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Case Study Of Hm Evaluation Report

You need to know most of what's on this page. The case study method features in Unit 1 (Biological) and Unit 2 (Clinical) and can be examined in Unit 3 (Review of Methods). You also need examples of case studies to back up your points.


A case study is an in-depth study of a single person or a small group that all share a single characteristic (like a family).

Case studies focus on abnormal cases: people with deviant behaviour, mental disorders or unusual gifts.

Case studies are usually longitudinal studies - they take place over a period of time, typically months. They record changes in the behaviour and mental state of the participant(s) over that period.

Case studies usually use a mixture of methods. Older case studies (like those by Freud) used to focus on interviews and observations and collect qualitative data. More recent case studies mix this qualitative approach with questionnaires and biological measures (like brain scans or genetic profiling) to collect quantitative data too.

Case studies involve simply recording what happens to - or reconstructing what has already happened to - single participant or group of individuals. This is called the ideographic approach in science - it doesn't test hypotheses, look for causes or try to uncover laws. Case studies allow a researcher to investigate a topic in far more detail than might be possible if they were trying to deal with a large number of research participants.

If a case study shows interesting or unexpected results, it may be followed up with a wider-scale survey or experiment to draw conclusions about people in general - this is the nomothetic approach which tries to uncover scientific laws by "averaging out" the data on lots of individuals.


The Cognitive Contemporary Study by Schmolck et al. also involves looking at a small group of individuals with brain damage - including H.M. It's not really a case study though: it's an experiment that compares the brain-damaged patients' test scores with each other and with a control group. However, Schmolck does single out H.M. to look at individually, so this part of the study could be seen as a case study!
The main application of case studies is in Unit 2 where you study Clinical Psychology. Clinical psychologists use case studies to understand mental disorders better. In particular, case studies can shed light on the difference between normal and abnormal behaviour as well as revealing how effective certain therapies are.

There are different types of case study in clinical psychology:
  • Prospective case studies observe an individual or group of people in order to determine what happens to them. For example, a patient might be watched over time to observe the progression of a mental disorder.Bradshaw (1998) follows a young woman called Carol receiving therapy for schizophrenia.
  • Retrospective case studies look at historical information. For example, psychologists might start with an outcome, such as a mental disorder, and then uncover information about the individual's life to determine risk factors that may have contributed to the illness. A good example is Freud's case study of Little Hans which revealed the boy's Oedipus Complex.
  • Instrumental case studies occur when the individual allows psychologists to understand more than what is initially obvious. A good example is Dr Milner's case study of H.M., which revealed much more about his memory problems than was obvious at first.


This table sums up the strengths and weaknesses of case studies:

Case studies have tiny sample groups - often just a single person.
Remember - a sample isn't unrepresentative just because it's small. A sample of one person could be generalisable if that one person was the most statistically representative person in the world (average height, average IQ, etc.).
The problem with case studies is that they make a point of looking at unrepresentative people - people with deviant behaviour, mental disorders or unusual thought processes (like savants who have incredible memories). These people might not be representative of normal people - they might not even be representative of other unusual people.

On the other hand, the ideographic approach in psychology doesn't try to be generalisable. The point of a case study is to describe in detail. If this description is interesting or unexpected, then psychologists can move on to another nomothetic approach (like an experiment or a correlation) to produce more generalisable findings.

Case studies that are rich in qualitative data may be unreliable. This is because they can be highly subjective: the researcher's own, highly personal, impression of the participant. This is a criticism often leveled at Freud's case studies.

To correct this, researchers often use standardised procedures to gather quantitative data as part of a case study. This often comes from:
  • Biometric data:this might include brain scans, genetic profiles, fingerprints or blood samples
  • Psychometric data:this often comes from filling in questionnaires or solving cognitive tests, like memory tests

Even with standardised procedures, case studies can be unreliable. This is because the participants being studied are often so unusual, it's hard to find anyone similar to replicate the study on. For example, H.M.'s brain damage was similar to, but not the same as, the other brain-damaged participants in the Schmolck et al. study. H.M. was a unique case.

Other participants in case studies are rare but not unique. Bradshaw's case study was of a middle-class young woman with schizophrenia: this is unusual, but not a one-off.

Case studies are particularly useful in clinical psychology because they shed light on unusual conditions that don't fit the patterns of 'normal' behaviour.

Aretrospective case study might suggest factors that could have caused a mental disorder. For example, case studies might explore childhood abuse or neglect in a patient's past as well as genetic differences or brain damage that make a patient unusual.

