Evaluating the Credibility of Statements Given by Persons with Intellectual Disability

Abstract

The objective of this study was to analyze the features that distinguish statements given by actual and simulated victims with mild to moderate intellectual disability, using the credibility analysis procedure known as Reality Monitoring (RM). Two evaluators trained in credibility analysis procedures using content criteria evaluated 13 true statements and 16 false statements. The results obtained show that there is little difference between the two types of statements when analyzed on the basis of content criteria using the RM procedure. The only criteria that proved to be significant for discriminating between the two types of statements were the amount of detail and the length of spontaneous statements obtained through free recall. None of the phenomenological characteristics studied turned out to be significant for discriminating between actual and simulated victims. Graphic representation using high-dimensional visualization (HDV) with all criteria taken into consideration shows that the two types of statements are quite heterogeneous. Cluster analysis can group cases with a 68.75% chance of accuracy.

Full text

anales de psicología, 2015, vol. 31, nº 1 (enero), 338-344
http://dx.doi.org/10.6018/analesps.31.1.166571
© Copyright 2015: Servicio de Publicaciones de la Universidad de Murcia. Murcia (España)
ISSN edición impresa: 0212-9728. ISSN edición web (http://revistas.um.es/analesps): 1695-2294
- 338 -
Evaluating the Credibility of Statements Given by Persons with Intellectual Disability
Antonio L. Manzanero1*, Alberto Alemany2, María Recio2, Rocío Vallet1 y Javier Aróztegui1
1 Universidad Complutense de Madrid (Spain)
2 Fundación Carmen Pardo-Valcarce (Spain)
Título: Evaluación de la credibilidad de relatos de personas con discapaci-
dad intelectual.
Resumen: El objetivo del presente trabajo consistió en analizar las caracte-
rísticas diferenciales de los relatos emitidos por víctimas reales y simuladas
con discapacidad intelectual ligera y moderada mediante el procedimiento
de análisis de credibilidad de Control de la Realidad (RM). Dos evaluadores
entrenados en los procedimientos de análisis de credibilidad mediante crite-
rios de contenido evaluaron 13 relatos verdaderos y 16 relatos falsos. Los
resultados encontrados muestran que existen pocas diferencias entre los
dos tipos de relatos. Los únicos criterios que resultan significativos para
discriminar entre los dos tipos de relatos son la cantidad de detalles y la
longitud de las declaraciones espontáneas obtenidas mediante recuerdo li-
bre. Ninguna de las características fenomenológicas examinadas resultó sig-
nificativa para discriminar entre víctimas reales y simuladas. La representa-
ción gráfica mediante visualización hiperdimensional (HDV) considerando
conjuntamente todos los criterios muestra una gran heterogeneidad entre
relatos. Un análisis de conglomerados permitió clasificar los dos tipos de re-
latos con una probabilidad de acierto del 68.75 por ciento.
Palabras clave: Evaluación de credibilidad; discapacidad intelectual; crite-
rios de contenido; testimonio; visualización hiper-dimensional.
Abstract: The objective of this study was to analyze the features that dis-
tinguish statements given by actual and simulated victims with mild to
moderate intellectual disability, using the credibility analysis procedure
known as Reality Monitoring (RM). Two evaluators trained in credibility
analysis procedures using content criteria evaluated 13 true statements and
16 false statements. The results obtained show that there is little difference
between the two types of statements when analyzed on the basis of content
criteria using the RM procedure. The only criteria that proved to be signifi-
cant for discriminating between the two types of statements were the
amount of details and the length of spontaneous statements obtained
through free recall. None of the phenomenological characteristics studied
turned out to be significant for discriminating between actual and simulat-
ed victims. Graphic representation using high-dimensional visualization
(HDV) with all criteria taken into consideration shows that the two types
of statements are quite heterogeneous. Cluster analysis can group cases
with a 68.75% chance of accuracy.
Key words: Credibility assessment; intellectual disability; content criteria;
eyewitness testimony; high-dimensional visualization.
