Mechanism of Discerning Similarities in Psychiatric Diagnoses

doi:10.4236/ce.2013.46A001

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Creative Education

2013. Vol.4, No.6A, 1-8

Published Online June 2013 in SciRes (http://www.scirp.org/journal/ce) http://dx.doi.org/10.4236/ce.2013.46A001

Mechanism of Discerning Similarities in Psychiatric Diagnoses

Haim Eshach

Ben Gurion University of t he Ne ge v , Beer Sheva, Israel

Email: [email protected]

Received April 23rd, 20 1 3; revised May 23rd, 2013; accepted May 3 1st, 2013

tion License, which permits unrestr ic ted u se, distribution, and r eproduction in any medium, provided the original

work is properly cited.

Psychiatrists use similarities to make diagnoses in situations where rules are insufficient. The purpose of

this study was to examine the criteria psychiatrists use to determine similarity between cases of personal-

ity disorder. Psychiatrists were provided with cases and were interviewed according to Kelly’s method.

Cognitive science theories were used to explain the criteria identified. Results indicated that similarity de-

cisions include idiosyncratic criteria. These results add to the current understanding of medical prob-

lem-solving processes and have implications for medical education.

Keywords: Similarity; Psychiatric Diagnoses; Medical Education

Introduction

Clinical reasoning, a highly complex phenomenon (Higgs &

Jones, 1995), is defined as the thinking processes occurring

while dealing with a clinical case (Boshuizen & Schmidt, 1995).

The problems that patients present can be confusing and con-

tradictory, characterized by imperfect, inconsistent, or even

inaccurate information (Kassirer & Kopelman, 1991; Eshach &

Bitterman, 2002). In addition, medical problems are often

poorly defined (Barrows & Feltovich, 1987). Not only is much

irrelevant information present, but relevant information about

the case is often missing and does not become apparent until

after problem solving has begun (Voss & Post, 1988). In such

cases, it is difficult to specify the state from which one can start,

to identify the medical interventions that might be applicable,

or even to recognize when the goal has been achieved. In other

words, many medical problems are ill-defined. Moreover, in

many situations, the deterministic mechanisms that account for

the medical problems are not completely understood (Williams,

1992). In other words, many medical domains are “ill-domain

theories”. Despite the uncertainty and variation that character-

ize physicians’ work they have to diagnose and treat such ill-

nesses. In order to do this, physicians use different types of

reasoning e.g. rule-based reasoning and similarity-based rea-

soning. In the following paragraphs I first explain why person-

ality disorder realm was chosen for the purpose of this study.

Secondly I explain why rule-based reasoning cannot alone ex-

plain the variety of medical decision making processes. Third, I

argue that similarity decisions may be effective to solve

ill-defined problems in ill domains. I then suggest to study the

factors according which similarities are made.

Personality Disorders as the Focus of the Study

The etiology and pathogenesis of most personality disorders

are not known; psychiatrists therefore tend to resort to phe-

nomenological, descriptive criteria in the diagnosis of these

conditions. Many of the definitions provided in the Diagnostic

and Statistical Manual of Mental Disorders (DSM-IV) (Ameri-

can Psychiatric Association, 1994) are set up in a format

whereby an individual must have a subset of several features in

order to be diagnosed. Thus, for the nine DSM-IV diagnostic

features of borderline personality, for instance, at least five of

which are required for diagnosis, there are 256 different criteria

combinations that can result in this diagnosis (Morey, 1998). In

addition, the study of personality disorder leads into areas in

which the distinction between health and sickness is inherently

ambiguous and is potentially biased by societal norms and per-

sonal values. To a large extent, whether persons are considered

to have a personality disorder depends on whether their person-

ality traits are noxious to the society in which they live and, in

particular, to the persons with whom they most frequently in-

teract (Kaplan & Sadock, 1996). This means that formal diag-

nostic systems such as the DSM-IV, which define rules to cate-

gorize discrete pathological entities, are not sufficient and can-

not always lead to the diagnosis of the personality disorder.

Despite the uncertainty and variation that characterize personal-

ity disorders, psychiatrists have to diagnose and treat them. It is

my assumption that perceiving similarities, an ability that is one

of the most fundamental aspects of human cognition (Vos-

niadou & Ortony, 1989), is used by psychiatrists in the diag-

nostic and treating of personality disorders.