Prospective case studies help with the evaluation of therapies, by showing whether someone with an unusual disorder benefits from a particular type of therapy. For example, Bradshaw's case study of a young woman with schizophrenia suggests that cognitive therapy can be helpful for this disorder.

Instrumental case studieshelp us understand a disorder better by showing exactly how it affects a sufferer. Milner's case study of H.M.is a good example of this.

However, since these studies are ideographic, psychologists can't derive theories, laws or causal conclusions from them. Further study is needed to test hypotheses and produce generalised conclusions needed to help other sufferers.

The main advantage of case studies is the rich, in-depth data they gather. Case studies "get under the skin" of the participants and help the researchers understand the participants much more thoroughly than any one-off interview or stand-alone experiment would.

Because a case study normally takes a long time to carry out, the participant will get quite used to the researchers and act naturally around them. This reduces the problem of demand characteristics and social desirability bias (but doesn't entirely remove it, especially if the participant only meets with the researcher for a short period at intervals).

For the same reason, researchers get used to the participant and learn to understand and interpret this person's behaviour. This reduces the problem of ethnocentrism and cultural bias (but again, doesn't entirely remove it).

However, this can produce a new problem. In a case study, researcher and participant tend to develop a bond and a relationship forms between them. In particular, the researcher can get to know the participant pretty intimately. This can lead to loss of objectivity.
If you think about it, the whole point of a case study is to see the research participant "as a person" - but once you view someone as a person, it's hard to study them objectively. This is particularly a problem when studying people who have been through difficult experiences.

The intimacy that case studies create between researcher and research participant can lead to ethical problems.

The ethical principle of Integrity demands that researchers conduct themselves professionally - this involves keeping a professional distance between yourself and your research participant. The researcher isn't supposed to befriend the participant or get romantically involved, but this also includes not promising favours or help that you can't deliver. This is particularly a problem when studying participants who are in custody, suffer drug addiction or have deviant fantasies.

A related problem comes from the principle of Minimising Harm, which states that a researcher should not "normalise" unhealthy behaviours. Participants who have delusions or deviant fantasies might feel encouraged if a psychologist appears to sympathise with them.

Social responsibility is important in ethical research. Studying rare or unusual cases is important, but researchers need to bear in mind the effect that this can have on public opinion. This particularly applies to case studies of serial sex offenders, terrorists or murderers because of the danger of "copycat" crimes or of creating stereotypes of minority groups.
My favourite FICTIONAL case study is in the 1991 film "Silence of the Lambs", when trainee FBI agent Clarice Starling (Jodie Foster) is sent to carry out a case study of imprisoned serial killer Hannibal Lecter (Anthony Hopkins). This is an instrumental case study: Starling's boss hopes Lecter's psychology will shed light on another serial killer case. The relationship between Starling and Lecter illustrates all the issues in case studies, especially objectivity and detachment. Watch it: it won all of the "Big Five" Oscars (Film, Directer, Screenplay, Actress, Actor).
Start with an evaluation point and back it up with evidence.
Evaluation + evidence = "logical chain of reasoning"
Issues & Debates (like ethics) make great conclusions

How to write a 8-mark answer

Evaluate the use of case studies as they are used in psychology. (8 marks)
  • A 8-mark “evaluate” question awards 4 marks for describing the case study method (AO1) and 4 marks for evaluating it (AO3). You need a conclusion to get a mark in the top band (7-8 marks). "Case studies" turn up in the Specification for the Biological Approach but could be the basis of a 20 mark question in Unit 2.

Case studies tend to be high in validity because they collect in-depth descriptive data, often over a long period of time. This produces great understanding of the participant. For example, Scoville & Milner's case study of H.M. revealed his memory problems.

Because of this intimacy, participants in case studies often show less demand characteristics and social desirability bias because they act naturally around the researcher. For example, Little Hans acted naturally around his father in Freud's case study.

This intimacy can lead to problems if the researcher loses his or her objectivity and starts to regard the research participant as a friend. This is particularly likely in a prospective case study where the researcher observes the subject growing up.

It can also lead to ethical problems if the researcher loses their professional detachment. Researchers should not form relationships with vulnerable clients or make promises they cannot carry out. This would break ethical guidelines from the BPS and the HCPC.

In conclusion, case studies are a great way to get "under the skin" of unusual or difficult individuals but they have to be monitored carefully to remain objective and professionally detached. An ethics panel is one way of doing this.