Introduction
It has been proposed that lying would be cognitively more
complex than telling the truth (Vrij, Fisher, Mann, & Leal,
2006) because it would involve a greater demand for cogni-
tive resources (Vrij & Heaven, 1999). This is reflected in
some clichés about persons with intellectual disability that
suggest they would not be capable of making up complex
lies and, therefore, would be more believable (Bottoms,
Nysse-Carris, Harris, & Tyda, 2003). These clichés carry a
negative charge, however, that results in persons with ID be-
ing viewed as witnesses who are less credible and less capa-
ble of giving valid testimony (Henry, Ridley, Perry, & Crane,
2011; Peled, Iarocci, & Connolly, 2004; Sabsey & Doe, 1991;
Stobbs & Kebbell, 2003; Tharinger, Horton, & Millea, 1990;
Valenti-Hein & Schwartz, 1993), which makes persons with
ID more vulnerable to crimes (González, Cendra, & Man-
zanero, 2013). Peled et al. (2004) explored the perceived
credibility of young persons with ID who were required to
give testimony in a legal setting. Half of the observers were
told beforehand that the witness had moderate intellectual
disability, and the other half were told that the witness was a
person who was developmentally normal. When subsequent-
ly questioned about the credibility of the testimonies, they
stated that those testimonies given by a person with ID were
considered less credible. Henry et al. (2011) evaluated the
credibility of children with ID and of developmentally nor-
* Dirección para correspondencia [Correspondence address]:
Antonio Manzanero. Facultad de Psicología. Universidad Complutense
de Madrid. 28223 Madrid (España).
E-mail: antonio.manzanero@psi.ucm.es
mal children and found that the former, because they gave
fewer details, were less credible than the latter. They found
no correlation between the credibility evaluations and either
mental age or anxiety.
The generally lower credibility attributed to persons with
ID suggests an enormous need for a technical credibility
analysis procedure that is adapted for this type of victim so
that evaluation of their testimony is not left to intuition—
which, on most occasions, is biased (Manzanero, Quintana,
& Contreras, 2015). Such procedures do not exist at this
time, however, which means that persons with ID are often
excluded from the justice system or evaluated on the basis
of a comparison with children. This situation would be ex-
acerbated by failure to adapt legal and law enforcement pro-
cedures to the abilities of these individuals (Recio, Alemany,
& Manzanero, 2012). Such adaptations could mitigate this
serious situation, for it has been shown that, with sufficient
adaptations, persons with ID are capable of identifying an al-
leged assailant in a line-up (Manzanero, Contreras, Recio,
Alemany, & Martorell, 2012), even though they do not per-
form as well on this type of task, to begin with, as individu-
als who do not have ID (Manzanero, Recio, Alemany, &
Martorell, 2011).
Forensic psychology has proposed various procedures
for evaluating credibility through analysis of statement con-
tent (Manzanero, 2001). One of these procedures is the Re-
ality Monitoring (RM) technique (Johnson & Raye, 1981;
Johnson, Hashtroudi, & Lindsay, 1993) which is suggested
for evaluating statement credibility.
RM’s basic assumption is that statements based on
memories of actual events are qualitatively different from
statements that are not based on experience or are simply

Evaluating the Credibility of Statements Given by Persons with Intellectual Disability 339
anales de psicología, 2015, vol. 31, nº 1 (enero)
the product of fantasy, as Johnson and Raye (1981) had
shown. According to the original proposition, actual state-
ments would contain more contextual and sensory infor-
mation and show less allusion to cognitive processes and id-
iosyncratic information than fabricated statements. Many
who do research in this area have shown this to be an erro-
neous assumption, however, for these differences between
the two types of statements have not been consistently
found (Masip, Sporer, Garrido, & Herrero, 2005).
The theoretical framework for explaining how state-
ments of different origins may be distinguished is found in
the meta-cognitive reality monitoring processes defined by
Johnson (Johnson & Raye, 1981; Johnson et al., 1993).
