Psychometric properties of the Social Interaction Anxiety Scale and separation criterion between...

Psychometric properties of the Social Interaction

Anxiety Scale and separation criterion between

Spanish youths with and without subtypes

of social anxiety

Ihab Zubeidat a, Jose Marıa Salinas b,*, Juan Carlos Sierra a,Antonio Fernandez-Parra a

a Department of Personality, Assessment and Psychological Treatment,

University of Granada, Spainb Department of Social Psychology and Methodology of Behavioral Sciences,

University of Granada, Spain

Received 22 June 2006; received in revised form 11 July 2006; accepted 22 September 2006

Abstract

In this study, we analyzed the reliability and validity of the Social Interaction Anxiety Scale (SIAS) and

propose a separation criterion between youths with specific and generalized social anxiety and youths

without social anxiety. A sample of 1012 Spanish youths attending school completed the SIAS, the

Liebowitz Social Anxiety Scale, the Social Avoidance and Distress Scale, the Fear of Negative Evaluation

Scale, the Youth Self-Report for Ages 11–18 and the Minnesota Multiphasic Personality Inventory-

Adolescent. The factor analysis suggests the existence of three factors in the SIAS, the first two of which

explain most of the variance of the construct assessed. Internal consistency is adequate in the first two

factors. The SIAS features an adequate theoretical validity with the scores of different variables related to

social interaction. Analysis of the criterion scores yields three groups pertaining to three clearly differ-

entiated clusters. In the third cluster, two of social anxiety groups – specific and generalized – have been

identified by means of a quantitative separation criterion.

# 2006 Elsevier Ltd. All rights reserved.

Keywords: Social anxiety; Social Interaction Anxiety Scale; Spanish youths; Psychometric properties

Journal of Anxiety Disorders 21 (2007) 603–624

* Corresponding author. Departamento de Psicologıa Social y Metodologıa, Facultad de Psicologıa, Universidad de

Granada, 18071 Granada, Spain.

E-mail address: [email protected] (J.M. Salinas).

0887-6185/$ – see front matter # 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.janxdis.2006.09.010

mailto:[email protected]

http://dx.doi.org/10.1016/j.janxdis.2006.09.010

1. Introduction

Social anxiety is a complex disorder that includes different components and dimensions to

consider in its assessment. Social anxiety has been defined as an experience of stress, discomfort

and fear related to social situations, which leads to a deliberate avoidance of such situations and

to the fear of receiving negative evaluations from others (Watson & Friend, 1969). People with

social anxiety have negative thoughts in interpersonal situations and blame themselves rather

than the situation for the deficiencies, which increases their heart rate and blood pressure (Beidel,

Turner, & Dancu, 1985). Comorbidity with other disorders worsens the symptoms and leads to a

high suicide rate (Davidson, Hughes, George, & Blazer, 1993; Lepine & Lellouch, 1995).

Epidemiological studies (Magee, Eaton, Wittchen, McGonagle, & Kessler, 1996; Schneier,

Johnson, Hornig, Liebowitz, & Weissman, 1992) reported that in 19–29% of cases social phobia

is present in an isolated way, which suggests that 70–80% of patients have at least another

diagnosed psychopathological disorder besides social anxiety (Lecrubier, 1998). Although all

phobic and anxiety disorders affect women in higher percentages than men, this difference is not

very clear in social phobia, since some studies have only found a slight female predominance

(Myers, Weissman, & Tischler, 1984) and others have reported an equal distribution between

both sexes (Amies, Gelder, & Shaw, 1983). Turk et al. (1998) argued that, although most

epidemiological studies have obtained a higher prevalence rate for social anxiety disorder in

women, the difference between both sexes disappears when clinical studies are considered.

Kessler, Stein, and Berglund (1998) and Magee et al. (1996) reported a prevalence of 15.5% in

women compared to 11.1% in men. Similarly, the transcultural research of Weissman et al.

(1996) showed higher prevalence rates of social anxiety in women than men in the United States,

Canada and Puerto Rico. However, differences shown in the study carried out by Weiller,

Bisserbe, Boyer, Lepine, and Lecrubier (1996) between women from a sample of patients with

social anxiety (53.5%) and those from a sample from the general population (43.1%) are not

significant. Besides, when social phobia is coupled with avoidant personality disorder, more

cases of men than women are reported (Echeburua, 1993).