  • Notice that for a 8-mark answer you don’t have to include everything about case studies. I haven’t explored generalisability problems or instrumental case studies. But it is a balanced answer - half description, half evaluation.


In Unit 1, the Cognitive Approach requires that you understand case studies and the case of H.M. in particular. H.M. was studied for his entire adult life after his operation. The 1957 case study cited above was simply the first of many carried out by Brenda Milner and her former-student, Suzanne Corkin.
This casestudy was carried out by William Scoville (left) and Brenda Milner (below left) in the 1950s. It was a key piece of research that established that memory is linked to the hippocampus and composed of different functions.

This research is significant for students in other ways:
  • It shows how scientific research proceeds, because before this case study, psychologists assumed memory was a single function that occurred throughout the brain. This study demonstrated that memory consists of different functions linked to different parts of the brain.
  • It illustrates the use of an instrumental case studyto study something that cannot be manipulated in a lab experiment
  • However, it illustrates the generalisability problems in case studies, because H.M. was a one-off case


Henry Gustav Molaison has been called the most important patient in the history of brain science. Henry suffered from epilepsy caused by a head injury when he was seven. As he grew up, his seizures got worse, until surgery was his only hope for relief.

The pioneering brain surgeon William Beecher Scoville proposed to remove the part of the brain that was causing the seizures. Henry agreed to the operation. In 1953, when Henry was 27, Scoville performed bilateral medial temporal lobe resection. This involved removing part of Henry’s temporal lobe, including parts of the hippocampus and amygdala.
Resection is still used today to treat epilepsy, but with the aid of lasers and detailed brain scans. Scoville didn't have these tools and wasn't even aware what the hippocampus did. Modern patients don't suffer the side-effects that H.M. did.
When Henry recovered from the surgery, he suffered from severe amnesia. He could remember his childhood: he knew his name and family and could remember the stock market crash of 1929. However, he struggled to remember the years leading up to the surgery and had gaps in his memory of the 11 years before.

Even more importantly, Henry had severe anterograde amnesia. He lost the ability to form new memories and forgot everything that happened to him in a matter of seconds.

This is how he described his condition:
like waking from a dream… every day is alone in itself - Henry Molaison
When it became clear how severe the side-effects of the surgery were, a young researcher named Brenda Milner conducted a case study on Henry Molaison and compared her findings with Dr Scoville's medical procedures and published the findings in 1957. She protected Henry's identity by referring to him as "H.M."

The case study caused a sensation and is one of the most widely-cited psychological studies ever. It changed our understanding of memory and the brain.

Milner carried on testing H.M. and published the results between 1962 and 1972, demonstrating the existence of procedural memory. Meanwhile, H.M. had become a full-time research participant, under the supervision of Suzanne Corkin at MIT, who carried on publishing studies (and, in 2013, a book about H.M. called Permanent Present Tense).

H.M. died in 2008, at the age of 82. His much-studied brain was removed and scanned using MRI. It was then sliced into 2401 pieces, each just 70 micrometres (millionths of a metre) thick, and turned into slides that would help researchers to map the brain.

After his death, H.M.'s identity was revealed to the world. He always supported the research he took part in (when it was explained to him). On one occasion he joked with Prof. Corkin:
It's a funny thing – you just live and learn. I'm living and you're learning - Henry Molaison
Fantastic animated summary of H.M.'s condition and Brenda Milner's research



To investigate the extent and nature of H.M.'s memory deficits and how they relate to his brain damage. In particular, Milner (and later, Corkin) investigated the structure of memory as revealed in H.M.'s behaviour and the function of brain structures like the hippocampus.


One adult male, H.M., aged 27 at the start of the first case study. H.M. suffered from both retrograde amnesia (loss of memories from before his brain operation) and anterograde amnesia (loss of memories after his brain operation).
In fact, in Scoville & Milner's original study, 9 of Scoville's patients were described. However, since they suffered from disorders like schizophrenia, the resection didn't remove their symptoms. H.M. was the only one with "clean" amnesia - memory loss but no other mental problems.

Brenda Milner's early tests were simple recall tasks, testing H.M.'s ability to recall events from his childhood, from his adult life before the operation and from his experiences after the operation. She also tested his short and long term memory recall. Finally, she tested his other cognitive faculties, like IQ, perception and general knowledge.
Other tests were carried out on H.M.. For example, the effect of reinforcement and punishment was investigated, to see if mild electric shocks would help H.M. to remember correct answers. Later, under the direction of Suzanne Corkin, brain scanning technology was used to improve our understanding of H.M.'s condition.

