Physiological Approach (4)
A problem with the physiological approach is that by using such a scientific approach and testing behaviour in laboratory conditions the measurement of behaviour often lacks validity. For example, Dement and Kleitman measured sleep in laboratory conditions which is not typical of how people normally sleep. Therefore asking people to sleep with electrodes attached to their scalp and face is low in ecological validity. Similarly Sperry’s participants were asked to complete unusual tasks which again are not typical of everyday behaviours. However the use of this laboratory approach does mean that the researchers have more control of their procedures ensuring that extraneous variables can be controlled
A further problem with the physiological approach is that because such studies can be costly and time consuming because of the use of sophisticated equipment and lengthy procedures. This often leads to such studies having small samples such as the Dement and Kleitman study which only studied 5 participants in depth. It is possible to argue that such a sample is not representative and therefore we should be careful generalising the results. Furthermore, Sperry was only able to 11 participants because he had a very limited number of participants to choose from, that is participants who had undergone disconnection of the cerebral hemispheres. However the increasing availability of MRI scanners is enabling researchers such as Maguire to increase their sample sizes and in subsequent studies Maguire et al. have been able to scan the brains of many more participants enabling the researchers to have a large database of many more brain scans to choose from.