Based on their proposals, numerous research studies have
been conducted to explore the characteristics that differenti-
ate statements of varying origin, such as memories of actual
events, imagination, dreams, fantasies, lies, or false memo-
ries derived from post-event information (Diges, 1995;
Henkel, Franklin, & Johnson, 2000; Johnson, 1988; Johnson,
Kahan, & Raye, 1984; Johnson, Foley, Suengas, & Raye,
1988; Lindsay & Johnson, 1989; Manzanero, 2006, 2009;
Manzanero & Diges, 1995; Manzanero, El-Astal, & Aróz-
tegui, 2009; Schooler, Gerhard, & Loftus, 1986; Suengas &
Johnson, 1988).
In a first approximation, Johnson and Raye (1981) pro-
posed that there are four types of essential attributes by
which we could differentiate between the two types of in-
formation stored in memory. Memories of perceptive origin
would have more contextual and sensory attributes and
more semantic details, while self-generated memories would
contain more information about cognitive operations. As
subsequent research was expanding the list of differentiating
attributes (see Table 1), the data was showing, simultaneous-
ly, that the presence of these distinctive features depends on
the influence of a host of factors.
Table 1. Dimensions of memory descriptions that could be important in
distinguishing their origin.
Sensory information
Details of the spatial and temporal context of the event (internal)
Details of the environmental context (external)
Allusions to cognitive processes
Hesitant expressions
Irrelevant or superfluous information
Explanations
Self-references
Exaggerations
Recall perspective
Personal opinions and comments
Fillers
Pauses
Spontaneous corrections
Changes of order
Length of the statement
Among other factors, the presence of characteristic fea-
tures in true statements, as opposed to statements arising
from imagined or suggested facts, would depend on the ac-
tivation (Diges, Rubio, & Rodríguez, 1992), previous
knowledge (Diges, 1995), the perceptive modality (Henkel et
al., 2000), the preparation (Manzanero & Diges, 1995), the
time delayed (Manzanero, 2006), the individual’s age (Com-
blain, D'Argembeau, & Van der Linden, 2005), the asking of
questions and multiple recall (Manzanero, 1994; Strömwall,
Bengtsson, Leander, & Granhag, 2004), and contextual fac-
tors (Campos & Alonso-Quecuty, 1998), as well as the type
of design used in the research conducted (Bensi, Gambetti,
Nori, & Giusberti, 2009).
On the other hand, the wide variability in memory origin
means that the characteristics differentiating fantasies, lies,
dreams, and post-event information are not the same. Even
for each modality, however, there are varying degrees of re-
move from the actual information. For example, changing a
small detail of an actual event—even a very important detail,
such as whether the role played in the event was witness or
protagonist—is not the same thing as fabricating the entire
event (Manzanero, 2009). In any case, false statements are
never entirely fabricated but originate, in part, from infor-
mation perceived from different sources that is re-elaborated
to create a new statement. Likewise, characteristics of the
statements could vary in relation to the participant’s ability
to generate a plausible statement.
Some previous studies have shown that criteria tradition-
ally used to distinguish actual victims from simulated vic-
tims, such as the emotions associated with their statements,
would not be useful with the ID population (Manzanero,
Recio, Alemany, & Pérez-Castro, 2013). We are not aware,
however, of any study on the characteristics that differenti-
ate true statements from false statements in this population.
This was the reason for conducting the following experi-
ment: to analyze the differences between statements given
by actual and simulated victims with ID, using the features
proposed under the framework of Reality Monitoring (RM)
processes—the ultimate purpose being to develop proce-
dures adapted for these victims.
Previous research studies (Manzanero, López, & Aróz-
tegui, submitted) using participants with no intellectual disa-
bility, who were asked to assume the perspective of either
false protagonist or actual bystander for an automobile acci-
dent, showed that the former were more heterogeneous,
phenomenologically, than the latter, although the two types
of statements differed on very few points (Figure 1). The
hope was that similar results would be obtained in this study.