Domain Rule -Based Rea soning

In order to better understand this phenomenon one should

first distinguish between domain rule-based reasoning (RBR)

and the use of a rule or rules in problem solving. The former is

identified as the process of drawing conclusions by chaining

together generalized rules, starting from scratch (Leake, 1996).

The latter, on the other hand does not require starting from

scratch nor does it require chaining together rules. For the pur-

pose of this study I will focus on RBR processes. RBR models

are rooted in the philosophical belief that humans are rational

H. ESHACH

beings and that the laws of logic are the laws of thoughts (Ey-

senck & Keane, 1995). According to Kolodner (1993), although

some rules are very specific, the goal is to formulate rules that

are generally applicable. An important advantage of rules is the

economy of storage they allow. But general knowledge has the

problem of applicability (Mostow, 1983), i.e., the bringing of

some general piece of knowledge to a particular situation.

When rules are expressed too abstractly, the terms tend to be

unintelligible to the novice and to mean a variety of specific

things to the expert. Also, in ill-defined domains, the rules do

not encompass all the situations they are asked or assumed to

cover, admit tacit exceptions, or can be contradicted and an-

nulled by other rules (Rissland & Skalak, 1991).

Limited mental capacity is another reason why RBR alone

cannot explain the human problem-solving processes. RBR,

which requires that the problem solver take into account all the

domain rules, is not capable of doing that in real-life situations

(BarOn, 1993), as the number of rules required for solving a

problem may be unmanageably large (Leake, 1996). Similarity

based reasoning offers an attractive way out of these difficulties.

Rather than having to patch up abstract rules with endless

sub-rules, according to similarity-based models of reasoning,

problem solving depend, especially while working in ill-do-

mains theories and ill problems, on the ability to identify the

most relevant bodies of knowledge that already exist in mem-

ory so that this knowledge can be used as a starting point for

encounter the novel situation. I do not focus on a particular

model such as the prototype models, the exampler models,

connectionist models and the probabilistic models, but rather

relate to the similarities underlying all these kinds of models.

Similarity

Rumelhart (1989) claims that most everyday reasoning

probably involves assimilating the novel problem to other

situations in which the solutions are known—that is, reasoning

by similarity. He further suggests that the reason for the impor-

tant role of reasoning by similarity is the essential human abil-

ity for pattern matching. “We seem to be able to ‘settle’ quickly

on interpretation of an input pattern. This is an ability that is

central to perceiving, remembering, comprehending, and rea-

soning by similarity. Our ability to pattern—much is probably

not something that sets humans apart from other animals but is

probably the essential component to most cognitive behavior”

(Rumelhart, 1989: p. 300). Support for similarity processes can

be found in cognitive neurosciences research. This indicates

that different neural circuits are involved when people catego-

rize items on the basis of a rule, as compared with when they

categorize the same items on the basis of similarity (Kolodny,

1994).

The term “similarity”, which typically refers to the outcome

of comparison among entities, can be regarded as a form of

judgment—what people say when asked to compare different

entities (Sloman & Rips, 1998). Goodman (1972) argues that

claiming that two things are similar is uninformative until we

specify in what respect they are similar. According to Gold-

stone (1994) people do not usually compare objects only in a

single respect such as “size” but along multiple dimensions

such as size, color, shape, etc. Kelly (1955a) claims that two

things are “similar”, “alike”, or “identical” obviously means

that they are alike in some particular way or ways, but, of

course, never in every way. Their alikeness makes no sense

unless it also serves to distinguish them from certain other

things. Thus, according to Kelly, likeness always implies a

difference. At the same time, the way in which two things are

different must, if it is to make any sense at all, be the way in

which at least one of them is like a third thing.

Aims

This study focused on understanding the process of how pro-

fessionals find similarities between cases. The following ques-

tions are therefore addressed:

1) What are the differences between the various diagnoses

given by psychiatrists to given cases?

2) What are the criteria that psychiatrists use to decide on

similarities between cases?

Method

Participants

Nine psychiatrists at different levels of medical experience

were chosen for this study.

Participant 1: 20 years’ experience; Participant 2: 6 years’

experience; Participant 3: 7 years’ experience; Participant 4:

10 years’ experience; Participant 5: 5 years’ experience; Par-

ticipant 6: 2 years’ experience; Participant 7: 4 years’ experi-

ence; Participant 8: 5 years’ experience; Participant 9: 5 years’

experience.

