Hendrie studied Yoruba people of Nigeria and compared then with Americans. Both had similar frequency of genes linked to AD but the Yoruba suffered much less from the disorder. This tells us that other factors must be involved. Perhaps it may be the diet of the Yoruba which is low in salt, fat and calories which reduces the risk. However it could be explained by the interactionist approach and the stress diathesis approach.
However even with al the conflicting evidence genes as an explanation for AD must still be taken seriously and scientist shave found that mutations in certain genes lead to plaques in the brain which then leads to death of nerve cells and the onset of AD.
Brain abnormalities
autopsies have revealed differences in the brains of people with AD when compared to one without it. These abnormalities are thought to be the cause of the disorder.
Plaques are deposits of a beta amyloid 42 protein that build up in the spaces between the neurons. These cause problems in the communication between neurons.
Tangles are deposits of the protein tau that accumulate inside the nerve cells.
Granulovacoules are the abnormal appearance of small holes in the nerve cells.
An evaluation point of brain abnormalities is the research and various experiments involving the introduction of beta amyloid protein into the brain of rats, the findings show that both brain damage and memory impairments occur which suggests that plaques may be a cause of AD symptoms in humans.
However a problem with these types of experiments is that the findings cant be generalised to humans because of the physical and psychological differences. It is also unethical to harm animals in the way and could be said that these findings could lead to anthropomorphism.
Environmental factors may also be the cause of memory impairments and brain damage , it can also be explained by the area lived in, diet, upbringing, exercise etc.
Amnesia
Repression:
its been suggested that emotions have been shown to affect memory recall. Emotions can make it difficult to remember or unforgettable.
Freud believed that forgetting is an unconscious motivated process. He came up with motivated forgetting which involved memories which were too emotionally painful to be forgotten using a defence mechanism such as repression and denial. It was said that in repression painful feelings are at first conscious and then are forgotten, but they are stored in the unconscious from where they can be retrieved. Repression can range from momentary lapses of forgetting the details of a horrific event such as a murder. Amnesia can occur in cases where the person has experienced something extremely painful. Freud says that the Oedipus and Elektra complex go through repression whereby the child represses incestuous desires towards the the opposite sex parent and feelings of rivalry towards the same sex parent. Freud didn’t believe all forgetting can be explained through repression but most of it could be due to getting rid of unwanted and unnecessary information.
People may forget experiences because of unpleasant associations for e.g. you may forget your homework because you didn’t want to do it so you simply pushed it out of your mind. This is called suppression which is a conscious or semi conscious behaviour as distinct from repression that occurs unconsciously.
Repression is when the ego protects itself from emotional conflicts. Traumatic events cause anxiety and to reduce this the memory of the even is forgotten, this anxiety maybe expressed through dreams or disordered behaviour as in the the case of little Hams.
The repressed memories continue to affect conscious thought,desire and action even though there is no conscious memory of the traumatic event. Once the traumatic event is repressed from the conscious mind to the unconscious mind it make individual feel better,at least temporarily.
An evaluation point for repression is research by Levinger and Clark, they carried out a study where the P's were given negatively charged words and neutral words. They had to do a word association task whilst having their skin response measured. The P's were then given the cue words again and asked the associations hey had just reported. They found that P's took longer to recall the negatively charged associations than the neutral ones. So it could be said that it took longer to access the unconscious mind for the word associations.
It has been reported that between 20-60% of people undergoing therapy as a result of child sexual abuse report periods in their lives when they could not remember the abuse had taken place. This supports repression as it shows that the memories had been repressed in their unconscious. However it could be said that they did not want to recall the events so therefore pretended they couldn’t remember.
Freud published case studies for his neurotic patients to support his ideas of repression. These have been questioned as inaccurate, however the case studied were unique and one off and can't be generalised as the study took place on white,middle class neurotic women only. The study could be therefore be said to be Oestocentric and culture bias. The study however did have rich qualitative data.
Post traumatic stress disorder is where people re-live traumatic events that have taken place in theory lives. This contradicts repression theory as these people are always remembering it as its not being repressed like Freud says they should.
Robinson et al found that the memory of childbirth pain seems to be forgotten or repressed over time. This supports Freud's theory as child birth can be very traumatic however there are problems with using this evidence to support repression. It is difficult to generalise as the pain of childbirth is more painful and lasts longer than other types of pain.
In conclusion all the theories of forgetting have their strengths but some seem to have more credibility and face validity than others. Psychologists however have considered that forgetting can be induced by memory disorders such as amnesia and dementia.