In the adolescent population, a number of studies (Beidel & Turner, 1988; Essau, Conradt, &

Petermann, 1999; Hayward, Killen, Kraemer, & Taylor, 1998; Wittchen, Stein, & Kessler, 1999)

reported a prevalence ranging between 1.6% and 10%. Anderson, Williams, McGee, and Silva

(1987) and Lapouse and Monk (1959) revealed that adolescent girls show more social fears and

worries than boys. Yet, the only study based on the DSM-III criteria was that of Anderson et al.

(1987), who reported a .2% percentage of social phobia in adolescent girls compared to 1.0% in

boys. Moreover, Strauss and Francis (1989) argue that girls tend to be given the diagnosis of

social phobia more commonly than boys on the basis of the DSM-III criteria in clinical samples

of anxiety disorders. Adolescent females have been shown to be more concerned than males

about the judgment of others on their appearance and behavior (Nolsen-Hoeksema & Larson,

1992; Rosen & Aneshensel, 1976). In fact, the percentages of interiorization problems are higher

in the former than in the latter (Bernstein, Garfinkel, & Hoberman, 1989; Kashani, Orvaschel,

Rosenberg, & Reid, 1989; Quay & La Greca, 1986). This highlights the greater vulnerability of

adolescent girls to experiencing feelings of social anxiety compared to boys, which has

implications for their social functioning. These data show the need for preventive programs for

this disorder during childhood and adolescence (Tortella-Feliu, Servera, Balle, & Fullana, 2004).

Assessment of social anxiety and phobia must provide information about how to differentiate

between the specific and generalized subtypes. In its third revised edition (DSM-III-R) and fourth

edition (DSM-IV), the Diagnostic and Statistical Manual of Mental Disorders (American

I. Zubeidat et al. / Journal of Anxiety Disorders 21 (2007) 603–624604

Psychiatric Association, 1987, 1994) specifies the number of situations that generate fear in

subjects with social phobia, which has led to the designation of a specific subtype of social phobia

as opposed to a generalized type. Consequently, there have been several attempts to differentiate

between both forms of social anxiety. Heimberg, Hope, Dodge, and Becker (1990) and Turner,

Beidel, and Townsley (1992) consider that people who are most affected by situations related to

personal performance may be more likely to complain of a more limited number of so-called non-

generalized fears. There are other proposals to classify social anxiety subtypes (Heimberg, Holt,

Schneier, Spitzer, & Liebowitz, 1993; Olivares, Rosa, & Garcıa-Lopez, 2004; Stein, 1997).

However, the problem posed by this division is the lack of an exact quantification of the

expression ‘‘most situations’’ used in the DSM-IV (Holt, Heimberg, & Hope, 1992; Schneier,

Spitzer, Gibbon, Fyer, & Liebowitz, 1991). Such confusion affects not only the adult population

but also the adolescent one, for which there is little data available. According to Hofmann et al.

(1999), each researcher applies the expression ‘‘most situations’’ based on the estimation he or

she considers to be most appropriate. The distinction between the generalized form of social

anxiety and other forms specifically mentioned in the DSM-III-R and DSM-IV seems to be a

matter of degrees, i.e. the differences are quantitative. Heimberg, Liebowitz, Hope, and Schneier

(1995), Hofmann (2000) and McNeil (2001) argue that the difference between both subtypes of

social anxiety is quantitative and that instead of being differentiated by categories, there is a

continuum of severity. However, Hooke and Valentiner (2002) state that the separation between

generalized and specific social anxiety is qualitative; according to them, generalized social

phobia is understood as the fear of situations that involve interaction with others, whereas specific

social phobia is understood as the fear of a specific performance situation. This approach matches

that of Stemberger, Turner, Beidel, and Calhoun (1995). In turn, a distinction is made between

fears related to interaction and performance (Mattick & Clarke, 1998), which consistently

correlate with those related to generalized and specific social anxiety, respectively (Hooke,

Valentiner, & Kim, 2000). Moreover, people with generalized social anxiety have been shown to

report more social avoidance (Herbert, Hope, & Bellack, 1992; Holt et al., 1992), exaggerated

fears concerning negative evaluation (Holt et al., 1992), major social skills deficits (Tran &

Chambless, 1995) and more overall social anxiety (Turner, Beidel, Cooley, Woody, & Messer,

1994) than subjects with specific social anxiety.