Procedure

1) Nine patients diagnosed as suffering from personality dis-

orders according to DSM-IV criteria who agreed to participate

in the study were identified. The following list describes the

diagnosis given by the department in which the patients were

treated:

a) Narcissistic personality disorder with dependent traits;

b) Borderline personality disorder with narcissistic traits;

c) Narcissistic personality disorder;

d) Borderline personality disorder;

e) Narcissistic personality disorder;

f) Dependent personality disorder;

g) Narcissistic personality with obsessive traits;

h) Obsessive-compulsive disorder;

i) Borderline personality with narcissistic traits.

A psychiatrist who was very familiar with all the cases con-

ducted an introductory interview with each one of the patients.

This enabled him to extract the maximum and most pertinent

information from each case. The interviews lasted between 20

and 25 minutes. The interviews were videotaped and tran-

scribed. Transcripts of each interview were used as cases in-

troduced to the participants.

2) The transcripts of the nine cases were presented to each of

the participants, all of whom were unfamiliar with the nine

patients. The participants were each instructed to do the fol-

lowing1:

a) Diagnose each case. The participants were asked to think

aloud while diagnosing the cases. These sessions were tape-

recorded, and verbatim transcripts were produced.

b) Group cases according to important similarities of their

own choice.

1This idea is the basis for Kelly’s (1955) repertory test, from which we have

drawn the interviews described in the method for the current research.

H. ESHACH

c) Consider predefined sets of three cases and describe how

two of the three cases are alike and how they are different from

the third; in other words, to decide on a criterion for the simi-

larity between two cases among the three presented in the set.

d) Subsequently, to indicate which of the remaining six cases

matched the chosen criteria.

For c) and d), Table 1 was used as a template for the inter-

view.

The author interviewed each participant, each interview last-

ing between 5 and 6 hours. Since the interviews were so long,

they were divided into two parts of between 2.5 and 3 hours

each, conducted on two successive days. In this way the par-

ticipants remembered the cases, and it took very little time for

them to go over the cases again. After piloting the interview

method, it became clear that 14 sets were optimum for inter-

view acceptability by the participants.

This method required the identification of the two most

similar cases of a set of three and enabled us to identify the

variety of criteria used to decide on similarities between cases.

For instance, when participant 4 was introduced to set 4 (cases

2, 5, and 8), she identified cases 2 and 8 as similar. She ex-

plained, “In both cases they try to solve an internal conflict.

The crisis starts early in life. Case 5 is not trying to solve an

internal conflict”. When the participant was presented with set

5, she again identified cases 2 and 8 as similar. She explained

that both cases had “organized life, while case 3 had chaotic

life”. For the same pair of cases she used different criteria.

Analysis

The interview audiotapes were transcribed verbatim, and in-

ductive analysis, in which patterns, themes, and categories of

Table 1.

Interview template.

Set

number Set of three

casesa Similar

casesb Expl an atio n c Other similar

casesd

1 2 3 4

2 2 3 5

3 3 5 7

4 2 5 8

5 2 3 8

6 1 6 8

7 1 3 5

8 4 5 9

9 2 4 5

10 2 6 8

11 5 7 9

12 2 4 9

13 4 5 8

14 3 7 9

Note: aPredefined sets of three cases each. bThose two cases that the participant

identified as similar. cReasons that the participant gave in answer to “in what respect

are the cases similar?” dThose cases of the six remaining that the participant

identified as similar to the earlier two cases already chosen for their similarity.

analysis derived from the data (Patton, 1990), was employed.

The analysis process contained the following:

All the transcripts were repeatedly read to formulate tentative

understanding.

a) In subsequent readings, an attempt to find confirmation or

disconfirmation to the tentative understanding of the phenom-

ena on the tape was made.

b) Through this process of constant comparison (Strauss,

1987), initial categories for the differences between the diag-

noses were established.

c) In the same manner, criteria used to decide similarities

were identified, and initial categories for the criteria were rec-

ognized.

d) The data were repeatedly reread, and the initial categories

were revised as a result of several rounds of discussion verifi-

cation methodology (Strauss, 1987).

e) This sharing and critiquing also assisted in the process of

progressive subjectivity (Guba & Lincoln, 1989).

Results and Discussion

Results Regarding the Diagnoses

1) Differences between the diagnoses given by the nine par-

ticipants were found. Table 2 summarizes the diagnoses that

were given to each case by the participants.

