Encyclopedia of Psychology and Law

Given the centrality of amnesia to DID, evidence of

inter-identity amnesia is essential to a diagnosis.

Caution is warranted when interpreting self-reported

symptoms of amnesia, however, as research using

objective measures of memory reveals an inconsistent

picture that does not consistently corroborate the sub-

jective symptoms reported by patients. Studies that

have examined memory transfer across identities have

provided mixed results, typically finding that some

memories are shared between reportedly amnesic iden-

tities while other memories are not. It has been pro-

posed that these differences in memory transfer depend

on whether the memories are explicit versus implicit.

Explicit memory tests require conscious recollection

and typically produce amnesia between identities. For

example, an amnesic identity may deny any memory of

words presented to another identity when asked to

recall them. In contrast, implicit memory tasks rely on

the premise that prior experiences can influence subse-

quent behavior independent of conscious awareness—

such tasks often show memory transfer. Although the

amnesic identity may claim to not recognize the words,

given an implicit test, such as a word-stem completion

task, he or she may perform in a manner that suggests

memory of the words on some level, typically assumed

to be implicit and unconscious.

This pattern of amnesia on explicit but not implicit

tasks is not unlike that found in organic amnesia.

This pattern has alternatively been interpreted as a

response to situational expectations, where individu-

als modify their response patterns in conformance

with their expectations about how a person with inter-

identity amnesia should respond. Explicit memory

tests, unlike implicit tests, are typically obvious

assessments of memory, and amnesic responding on

explicit tests could result from motivated compliance

with expectations. Implicit memory tests, in contrast,

tend to be less transparent measures of memory and

are less susceptible to manipulation.

Given the inconsistent findings of memory transfer,

and also the controversy surrounding the disorder,

inter-identity amnesia should ideally be verified by

objective tests of inter-identity amnesia that do not

rely solely on self-report. Some investigators have

attempted to objectively assess memory by using psy-

chophysiological measures such as brain electrical

recordings or by creating paradigms where amnesia is

difficult to simulate. These methods have typically

demonstrated that memories transfer across identities

despite self-reports of amnesia. Moreover, one study

has suggested that this memory transfer is conscious

and explicit. Therefore, although a phenomenological

experience of memory loss may be reported by DID

patients, this amnesia cannot always be verified by

objective memory tests. Given the centrality of inter-

identity amnesia to a DID diagnosis and the current

reliance on uncorroborated self-report measures,

increasing importance needs to be placed on using

objective tests of memory to make an accurate diagno-

sis of DID.

The Controversy

Controversy surrounds DID, as many skeptics question

the validity of the disorder. Research on the properties

of inter-identity amnesia has led to conflicting find-

ings, as detailed above. In addition, critics of the disor-

der highlight the many changes that have occurred in

prevalence rates and symptom presentation over time.

Historically, DID has been an infrequently diagnosed

disorder, with only a handful of cases being reported

until the 1900s. However, rates of diagnosis skyrock-

eted in the 1980s, with prevalence rates numbering in

the thousands. DID was popularized in the media

around this same time by movies such as The Three

Faces of Eveand Sybil.It has been suggested that this

exponential increase in diagnoses is mostly circum-

scribed to specific cultures such as North America,

with the majority of diagnoses believed to be attribut-

able to a small percentage of psychologists.

In addition to the increasing prevalence rates, the

nature of symptoms has evolved. Earlier DID patients

commonly reported only a few identities and often

needed a period of transient sleep to switch between

identities. In contrast, present-day DID patients typi-

cally report approximately 15 alters and the ability to

voluntarily switch among identities. These diagnostic,

cultural, and symptomatological inconsistencies have

incited an ongoing debate about the validity of

reported symptoms, resulting in two competing etio-

logical interpretations.

Perspectives on Causal Mechanisms

Two perspectives dominate the debate on the cause of

DID. The posttraumatic interpretation of DID, also

termed the disease model, conceptualizes the disorder

as a posttraumatic condition resulting from childhood

abuse, as the majority of DID patients report a history

of child abuse. This perspective suggests that the

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