There are currently few studies available on the distinction between generalized and specific

social anxiety in the adult population, and even fewer in the adolescent population. Therefore, there

is a need to carry out epidemiological studies on social anxiety to increase our knowledge about the

distinction between its two subtypes. Moreover, the few studies available are based on a strictly

quantitative separation criterion between both forms of social anxiety and the use of non-clinical

samples. In the adolescent population, most studies have involved English-speaking samples,

except for some carried out in Spanish-speaking populations, as is the case of Garcıa-Lopez (2000),

Olivares (2004), Ramos (2004) and Ruiz (2003). For this reason, research is needed to answer the

questions raised about the differences and similarities between the proposed subtypes of social

anxiety – the specific and the generalized subtypes, in particular – in this population. The scarcity of

studies carried out on this issue is due to several reasons. One of them is the fact that there are few

specific assessment instruments capable of distinguishing between specific and generalized social

anxiety in both the adult and the adolescent population. Yet, there are many social anxiety self-

report assessment tools available for these two populations in scientific literature, such as the Fear of

Negative Evaluation Scale (FNE) and the Social Avoidance and Distress Scale (SAD) (Watson &

Friend, 1969), the Social Phobia Anxiety Inventory (SPAI) (Turner, Beidel, Dancu, & Stanley,

1989), the Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale (SIAS) (Mattick &

I. Zubeidat et al. / Journal of Anxiety Disorders 21 (2007) 603–624 605

Clarke, 1998), the Liebowitz Social Anxiety Scale (LSAS) (Liebowitz, 1987), the Social Anxiety

Scale for Adolescents (SAS-A) (La Greca & Lopez, 1998), the Social Interaction Self-Statement

Test (SISST) (Glass, Merluzzi, Biever, & Larsen, 1982), the Davidson Brief Social Phobia Scale

(BSPS) (Davidson et al., 1991), the Interaction Anxiousness Scale (IAS) and the Audience

Anxiousness Scale (AAS) (Leary, 1983) and the Personal Report of Confidence as a Speaker

(PRCS) (Gilkinson, 1942; Paul, 1966). Although all these tests have adequate psychometric

properties, most of them have been unable to distinguish between the specific and generalized

forms of social anxiety because they lack separation criteria.

The Social Interaction Anxiety Scale (SIAS) (Mattick & Clarke, 1998) is an easy and quick

instrument to use and includes 20 items that measure anxiety experienced by people in social

interaction situations. It must be clarified that the SIAS and the SPS are used simultaneously to

measure complementary aspects of the concept of social anxiety. Although, it has been stated that

the former distinguishes best between the specific and generalized forms of social anxiety

(Heimberg, Mueller, Holt, Hope, & Liebowitz, 1992), the separation criterion between people with

specific and generalized social anxiety proposed by these authors is not fully clear. Some studies

(e.g., Habke, Hewitt, Norton, & Asmundson, 1997; Olivares, Garcıa-Lopez, & Hidalgo 2001;

Safren, Turk & Heimberg, 1998) have explored the factor structure of the SIAS and the SPS jointly,

with the purpose of verifying the two-factor model proposed by the original authors of such scales

(Mattick & Clarke, 1998), conferring a unidimensional character to each of them. Yet, the

psychometric properties of the SIAS have never been studied separately, since the studies

mentioned above analyzed a total of 40 items from both scales (SIAS and SPS). Besides, all these

studies were carried out with samples of the adult population, for which no separation criterion has

been presented that clearly distinguishes between different forms of social anxiety, and there is no

information available on this issue in adolescents. This, along with the need of instruments with

adequate psychometric characteristics to assess social anxiety in the Spanish population (Garcıa-

Lopez, Olivares, & Hidalgo, 2005), justifies our need to carry out a study on the psychometric

properties of the SIAS and propose a separation criterion based on the high scores obtained by

youths in this scale. Such criterion should allow us to detect different subtypes of social anxiety, and

will facilitate the study of the features of each of the mentioned groups separately.

In this instrumental study (Carretero-Dios & Perez, 2005; Montero & Leon, 2005), we

explored the psychometric properties of the 20 items of the SIAS in a sample of young Spanish

students. First of all, we examined the factor structure, reliability and construct and discriminant

validity; second, we aimed to establish a separation criterion capable of distinguishing between

youths with specific and generalized social anxiety and youths without social anxiety.