2) Four classes of difference were identified. See Table 3.

3) The data indicated that the participants focused on defer-

ent details in each case. The following citations of three par-

ticipants (2, 6, and 9) while diagnosing the same case (6) dem-

onstrate this phenomenon:

Participant 2: “He [the patient] describes his life through his

functional ability and less through interrelationships with others.

Despite not being uncomfortable around people, he was never

close to them. There is a personality disorder on the basis of

creating relationships with other people … In this case schizoid

personality disorder seems to me as the one he suffers from …”

Participant 9: “The more reasonable possibility seems to me

that he wants the insurance money. He does not describe psy-

chiatric details, but things that anyone can describe. He contin-

ues to describe details from the accident and what happened

due to the accident. He doesn’t cooperate on discussing details

after the accident. He does not remember how he was as a high

school student, which indicates memory disorder, which seems

unreasonable in this case.”

Participant 6: “His work provided him with high self-esteem.

Everyone related to him in a special way; they liked him. He

was always the best. In this case I would say that he is a narcis-

sistic personality.”

Each participant focused on other details in the same case.

Participant 2 focused on the nature of the interpersonal relations

of the patient (case). Participant 9 focused on the accident de-

tails. Participant 6 focused on details describing the patient’s

workplace. This might be one explanation for the differences

between the diagnoses given by the participants.

Results Reg arding Criteria Used to Dec ide on

Similarity

1) Four categories of the criteria used by the participants to

decide similarities between cases were identified:

a) Diagnosis as it appears in the literature (e.g., “cases 2 and

3 are similar because they are bonarcissists”). Narcissist is a th

H. ESHACH

Table 2.

Diagnosis given to each case by the participants.

Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 Case 9

Narcissistic

personality

with

dependent

traits

Borderline

personality with

narcissistic traits

Narcissistic

personality Borderline

personality Narcissistic

personality Dependent

traits

Narcissistic

personality and

obsessive traits

Compulsive

personality

Borderline

personality and

narcissistic

personality

Narcissistic

traits with

dependent

traits

Narcissistic

personality

Borderline

personality

and

narcissistic

personality

Borderline

personality

with

narcissistic

traits

Narcissistic

personality Schizoid

Narcissistic per-

sonality, obsessive

traits, and de-

pendent traits

Compulsive

personality

Borderline

personality and

narcissistic

personality

Narcissistic

personality

with

dependent

traits

Borderline

personality with

narcissistic traits

Borderline

personality

with

histrionic

traits and

dependent

traits

Borderline

personality Narcissistic

personality Dependent

personality Narcissistic

personality Compulsive

personality

Borderline

personality and

histrionic

personality

Narcissistic

traits with

dependent

traits

No personality

disorder

personality

disorder

Borderline

personality

with

obsessive

traits

personality

disorder

personality

disorder

No personality

disorder Compulsive

personality

Borderline

personality and

narcissistic

personality

Narcissistic

traits with

dependent

personality

Narcissistic

personality Narcissistic

personality Borderline

personality

Obsessive

personality and

narcissistic traits

personality

disorder

Narcissistic

personality,

obsessive

personality, and

dependent

personality

Compulsive

personality

Narcissistic

personality and

histrionic

personality

Dependent

personality

with

histrionic

traits

Borderline

personality with

narcissistic traits

Narcissistic

personality Borderline

personality

Narcissistic

personality and

obsessive

personality

Narcissistic

personality

Narcissistic

personality,

obsessive traits,

and histrionic

traits

Compulsive

personality

with paranoid

traits

Borderline

personality and

histrionic

personality

Histrionic

personality

with

dependent

traits

Borderline

personality

Histrionic

traits and

borderline

traits

Borderline

personality

with

obsessive

traits

personality

disorder

Dependent

personality Narcissistic

personality

Borderline

personality and

histrionic

personality

Narcissistic

personality

and

dependent

personality

Borderline

personality and

narcissistic

personality

disorder

Borderline

personality

with

obsessive

traits

personality

disorder

personality

disorder Narcissistic traits Compulsive

Personality

Narcissistic

personality,

histrionic

ersonality, and

borderline traits

Narcissistic

traits with

dependence

personality

No personality

disorder Borderline

personality Borderline

personality Narcissistic

personality

disorder

Narcissistic

personality Compulsive

Personality Histrionic traits

personality disorder that can be found in the literature.

b) Clusters of disorders (e.g., “cases 2 and 5 are similar be-

cause they present the same cluster, while case 8 belongs to a

different cluste r”).

c) Severity of the personality disorder (e.g., “cases 2 and 4

are more serious cases of personality disorder than case 5”).

d) Personal criteria (e.g. “I don’t l ike either of them …”; “they

are both immature”; “in both cases the problem began after

their marriage”; “in both cases they had the same style of life”).