Method
Participants
Twenty-nine persons with intellectual disability partici-
pated in the study. Thirteen of the participants were actual
victims, with a mean IQ of 60.72 (SD=9.67) and a mean
chronological age of 35.18 years (SD=7.16), and sixteen
were simulated victims, with a mean IQ of 59.30 (SD=9.44)
and a mean chronological age of 33.75 years (SD=6.78).

340 Antonio L. Manzanero et al.
anales de psicología, 2015, vol. 31, nº 1 (enero)
Figure 1. HDV graph of the content criteria for true statements (black dots)
and false statements (white dots), with all content criteria taken into account.
Correct classification = 94.3%. Sammon’s error = .034. (Manzanero et al.,
submitted)
Procedure
To conduct this research, a real event was chosen that
happened two years ago—a day trip taken by a group of per-
sons with ID from the Carmen Pardo-Valcarce Foundation,
during which the bus they were traveling in caught fire. A
researcher selected the participants, all of comparable IQ, on
the basis of criteria for the ―true‖ group—did go on the day
trip—and the ―false‖ group—did not go on the day trip but
knew about the event from references made to it. All per-
sons with ID who participated in the study (or their legal
guardians) signed a consent for voluntary participation. Each
of the persons with ID was given instructions and informed
of the purpose of the research. In addition, those partici-
pants who did not go on the day trip were given a summary
of the most important information about the trip, such as
the location, the trip’s primary complication, and how the
day went. We increased the ecological validity of our study
by encouraging all participants in the two groups to do their
best when giving their testimony. However, to avoid putting
them under too much pressure to make the interviewer be-
lieve their testimony, we chose an incentive that was not
stressful—they would be invited for a soda if they succeeded
in convincing the interviewer that they had, in fact, experi-
enced the event. In addition, the persons with ID who be-
longed to the false statement group were told explicitly that
they had the option to lie and were assured there would be
no negative consequences if they did so, thereby preventing
undue tension.
Two ―blind‖ researchers, experts at interviewing and tak-
ing testimony, interviewed each participant individually. An
audiovisual recording was made of all interviews. The same
instructions were given for all interviews conducted: ―We
want you to tell us what happened when you went on the
day trip and the bus caught fire… from beginning to end,
with as much detail as you can give. We want you to tell us
even things that you might think are not very important.‖
Once the free statement was obtained, all participants were
asked the same questions: Who were you with? Where was
it? Where were you going? What did you yourself do? and
What happened afterwards? The interviews were conducted
in random order.
The interview tapes were transcribed to facilitate analysis
of the phenomenological characteristics of the statements,
with any reference to the participant’s group eliminated.
Two trained evaluators assessed each statement individually
on each of the content criteria proposed in the RM proce-
dure (see Table 2), and then an interjudge agreement was
reached. The degree of agreement between encoders [AI =
agreements / (agreements + disagreements)] for all meas-
urements analyzed was greater than .80 (Tversky, 1977).
For correcting amount of detail, a chart was made of the
micropropositions, describing as objectively as possible what
happened in the actual event.
The remaining measurements are defined as follows:
- sensory information: information referring to sensory and ge-
ographical data that appeared in reality: colors, sizes, posi-
tions…
- contextual information: information referring to spatial and
temporal data about the area where the accident took place
- allusions to cognitive processes: information in which some cog-
nitive process is explicitly mentioned: I imagined, I saw, I
heard, I remember… my attention was focused on, some-
thing makes me think…
- hesitant expressions: implies doubt about what is being de-
scribed (it could be, it seems that, I think that, it’s likely...)
- irrelevant information: information that is correct but is not a
central part of the event
- explanations: information that expands upon the description
of the facts by providing a functional reference
- self-references: references the participant makes to himself
when describing the event
- exaggerations: descriptions that, by being excessive or lack-
ing, distort the facts
- personal opinions and comments: assessments of aspects of the
event and the participant’s personal additions
- Fillers: pet words or phrases that are repeated out of habit
throughout the statement
- pauses: silences during the participant’s narration of the
facts
- spontaneous corrections: corrections occurring in the descrip-
tion of the facts
- changes of order: alteration of the event’s natural order of oc-
currence: introduction, development, and conclusion
- length: number of words in the statement
All measurements, with the exception of length, were
measured by counting the number of times each one oc-
curred in the statements.

