Dement & Kleitman’s (1957) sleep study concluded that REM sleep was linked with dreams. Participants, when woken up shortly after REM sleep, were more likely to remember their dreams than those who were woken up long after REM sleep. Additionally the researchers concluded that direction of the eye movement also correlated with dreams, for example when dreaming of watching someone climbing a ladder, one participant’s REM pattern was mainly vertical.
There is no denying that this was at the time ground breaking research, using EEG machines (at the time a new technology). However was the sleep from participants really natural? There have been arguments against how natural the sleep from participants was. Firstly participants were in a laboratory which they had never visited before, therefore it was an unusual location for them to sleep, which could have affected their natural sleep. Secondly participants had to sleep with an EEG machine electrodes attached to their heads. Im not sure about you, but this would definitely affect my sleep.
My point is that if participants sleep was unnatural then the whole results from this experiment could be invalid. If the participants were sleeping outside their natural habitat, how can researchers be sure that their sleep was the same as their sleep at home, and that they had similar dreaming patterns, etc. meaning the study had a low ecological validity.
Dement and Kleitman used controls which they claimed would help cause natural sleep, such as not consuming caffeine or alcohol 48 hours prior to the experiment, however they didn’t take into account that the environment the participant had to sleep in.
In conclusion, the method used in Dement and Kleitman’s study lacked validity, however it could be put down too technology of the time, as an EEG machine may have had to be used in a lab setting. Bar the obvious methodological faults in the study, Dement and Kleitman’s research is still widely accepted today in psychology and results have yet to be refuted, meaning currently their results are still valid.