2) The participants used different criteria to decide on simi-

larities between the same sets of cases.

3) The criteria which psychiatrists used to explain similarities

could be divided into two categories: formal/nonformal criteria

and subtle/general criteria.

a. Formal/nonformal criteria. For the purpose of this study,

formal criteria were those criteria found in the literature that the

subjects used for their decisions on the similarity between cases.

These criteria included personality disorder categories; the

categorization of traits; and rules describing the personality

disorder, the traits and the axis. Examples from the interviews

are as follows:

“They both have a borderline personality disorder, while

the other case is narcissistic.”

“In this pair, axis 1 is dominant, while in the other case

axis 2 is dominant.”

“There is meaning to the relationship between the patient

and her psychiatrist.”

H. ESHACH

Table 3.

Classes of differences be t w een diagnoses.

Classes of d ifferences

between diagnoses

Identification of personality

disorders In four cases (45%), at le ast two participants did not identify a personal ity disorder.

Different diagnoses of

personality disorders

Psychiatrists diagnosed differently the same cases. Examples:

1) Case 3 was diagnosed by three participants (33%) as narcissistic, whil e three other participants id entified the case

as borderline personality d isorder.

2) Diagnoses for case 6:

a) Four participa nts did not identify any personality dis order.

b) One participant identified dependent traits.

c) Two participants identified dependent personality.

d) One participant identified schizoid personality disorder.

e) One participant identified narcissistic personality disorder.

Severity of personality

disorder In some cases there were differences in the severity attributed to the disorder. While some particip ants identify

personality disorders in a case, others identified only personality disorder traits.

Number of personality disorders

attributed to each patient

For instance, in case 7, four participants (45%) identifie d only narcissistic personality disorder. One participant

identified narc issistic personality disorder with obsessive-compul sive disorder. Three participants identified

narcissistic, dependent, and obsessive-compulsi v e personal ity disorders.

Nonformal criteria were those that were not found in the lit-

erature or occurred when personal meaning was given to formal

criteria. Examples from the interviews are:

“This is his first admission in the hospital.”

“They didn’t achieve anything in life.”

“Only her economic status is important for her.”

“Problems began after marriage.”

“He is cold. Doesn’t express feelings.”

“They both make me nervous. I don’t like them.”

From these results we can conclude that psychiatrists use

both formal and nonformal criteria to determine similarity be-

tween cases. In some cases the nonformal criteria had more

weight in making the similarity decisions, while in other cases

it carried less weight. The following examples will clarify this

point:

Example 1: When participant 6 was provided with cases 2, 5,

and 8, he identified cases 5 and 8 as similar because “both have

a gray personality and style, while case 2 is much more color-

ful.” However, his main diagnosis for both cases 2 and 5 was

narcissistic personality disorder, while he diagnosed case 8 as

obsessive-compulsive disorder. Use of DSM-IV diagnostic cri-

teria would lead to the decision that cases 2 and 5 are similar.

Example 2: When participant 3 was provided with cases 2, 3,

and 5, she identified cases 3 and 5 as similar because “both

have a need for attention. Case 2 also needs attention, but he is

colder; he doesn’t express affection”. The basis for similarity

was nonformal, by an idiosyncratic criterion. Moreover, she

diagnosed case 2 as borderline and narcissistic personality dis-

orders, case 3 as borderline and dependent personality disorders,

and case 5 as narcissistic. Therefore, if the DSM-IV criteria had

been the basis for her similarity decisions, it would be unlikely

that she would have chosen cases 3 and 5, to whom she in fact

gave different diagnoses. It would be more reasonable to de-

termine cases 2 and 3 as similar, since they both suffered from

borderline personality disorder. This demonstrates that idiosyn-

cratic/nonformal criteria were more heavily weighted in this

comparison.

b. General/subtle criteria. The results indicated that the par-

ticipants used both general and subtle criteria. General criteria

are those that require a rough level of diagnosis. For instance,

personality disorder is a general criterion, whereas one specific

rule appearing in the DSM-IV under that personality disorder

category is a more subtle criterion. Examples from the inter-

views are:

General criteria:

“They are both borderline, while the other case is narcis-

sistic.”