Evaluating the Credibility of Statements Given by Persons with Intellectual Disability 341
anales de psicología, 2015, vol. 31, nº 1 (enero)
Results
Factorial analysis (ANOVA) of the content criteria proposed
in RM showed that only amount of detail [F(1.31)=19.800, p
<.01, η2=.398, 1-β=.990] and length of statement
[F(1.31)=5.526, p <.05, η2 =.156, 1-β =.624] were significant.
There were no significant effects on the rest of the criteria.
Table 2 shows the mean scores and standard deviations for
false statements and true statements and the totals for each
criterion.
Table 2. Mean and standard deviation for content criteria and effect size
(R2), in relation to statement origin.
False
Statement
True
Statement
Total
M
SD
M
SD
M
SD
R2
Amount of
detail **
7.35
3.60
13.93
4.74
10.43
5.29
.398
Sensory in-
formation
1.11
1.72
1.53
1.64
1.31
1.67
.016
Contextual
information
3.70
1.49
4.80
1.89
4.21
1.75
.100
Cognitive
processes
0.47
1.00
0.66
1.04
0.56
1.01
.010
Hesitant ex-
pressions
1.35
1.27
2.03
1.75
1.67
1.53
.051
Irrelevant in-
formation
0.17
0.52
0.40
0.82
0.28
0.68
.028
Explanations
0.52
0.51
0.93
1.33
0.71
0.99
.043
Self-
references
5.17
4.55
7.60
8.02
6.31
6.42
.037
Exaggerations
0.05
0.24
0.20
0.56
0.12
0.42
.029
Opinions /
comments
0.94
1.02
1.40
1.24
1.15
1.14
.042
Fillers
7.29
6.44
6.46
7.42
6.90
6.82
.004
Pauses
9.76
7.22
20.26
21.92
14.68
16.50
.104
Corrections
0.17
0.39
0.13
0.35
0.15
0.36
.004
Changes of
order
0.76
0.90
1.26
1.27
1.00
1.10
.053
Length*
144.11
75.14
249.06
166.07
193.31
134.91
.156
** Significant effects p <.01; * significant effects p <.05.
As a way to appreciate the differences between the two
types of statements, with all the measurements analyzed tak-
en into consideration, the data was represented graphically
through a high-dimensional visualization (HDV) technique
used in other studies (Buja et al., 2008; Manzanero et al.,
2009; Steyvers, 2002), and a cluster analysis was performed
to classify participants into two groups.
As may be appreciated from the graph in Figure 2, one
possible explanation for the scant difference between the
two types of statements stems from intersubject variability,
which would indicate that this technique has low diagnostic
capability. If we tried to classify the two types of statements
based on all the phenomenological characteristics considered
in the RM technique, K-Means Cluster Analysis grouped 25
cases as false and 7 as true. When cluster A is considered
equal to simulation and B equal to actual, the false state-
ments were correctly classified in 16 cases (94.1% of total
false statements), while true statements were correctly classi-
fied in 6 cases (40% of total true statement). As may be ob-
served in HDV graph, the main reason is that the actual vic-
tims’ statements are more heterogeneous than the simulated
victims’ statements—for those of the former group are,
phenomenologically, more similar to those of the latter
group, in some cases.
Figure 2. HDV graph of the content criteria for true statements (white
dots) and false statements (black dots), with all content criteria taken into
account. Sammon’s error = .013.