2. Method

2.1. Participants

The sample was selected by incidental sampling and included 1012 young secondary

education students from Granada (Spain); there were 430 males and 582 females, with an age

range between 13 and 19 (M = 15.80, S.D. = 1.48). Almost two thirds of the youths (n = 654)

were in second, third and fourth year of compulsory secondary education (Educacion Secundaria

Obligatoria); the rest were distributed similarly between students in first and second year of non-

compulsory secondary education (Bachillerato) (n = 187) and others that followed different

vocational training courses (Ciclos Formativos) (n = 171), such as cookery, hairdressing, etc.

Although most of the youths were only students, very few of them had a job as well. Almost one


third of the participants in the study had a boyfriend/girlfriend, although due to the age of the

subjects they were not legally recognized stable relationships.

2.2. Measures

2.2.1. Social Interaction Anxiety Scale (SIAS)

The SIAS (Mattick & Clarke, 1998) includes 20 items that are meant to be answered following a

5-point Likert scale. It has a high internal consistency (alpha = .93) and a 1-month test–retest

correlation coefficient above .90. Ries et al. (1998) revealed that the SIAS discriminates between

the generalized and specific subtypes of social phobia. Habke et al. (1997) reported three factors. In

Spain, Olivares et al. (2001) reported an internal consistency of .89 and obtained two factors that

explain 40.11% of thevariance. Nevertheless, the confirmatory factor analysis supported the single-

factor model and saturated all the items into a single one called ‘‘interaction social anxiety’’.

2.2.2. Liebowitz Social Anxiety Scale (LSAS)

The LSAS (Liebowitz, 1987) consists of 24 items that assess social or performance situations

by evaluating two components: the degree of fear or anxiety experienced and the degree of

avoidance reported by the subjects. Cox, Ross, Swinson, and Direnfeld (1998) reported high

internal consistency coefficients for the subscales social fear and social avoidance (alpha = .90);

similar data were reported by Heimberg et al. (1999). In Spain, Bobes et al. (1999) found internal

consistency coefficient values above .73 for all the LSAS scales; the intraclass correlation

coefficients found in the 2 weeks test–retest studies reported values above .82 for all subscales.

2.2.3. Social Avoidance and Distress Scale (SAD)

TheSAD (Watson & Friend, 1969) contains 28 items, half of which refer to subjective discomfort

in social situations and the other half of which refer to the active avoidance of such situations. This

scale has shown an internal consistency of .94 and a 1-month test–retest reliability of .68 (Watson &

Friend, 1969). Hofmann, DiBartolo, Holaway, and Heimberg (2004) reported a Cronbach’s alpha of

.93. In Spain, the reliability of the avoidance subscalewas .87, whereas that of social anxiety was .85

(Comeche, Dıaz, & Vallejo, 1995). In the study carried out by Garcıa-Lopez et al. (2001) on an

adolescent sample, a 10 days test–retest reliability of .85 was reported for the SAD.

2.2.4. Fear of Negative Evaluation Scale (FNE)

The FNE (Watson & Friend, 1969) assesses the degree of intensity with which individuals

experience fear of being negatively evaluated by others. Watson and Friend (1969) reported an

internal consistency coefficient of .94 and a 1-month test–retest reliability of .78. In Spain, an

internal consistency of .94 and .90 was obtained in the original version and the short version of the

scale, respectively. Garcıa-Lopez et al. (2001) reported a 10-day test–retest reliability equal to .84.

2.2.5. Youth Self-Report for Ages 11–18 (YSR)

The YSR (Achenbach, 1991; Achenbach & Edelbrock, 1978) consists of two parts; the first

one includes 17 items that assess the psycosocial skills of youths and the second one contains 112

items. Out of these items, 96 evaluate a number of problematic behaviors and the rest focuses on

prosocial behaviors. The study carried out by Verhulst, van der Ende, and Koot (1997) features

sound reliability and validity data. In the Spanish validation made by Lemos, Fidalgo, Calvo, and

Menendez (1992a, 1992b, 1992c) girls scored higher in internalized behaviors, whereas boys

scored higher in externalized ones (Lemos et al., 1992a). Abad, Forns, Amador, and Martorell


(2000) showed that internal consistency is more homogeneous and higher in internalized and

externalized syndromes than in narrowband ones. In the present study, we considered the

variables anxiety problems, anxiety/depression, withdrawal/depression, social problems,

internalizing syndromes and externalizing syndromes because they relate to social relations

of youths and because of their possible relation with social anxiety.