“They are both from the same age range.”

“They are both women.”

Subtle criteria:

“He doesn’t need to be in relationships with others.”

“She hurt herself, feels emptiness.”

“There are extreme fluctuations in their mood.”

Another example of using subtle criteria was when the same

diagnoses were given to three cases, but one was determined to

be dissimilar to the other two, e.g., because “she is more sta-

ble”. Here the severity attributed to the case required subtle

criteria.

We therefore found no preference for the use of general over

subtle criteria.

4) It was found that heuristics impacted on the criteria by

which the participants determined similarities.

Heuristics are mental shortcuts, “rules of thumb”, which do

not guarantee a solution to the problem, but more often than not

do succeed and save a lot of time and effort in the process (Ey-

senck & Keane, 1995). Heuristics, which are commonly used in

decision making, may lead to faulty reasoning or conclusions

(Elstein, 1999). Representativeness and availability are exam-

ples of such heuristics (Kahneman, Slovic, & Tversky, 1982).

The impact of “availability” heuristic

There are situations in which people are prone to overesti-

mate the frequencies of easily recalled events (Elstein, 1999;

Kahneman, Slovic, & Tversky, 1982). This judgmental heuris-

tic is calle d av ailability . E xa mpl e from t h e interviews:

While dealing with case 2, participant 9 interpreted the de-

tails of that case and made the diagnosis in a very unique way.

She was the only participant who diagnosed this case as psy-

chotic, and she argued that he did not suffer from a personality

disorder. Here are some justifications that she gave:

H. ESHACH

“He has thoughts that he is a prophet, that he has fire in

his bones. He always murmurs. He believes that if he does

something, he will prevent things from happening. His

ideas are not coherent … It seems that the things in the

interview are fragments, and the only connection between

the different parts of the interview is that they are succes-

sive…It seems as if he is suffering from schizophrenia,

though it is early to decide.”

It was found that a special program dealing with many psy-

chotic cases, in which one of the participants had participated

for eight months prior to this study, had an impact on the diag-

noses she gave and the similarity criteria she used. The cases

the subject had dealt with prior to this study were easily

brought to mind. As a result, her decisions were significantly

based on these cases.

The impact of the “representativeness” heuristic

When deciding on the probability that object A belongs to

class B, people typically rely on the “representativeness” heu-

ristic, in which probabilities are evaluated by the degree to

which A is representative of B, that is, by the degree to which

A resembles B (Kahneman, Slovic, & Tversky, 1982).

For example, when participant 3 was provided with cases 3,

5, and 7, she identified cases 5 and 7 as similar because “…

nurse and physician [case 5 was a physician and case 7 was a

nurse], this combination is achieving, persistence in work, high

functional lev el, consistent …”

Participant 3 had a mental picture of people who work in

medical occupations. Therefore, it might have been that she felt

a high probability that cases 5 and 7 belonged to this group.

This heuristic therefore influenced her decisions on similarity.

5) Similarity process involves the search for local similari-

ties.

While deciding on similarities between cases, psychiatrists

focus only on part of the details of each case. The following

example clarifies this point:

When provided with the cases 3, 5, and 7, participant 6 de-

cided that cases “5 and 7 are similar because they are both

narcissistic. There is something obsessive in both cases. The re

is a failure in relating to their kids”. When provided with the

cases 5, 7, and 9, the participant determined that 7 and 9 are

similar because they are both “extravagant, dramatic, and deal-

ing with emotions” (as opposed to 5 and 7). In another situation

the participant noted “case 9 is similar to cases 2 and 4 because

in all those cases there are changes in mood, which are ex-

pressed in their willingness to die. In both cases they harm

themselves”. According to this participant those are not charac-

teristics of case 7. For each comparison the participant focused

on different characteristics of each case.

6) In 85% of the three-case sets, more than half of the sub-

jects chose the same two cases as similar. Moreove r, in 65% of

the case sets, two thirds of the participants chose the same pair

of cases. However, the explanations given to make these

choices tended to be different, i.e., subjects tended to identify

the same cases as similar, but gave different explanations.

Discussion

Use of Idiosyncratic Personal Knowledge

This research aimed at identifying the criteria by which psy-

chiatrists decide similarities between personality disorders.