When cluster groups are considered, factorial analysis
(ANOVA) of the content criteria proposed in RM showed
that amount of detail [F(1.31)=16.375, p <.01, η2=.353, 1-
β=.975], explanations [F(1.31)=5.218, p <.05, η2=.148, 1-
β=.599], self-references [F(1.31)=5.449, p <.05, η2=.154, 1-
β=.618], exaggerations [F(1.31)=5.300, p <.05, η2=.150, 1-
β=.606], pauses [F(1.31)=7.320, p <.05, η2=.196, 1-β=.745],
and length of statement [F(1.31)=64.663, p <.01, η2=.683, 1-
β=.1.000] were significant (see Table 3).
Table 3. Mean and standard deviation for content criteria and effect size
(R2), in relation to cluster groups
Cluster A
Cluster B
M
SD
M
SD
R2
Amount of detail **
8.80
4.36
16.28
4.15
.332
Sensory information
1.04
1.48
2.28
2.05
.068
Contextual information
3.96
1.81
5.14
1.21
.049
Cognitive processes
0.44
1.00
1.00
1.00
.022
Hesitant expressions
1.58
1.44
2.00
1.91
.020
Irrelevant information
0.20
0.50
0.57
1.13
.021
Explanations *
0.52
0.58
1.42
1.71
.120
Self-references *
5.00
4.18
11.00
10.51
.125
Exaggerations *
0.04
0.20
0.42
0.78
.122
Opinions / comments
1.04
1.13
1.57
1.13
.006
Fillers
6.20
6.42
9.42
8.10
.007
Pauses *
10.88
11.23
28.28
25.03
.169
Corrections
0.16
0.37
0.14
0.37
-.033
Changes of order *
0.76
0.83
1.85
1.57
.146
Length**
135.24
63.50
400.71
116.92
.673
** Significant effects p <.01; * significant effects p <.05.

342 Antonio L. Manzanero et al.
anales de psicología, 2015, vol. 31, nº 1 (enero)
Conclusions
As noted in the introduction, there is an abundance of litera-
ture that points out inconsistencies in the attributes differen-
tiating true statements from false statements, as well as the
irrelevance of RM procedure criteria, on the whole, for dis-
tinguishing between true and false statements. Likewise,
from the results obtained in this study, we can conclude that
the above-mentioned technique is also not valid for distin-
guishing between statements given by actual and simulated
victims with ID. The lack of effect on most of the criteria
would be due to an enormous variability and, in some cases,
to the floor effect for, generally speaking, the statements
were not very rich, phenomenologically.
Of the 15 criteria analyzed, however, there were two
(amount of detail and length) that were significant for dis-
criminating between the two types of statements and, there-
fore, could be of some help in distinguishing the origin of
the statements. Thus, the temptation would be to use only
these two criteria for an objective analysis of credibility and
to discard the remaining criteria.
This approach, which would mean fewer criteria, should
be discarded, however, because whether these two criteria
are present most likely depends on a great variety of factors,
such as the type of event described, the time elapsed, and
the witness’s abilities, for example. If the criteria that enable
us to distinguish between true and false statements are the
amount of detail and the length of the statement—the first
also being especially important in evaluating a testimony as
―true‖—what happens with all those individuals who have
limited vocabulary, semantic and autobiographical memory
deficits (without which they cannot satisfactorily reproduce
conversations), or difficulty situating events in a given con-
text? The majority of persons with ID have trouble relating a
vivid event in rich detail; they tend to be even less likely than
the population without ID to include important details of
the event (Dent, 1986; Kebbell & Wagstaff, 1997; Perlman,
Ericson, Esses, & Isaacs, 1994).
By the same token, many persons with ID also have
great difficulty situating events in time and space (Bailey et
al., 2004; Landau & Zukowsky, 2003). Therefore, using only
the two criteria shown to be significant in the study, one
runs the risk of issuing an erroneous assessment of credibil-
ity—and the revictimization that would result.
Discarding the 13 non-significant criteria does not seem
appropriate either, however, for as the cluster analysis of all
criteria shows, we would still be able to distinguish 68.75%
of the statements correctly, even though they vary widely.