2.2.6. Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A)

The MMPI-A (Butcher et al., 1992) was adapted to the Spanish context by Jimenez-Gomez &

Avila-Espada. Butcher, Dahlstrom, Graham, Tellegen, and Kaemmer (1989) reported good

internal consistency values in the different scales. The scales depression (D), social introversion

(Si), anxiety (ANX), depression (DEP), alienation (ALN), low self-esteem (LSE) and social

discomfort (SOD) were used in this study because of their possible relation with interpersonal

relations and social anxiety in youths.

2.3. Procedure

The incidental sample of adolescents came from 13 secondary education schools of the

province of Granada (Spain). After obtaining consent from the teachers and the parents of the

youths, the students were assessed during a 4-month period. The self-reports were completed

collectively in the classroom in two 75-min sessions led by a single examiner. All the participants

were given the same instructions to answer, and participation was totally voluntary. In fact, 15

subjects refused to answer the self-reports and 9 dropped out after the sessions had started. The

subjects were never paid for participating.

3. Results

3.1. Descriptive statistics

In the SIAS, the mean of the youths of the total sample was 22.72 and the standard deviation

was 11.75. Table 1 summarizes the differences in the distribution of scores in the SIAS based on

sex, age, school year, romantic relationship and employment of the 1012 youths that participated

in the study.

In the SIAS scores, the difference between the means was only found to be significant in two

variables: sex (t = �3.07; p < .001) and school year (t = �2.14; p < .05). The mean of females’

scores in the SIAS was slightly higher than that of males. Similarly, the youths following

vocational training courses obtained mean SIAS scores that were slightly higher than those of the

group formed by adolescents in academic compulsory and non-compulsory education.

3.2. SIAS item characteristics

Table 2 shows data from the item analysis carried out for the SIAS, under the assumption of the

unidimensionality of the scale. It includes the mean, standard deviation, corrected item total

correlation and Cronbach’s alpha, if the item was deleted. The scale has a Cronbach’s alpha of .85.

As can be seen, the mean of the answers to the items is around 1.13 and the mean dispersion of

the answers to the items is 1.14. In all cases, the response range was 0–4. There were no items for

which none of the response options was chosen. The corrected item total correlation data

highlights the low correlation of items 5, 9 and 11 compared to the remaining items.


3.3. Unidimensional model validity

We started by testing the hypothesis of the original authors on the unidimensionality of the

SIAS. To this end, we carried out a confirmatory factor analysis (CFA) in which all the items

would be saturated. Fig. 1 shows the saturation of the 20 items of the SIAS scale in the construct

we attempted to measure (named Ais) and the error variance in each of them.

As Fig. 1 shows, 17 of the SIAS items managed to saturate at a value above .40 in the construct

we wanted to measure (Ais); the errors resulting from these items are notable. The three

remaining items (5, 9 and 11) have low saturation values of .27, .13 and .09, respectively;

moreover, the error produced by these items is fairly high, .93, .98 and .99, respectively. Also, the

value of the Chi-square statistic is high (x2 = 1727.51; d.f. = 170; p = .00), which shows that our

data does not match this unidimensional model.

3.4. Factor analysis and internal consistency

After verifying the adequate sensitivity of the items, the factor structure of the SIAS was

analyzed. To this end, the common factors were extracted by principal components method and

Varimax rotation with Kaiser normalization was applied to the initial structure in order to

determine the factorial structure (see Table 3). To determine the number of factors, we considered

eigenvalues higher than 1. The factor solution reveals a main dimension that clusters 17 items and

explains 29.91% of the variance, with an eigenvalue of 5.98; along with this factor, two less

important ones appear. The F2 factor explains 8.49% of the variance with an eigenvalue of 1.70

and is formed by three items (5, 9 and 11). Finally, the F3 factor, with an eigenvalue of 1.10,

explains 5.52% of the variance by grouping two items (6 and 8).


Table 1

Sample distribution and mean differences in SIAS scores based on socio-demographic variables

n (%) M (S.D.) t

Sex

Male 430 (42.50%) 21.43 (10.70) �3.07**

Female 582 (57.50%) 23.70 (12.40)

Age

13–15 years 483 (47.72%) 23.00 (11.83) .69

16–19 years 529 (52.30%) 22.50 (11.70)

School year

Comp./NC 841 (83.10%) 22.34 (11.50) �2.14*

Vocational 171 (16.90%) 24.60 (12.80)

Romantic rel.

