated true levels of conformity as the naive participants did not know any of the other 'participants'; they may have been more conforming had they know the other people in the study, as they wouldn't have wanted others to have a poor opinion of them.
  • Thus leading to the study having low internal validity as Asch didn't successfully measure what he set out to.

External Validity

Description: External Validity refers to the extent to which the findings of research can be generalised to other settings, other times and other people. This generally depends on the sample the researcher has decided to use as to whether it applies outside the laboratory.

Disadvantage: The scientific method is highly artificial, meaning it lacks ecological validity. It also uses restricted samples, meaning it lacks population validity. therefore, the findings of scientific studies can often not be generalised outside of the setting in which it was conducted, both to real life situations and to other people.

Example: Loftus and Palmer's study was very artifical as the participants only watched video clips of car crashes and therefore it lacked ecological validity. However, if it was a real


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all Disadvantages of the scientifc method resources »