The problem is that, even with sound decision-making abil-
ity, it is difficult to take 15 criteria into consideration simul-
taneously—and, in any case, there is an 60% chance of a
false positive. Let us remember that, in forensic psychology,
the proposed maximum rate of error for a technique to be
accepted as valid is 0.4% (Manzanero & Muñoz, 2011;
Rassin, 1999; Wagenaar, Van Koppen, & Crombag, 1993).
Further research with these criteria, along with a system
of analysis that would enable all indicators to be taken into
account in making a decision, might shed more light on con-
tent-based lie detection procedures.
These results, however, are contrary to those found in
the previous research mentioned in the introduction, which
was conducted with developmentally normal persons (Man-
zanero, et al., submitted), where the dispersion of points on
the graph was observed to be greater for statements given by
participants assuming the perspective of false protagonist
than for those assuming the actual perspective (see Figure
1). In that study, in contrast to this one, the two types of
statements could be distinguished with a 94.3% chance of
accuracy. At any rate, this difference in the results could be
accounted for by differences between the two studies in
terms of not only the participants but also the events—for
an actual event was used for the present study, but a filmed
event and a different type of fabrication was used for the
study with participants who did not have ID. It would be
advisable to conduct further research with different events
and different types of fabrication so that the results could be
generalized.
Limitations of the Study
Although the individuals available to us for the sample
were persons with mild and moderate ID—the deficit seen
in 80% and 10%, respectively, of persons with ID (Fletcher,
Loschen, Stavrakaki, & First, 2007)—we are adamant that
there is a need for research in this field with the group of
persons who have greater difficulty giving their testimony.
In future research studies, testimonies given by persons with
more severe ID should be analyzed on the basis of these cri-
teria because we understand that, the more severe the disa-
bility, the more difficult it is for the individual to narrate
with sufficient detail, to situate an event in a context, and to
reproduce conversations. Thus, in a population of persons
with severe ID or with a specific syndrome involving lan-
guage disorders, perhaps the credibility criteria that prove to
be significant for distinguishing between true and false
statements would be different.
Then again, the results obtained would be applicable on-
ly to those statements originating from an actual memory
and to false statements generated from information about an
event presented schematically. Research on persons with ID
would have to be expanded to include other types of state-
ments, such as those arising from false memories or those
originating in the imagination. In any case, false statements,
regardless of their origin, are never entirely fabricated but
originate, in part, from various sources of information and
are developed to create something new.
In conclusion, in light of our results, we may affirm that
there are complexities involved in analyzing the credibility of
testimony given by an adult person with ID and, even be-
yond that, in designing the supportive procedures required
to obtain a valid testimony. Given the bias that may condi-

Evaluating the Credibility of Statements Given by Persons with Intellectual Disability 343
anales de psicología, 2015, vol. 31, nº 1 (enero)
tion our intuitive credibility evaluation in persons with ID,
and because such an evaluation carries a significant margin
of error, it is absolutely essential that, in a law enforcement
or legal setting, individuals who specialize in ID would be on
hand when the testimony of a person with ID is to be evalu-
ated. By the same token, prior to evaluating the testimony,
the individual must be evaluated with regard to those abili-
ties that could impact each of the credibility criteria used to
distinguish between true and fabricated statements in this
population.
Acknowledgements.- This study is part of the research projects
entitled ―Entrevista, intervención y criterios de credibilidad en abu-
sos de carácter sexual en personas con discapacidad intelectual‖
[Interview, Intervention, and Credibility Criteria in Abuse of a Sex-
ual Nature in Persons With Intellectual Disability], financed by the
Fundación MAPFRE, and part of the project entitled ―Eliminating
Barriers Faced by Victims With Intellectual Disabilities: Police and
Judicial Proceedings With Victims of Abuse With Intellectual Disa-
bilities,‖ financed by the International Foundation of Applied Disability
Research (FIRAH). We wish to thank the persons with intellectual
disability from Sheltered Employment and the Sheltered Work-
shops at Fundación Carmen Pardo-Valcarce who collaborated on this
study as actual and simulated victims.
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(Article received: 21-1-2013; revision received: 16-4-2013; accepted: 25-7-2013)