Findings indicate that criteria consisted of nonformal and per-

sonal knowledge. Moreover, sometimes these nonformal/per-

sonal criteria contradicted the diagnoses they identified. This

result lends support to the important role of personal knowledge

in reasoning which challenge the RBR models. RBR models

emphasize on the importance of abstract information in prob-

lem solving and ignore the value of knowledge of a specific

event and specific experiences (Cohen, 1996). The personal

knowledge point of view, on the other hand, sees in knowledge

of specific episodes a key to successful problem solving. Per-

sonal knowledge is defined as the unique frame of reference

and knowledge of self, is central to the individual’s sense of

self (Higgs & Titchen, 1995), and is a result of the individual’s

personal experiences (Butt, Raymond, & Yamaguishi, 1982).

Much of the knowledge a practitioner uses in problem solving

and making clinical judgments is tacit and individual (Polanyi,

1958; Carroll, 1988). In recent years, there has been increasing

concern about the growing gap between research-based knowl-

edge taught in professional schools and the practical knowledge

and actual competencies required of practitioners in the field

(Schon, 1987). The author argues that in order to deal with the

crisis in professional knowledge, we need to recognize that

outstanding practitioners do not have more professional

knowledge, but more “wisdom”, “talent”, “intuition”, or “art-

istry”. By finding those personal criteria by which the psychia-

trists in this study identified similarities may contribute to de-

creasing the gap that Schon warn us from.

Local-Based Similarities Decisions

Other result of this study is that psychiatrists’ decisions re-

garding similarities between cases were based only on part of

the details of each case. This result was also found in their di-

agnoses processes. Psychiatrists focused on only part of the

evidence and did not take into consideration all the information

described in those cases. It is my understanding that they

searched for local coherence rather than a global coherence. An

underlining idea of RBR is that the problem solver, by chaining

together all the relevant domain’s rules, and therefore consider

all the information, is looking for global rather than local co-

herence.

Use of Heuristics

It was found that heuristics impacted on the criteria by which

the participants determined similarities. Both representativeness

and availability heuristic are similar-based as it depends on a

memory retrieval process that in turn depends on the similarity

between an encoded event and retrieval cues (Sloman & Rips,

1998). Thus, it is not surprising that it characterize the psychia-

trists who were confronted with a similarity task.

In 85% of the three-case sets, more than half of the subjects

chose the same two cases as similar. Moreover, in 65% of the

case sets, two thirds of the participants chose the same pair of

cases. However, the explanations given to make these choices

tended to be different, i.e., subjects tended to identify the same

cases as similar, but gave different explanations.

Application to Teaching

One problem of today’s teaching is the growing gap between

research-based knowledge and actual competencies required of

practitioners in the field (Eshach & Bitterman, 2002). Psychia-

trists are not always aware of their own personal knowledge

H. ESHACH

and therefore are not always aware of their own as well as of

other psychiatrists’ criteria. These primary criteria have an

impact on decision-making processes, which in most cases are

based on similarity decisions. In addition, CBR might lead to

faulty decisions. For instance, one might be tempted to use an

old case blindly, relying on previous experience without vali-

dating it in the new situation (Kolodner, 1993). One strategy to

minimize such a cognitive bias is to call these processes to the

attention of the physician and medical educator, in the hope that

when people are aware of these tendencies, they will take steps

to overcome them. Therefore, educators should take such proc-

esses into account when they design learning environments.

The present study provides many examples of criteria used in

the comparison process and thus might be useful as a teaching

aid. The results of this research may assist psychiatrists to be

aware of their own and others’ idiosyncratic c r iteria. Thi s might

also decrease the gap between book knowledge and the per-

sonal/practical experience of physicians, a concern that was

expressed by Schon (1987). In other words, researchers should

make efforts to make the implicit personal/practical experience

of physicians more explicit. Educators, on their turn, should

“use” explicit teaching—which refers to teaching that focuses

on explicit awareness (mediated by verbal interactions) of types

of cognitive procedures (i.e. strategies) being used in specific

instances (Zohar & Peled, 2007; Zohar & Ben David, 2008)—

to teach those, yet, tacit personal cognitive procedures. This

research could be expanded into other domains that rely on

similarity diagnosis.

Acknowledgements

The author would like to thank the psychiatrists who partici-

pated in the study and Miss Ruth Singer for editing the manu-

script.

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