H.M. forgot all new experiences after about 30 seconds; however he remembered a lot of information from before his sixteenth birthday. His personality was consistent, he had good language skills and an above-average IQ. His perception was normal, except for his ability to identify smell, which was very poor.

H.M.loved to describe clear memories of his childhood, over and over, though he lacked a context for them (like how long ago they happened). The face he saw in the mirror surprised himself. Every time H.M. met Milner (and later, Corkin), he introduced himself as if they had never met before, and told his stories again.

H.M. had a knowledge of past events (the Wall Street Crash, World War II). H.M. could not explain where he lived, who cared for him, what he ate for his last meal, what year it was, who the president was, or even how old he was.  In 1982, he failed to recognize a picture
of himself that had been taken on his 40th birthday in 1966.

However, he did acquire some knowledge from after his operation: he knew what
an astronaut was, that someone named Kennedy was assassinated and he learned what rock
music was. He learned how to play tennis, although he could not remember being taught the skills and denied that he knew how when asked.
Attempts to test punishment with electric shocks had to be abandoned. H.M. possessed huge tolerance for electric shocks, barely noticing shocks that normal people found quite painful. He also seemed to have difficulty noticing feelings of tiredness and hunger.


Milner's qualitative data shows a clear difference between short term and long term memory. They suggest that the hippocampus plays a vital role in transforming short term memories into long term memories, because this was something H.M. (whose hippocampus had been removed in the operation) couldn't do.
H.M.'s poor ability to identify smell may be linked to the fact that the olfactory bulb - which processes smell - is located close to the hippocampus. H.M.'s poor response to pain and confusion over hunger and tiredness probably links to the damage to his amygdala, which also explains his calm response to the situation he found himself in.
Milner's quantitative data and the later qualitative data suggests a more complex structure for memory.

H.M. did not improve at the maze task because, when he figured out the correct route through the maze, he immediately forgot it. However, he got better at the star task, despite forgetting his previous attempts. Later in life, he learned to play tennis.  This suggests H.M. remembered skills even if he forgot events.

H.M. also remembered some items of general knowledge (the moon landings, the Kennedy assassination), even though he couldn't remember the events taking place.

Milner termed this sort of memory "unconscious memory", but Eron Tulving later termed it procedural memory (skills) and semantic memory (general knowledge).
Milner also tested H.M. with maze tasks. H.M. attempted to trace the correct route through the maze with his finger. Milner then tested him over and over with the same maze to see if H.M. would remember the route, even if he didn't remember having attempted the task before.
In the 1962 case study, Milner asked H.M. to copy a five-pointed star by drawing between the lines of a template. However, H.M. could only see the reflection of the star and his hand in a memory. This made the task difficult. As with the maze task, Milner asked H.M. to re-attempt the task many times, to see if he grew more skilled at the procedure even though he didn't remember doing it before.
Over 252 attempts, H.M. never showed any improvement in the maze task.

However, H.M.did show improvement in the star-tracing task, making fewer mistakes on each attempt. He started with 30 errors, dropping to 20 on his second attempt and 10 by his seventh. Moreover, he kept these skills from one day to the next, getting better and better at it: on Day 2 he started making only 25 mistakes, immediately dropping to fewer than 10; by Day 3, he was making fewer than 5 mistakes each time.



Scoville & Milner reviewed 9 patients who had undergone resection surgery, but the others were sufferers of schizophrenia and depression whose symptoms interfered with memory testing. H.M. was unusual in that he suffered from "clean" amnesia - his memory loss was his only problem. This makes him much more representative of ordinary people.

On the other hand, H.M. was a "one-off" - a unique case. Scoville never performed this surgery again and modern resection surgery is accurate enough to avoid the sort of brain damage H.M. suffered. This means we can never be sure just how "normal" H.M. really was. Because no one expected the resection to cause memory loss, no one tested H.M.'s memory before the operation.

Milner used tried-and-tested memory tests and puzzles. Most of these had been designed by other memory researchers and many of them were replicated on H.M. by later researchers like Suzanne Corkin. They all showed consistent results with H.M. - a great example of standardised procedures and test-retest reliability.
In fact, H.M.'s condition made him a great test subject. Since he never remembered having done the tests before, he never got bored of them and tackled them enthusiastically every time.
On the other hand, the case study itself is hard to replicate. Now that H.M. is dead, there may well never be a patient like him again.