With 296 (29.25%) 21.69 (11.60) �1.81

Without 716 (70.80%) 23.14 (11.80)

Employment

With job 86 (8.50%) 22.70 (12,30) �.02

Without job 926 (91.50%) 22.72 (11.70)

Note: Comp., compulsory secondary education; NC, non-compulsive secondary education; vocational, vocational

training courses; romantic rel., romantic relationship.* p < .05.

** p < .01.


Table 2

Means, standard deviations, (r) corrected item total correlation and internal consistency (Cronbach’s a) if the item is

deleted from the SIAS

Item M S.D. Corrected

item total

correlation

Cronbach’s

alpha if item

is deleted

(1) I get nervous if I have to speak with someone in authority

(teacher, boss, etc.) (Me pongo nervioso si tengo que hablar

con una figura de autoridad ( profesor, jefe, etc.))

1.37 1.09 .48 .84

(2) I have difficulty making eye-contact with others

(Me cuesta trabajo mirar a los ojos a otras personas)

.88 1.15 .42 .84

(3) I become tense if I have to talk about myself or my feelings

(Me pongo tenso si tengo que hablar sobre mı o mis sentimientos)

1.57 1.39 .40 .85

(4) I find difficulty mixing comfortably with the people I work with

(Me cuesta trabajo relacionarme comodamente con la

gente que trabajo)

.56 .92 .52 .84

(5) I find it easy to make friends my own age

(Encuentro facil hacer amigos de mi edad)

1.64 1.39 .25 .85

(6) I tense-up if I meet an acquaintance in the street

(Me pongo tenso si me encuentro a alguien conocido en la calle)

.57 .93 .40 .84

(7) I tense-up if I meet an acquaintance in the street

(Cuando me relaciono socialmente, me encuentro incomodo)

.50 .82 .53 .84

(8) I feel tense if I am alone with just one other person

(Me siento tenso si estoy con una sola persona)

.57 .89 .48 .84

(9) I am at ease meeting people at parties, etc. (Me encuentro

relajado cuando encuentro a gente en las fiestas, etc.)

1.47 1.38 .11 .86

(10) I have difficulty talking with other people

(Me cuesta trabajo hablar con otras personas)

.68 .97 .56 .84

(11) I find it easy to think of things to talk about

(Me es facil pensar en cosas de las que hablar)

2.15 1.30 .12 .86

(12) I worry about expressing myself in case I appear awkward

(Me preocupa decir lo que pienso por si parezco torpe)

1.15 1.21 .56 .84

(13) I find it difficult to disagree with another’s point of view

(Me cuesta trabajo expresar que discrepo del punto

de vista de otras personas)

.91 1.06 .47 .84

(14) I have difficulty talking to attractive persons of the

opposite sex (Me cuesta trabajo hablar con una persona

atractiva del sexo opuesto)

1.20 1.30 .51 .84

(15) I find myself worrying that I would not know what to

say in social situations (Me preocupa no saber que decir en

las situaciones sociales)

1.45 1.18 .56 .84

(16) I am nervous mixing with people I do not know well

(Me pongo nervioso cuando tengo que relacionarme con

personas que no conozco bien)

1.46 1.18 .57 .84

(17) I feel I will say something embarrassing when talking

(Presiento que voy a meter la pata cuando estoy hablando)

1.01 1.09 .65 .83

(18) When mixing in a group I find myself worrying I will be

ignored (Me preocupa que me ignoren cuando

estoy en un grupo)

1.79 1.36 .42 .84

(19) I am tense mixing in a group (Estoy tenso cuando

estoy en grupo)

.50 .87 .55 .84

(20) I am unsure whether to greet someone I know only

slightly (Cuando me encuentro con alguien que solo

conozco ligeramente no estoy seguro de si debo saludarlo)

1.29 1.32 .45 .84


Fig. 1. Saturation and error variance of the SIAS elements.