The application of H.M.'s case studies for psychology has been huge. Before H.M., psychologists thought that memory was a single function that took place all across the brain. After H.M., it became clear there are different memory functions that take place in different parts of the brain.
By revealing the importance of brain structures like the hippocampus, H.M.'s case studies led to safer and more successful brain surgery techniques.

However, some critics claim that H.M.'s case, being so famous, has led to too much attention being paid to the hippocampus and not enough to other regions of the brain linked to memory. Vann & Aggleton (2004) report the case of B.J. who had a snooker cue forced up his nose, damaging the base of his brain and causing amnesia, although his hippocampus was undamaged.

Brenda Milner visited H.M. at his family home and tested him there. Although her memory tests were quite artificial, she also made observations about H.M.'s behaviour and habits - such as his watching old movies on TV without remembering having seen them before - which backed up the test results.

Later, H.M. went to be cared for by Suzannne Corkin's team at Massachusetts Institute of Technology (MIT). This might have been a less natural environment for H.M., but, given his condition, he never noticed. In effect, all environments became strange for H.M., who couldn't even recognise himself in the mirror, let alone realise he was living in a strange place.

The strength of H.M. as a case study is the validity of his condition: H.M. suffered from "pure" or "clean" amnesia with few other symptoms and was willing to work with researchers to understand the brain.

H.M. consented to his surgery in 1953. No one warned him about the memory side-effects because no one understood the function of the hippocampus at that time.

H.M. continued to consent to taking part in research for the rest of his life - every time it was explained to him, which was many times, daily, for over 50 years!

Critics point out that H.M. was in no position to withhold his consent - he was entirely dependent on the researchers for his care and did not understand his situation. It could be argued that H.M. was a "human guinea pig" whose sad condition was exploited by researchers.

However, the research followed the principle of Respect. Up until his death, H.M.'s real identity was kept secret to protect his privacy. Only 100 researchers were ever granted access to H.M., out of respect for his dignity. What's more, the research could be justified in terms of Social Responsibility.

Suzanne Corkin reflects on H.M.'s life in this way:
[H.M. was] an engaging, docile man, with a keen sense of humour, who knew he had a poor memory and accepted his fate … and hoped that research into his condition would help others live better lives - Suzanne Corkin
H.M. himself reflected on his brain damage and the research on him like this:
What [Dr Scoville] learned about me helped others, and I’m glad about that - Henry Molaison


Assess how case studies of H.M. have contributed to our understanding of memory. (8 marks)
  • A 8-mark “evaluate” question awards 4 marks for AO1 (Describe) and 4 marks for AO3 (Evaluate). You need a conclusion for top band (7-8) marks.

H.M. suffered from life-threatening epilepsy and in 1953 Dr Scoville cured this by removing H.M.'s hippocampus.
As a result, H.M. suffered from retrograde amnesia (remembering only his life before age 16 with clarity) and anterograde amnesia (forgetting all his new experiences within 30 seconds).
H.M. was visited by Brenda Milner who conducted tests on him like the star-drawing test and published several case studies on his condition in the '50s and '60s.
Milner showed that, without a hippocampus, H.M. could not create new episodic memories but he could still learn semantic memories (like the moon landings) and procedural memories (like the star test or playing tennis).

Before H.M., psychologists did not appreciate that memory was made up of different functions that took place in different parts of the brain, particularly the hippocampus.
Milner's research on H.M. led to the development of the Multi Store Model and to Tulving's concepts of procedural and semantic memory as well as episodic memory.
Some researchers argue H.M.'s fame has led to too much focus on the hippocampus: the case of B.J. whose amnesia was brought on by a snooker cue up the nose suggests other areas of the brain are important too.
Now that H.M. is dead, his brain has been scanned and sliced into slides only 70 microns thick in order to help researchers understand the structure of the brain in more detail.

H.M.'s value to researchers comes from his being a "clean" or "pure" amnesia sufferer who had very specific brain damage and no mental disorders other than memory loss. This has made him very valuable as a research subject.

  • Notice that for a 8-mark answer you don’t have to include everything on H.M.. I haven’t mentioned the maze tests or details on how the star-drawing test worked. I haven't evaluated the studies in terms of ethics. But I have tried to make the two halves – Description and Evaluation – evenly balanced.

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