The internal consistency coefficients obtained with Cronbach’s alpha calculation that resulted

from the common factors reached values of .88 and .52 for the first and the second one,

respectively. Thus, we might expect that a rotation of the factors would group them in a more

homogeneous basic covariation pattern. Table 4 shows the data on the Varimax rotation with

Kaiser normalization that was carried out. Three clear factors appear: the first one includes eight

items and has a sum of squares with a saturation of 3.89; the second one is also formed by eight

items and has a sum of squares with a saturation of 300; the third one includes four items and has

a sum of squares with a saturation of 1.89.

In order to support the resulting factor solution, it is vital to analyze the homogeneity of the

answers for the isolated factors pointed out as relevant. To this end, internal consistency analysis

(Cronbach’s alpha) were carried out for the isolated rotated factors (see Table 4). The F1, F2 and

F3 factors had alpha values of .82, .74 and .54, respectively. As expected after the resulting factor

analysis, the first two isolated factors show high rates of internal consistency, which makes them

adequate for what is traditionally recommended as minimum necessary values (.70) (Anastasi,

1988; Muniz, 1998). The internal consistency of factor F3, which groups the lowest number of

items (4, 5, 11 and 12), three of which (5, 11 and 12) show a deficient corrected item total

correlation, obtained a low value (.54) as expected. This reinforces the consideration of F1 and

F2 as a relevant factor structure in the SIAS. We have called these three factors: ‘‘Anxiety

regarding social skills deficits,’’ ‘‘Anxiety regarding difficulty keeping an appropriate emotional

distance from others’’ and ‘‘Anxiety regarding discomfort caused when interacting with

people.’’


Table 3

Common factors analysis of the SIAS

Itema F1 F2 F3

17 .73 �.04 �.24

16 .66 �.07 �.19

12 .66 �.16 �.17

15 .65 �.20 �.36

10 .64 .23 �.12

19 .62 .16 .07

7 .61 .19 .28

14 .59 �.06 .13

4 .58 .33 �.01

13 .57 �.17 .00

1 .56 �.12 �.19

8 .56 .00 .4520 .54 �.16 .12

18 .52 �.32 �.26

2 .49 �.06 .29

3 .49 �.12 .16

6 .48 .03 .469 .10 .72 .03

5 .25 .62 �0.24

11 .10 .57 .15

Eigenvalue 5.98 1.70 1.10

Percentage of variance 29.91 8.49 5.52

Cronbach’s a .88 .52

a Items are listed in a decreasing order according to their saturation in the principal factor found.

3.5. Construct validity

The factor analysis discussed above is a procedure aimed at analyzing the entity of the

construct assessed; however, it is important to look to other sources of data that may help study

the quality of the SIAS. A great deal of research has focused on social anxiety, which allows for

the selection of variables whose relation to the variable measured by this instrument has been

verified. Table 5 shows the correlations established between the SIAS and other variables

assessed using the following anxiety and social phobia scales: LSAS, SAD and FNE. This table

also shows the correlations between the SIAS and some variables measured by the YSR and the

MMPI-A, which might be related to social anxiety in youths.

As shown in Table 5, all the correlations obtained were positive and significant. Overall, the

highest correlations were found between the SIAS and other variables measured by the specific

instruments (LSAS, SAD and FNE) that assess phobia and social anxiety. The variables assessed

by the YSR and the MMPI-A also had positive and significant correlations, although lower than

the ones just mentioned.

3.6. Criterion scores

The score histogram shown in Fig. 2, the result of the Kolmogorov–Smirnov normality test

(Z = 2.97; p < .001) and the asymmetry of data (asymmetry coefficient = .73) suggest there are

mixed populations in our data.


Table 4

Rotated factor solution using Varimax with Kaiser

Itema F1 F2 F3

15 .76 .12 .04

17 .70 .27 .18

18 .64 .11 �.12

12 .64 .27 .04

16 .63 .26 .12

1 .57 .20 .05

10 .48 .31 .39

13 .47 .36 �.03

8 .15 .70 .03

6 .08 .66 .04

7 .23 .60 .26

2 .22 .54 .00

14 .39 .46 .05

19 .37 .45 .28

20 .38 .43 �.06

3 .30 .43 �.03

9 �.17 .10 .705 .14 �.02 .7011 .00 �.04 .604 .34 .36 .45S.C. saturat. 3.89 3.00 1.89

Percent variance 19.44 15.01 9.47

Cronbach’s a .82 .74 .54

a Items are listed in a decreasing order according to their saturation in the principal factor found.

To separate such populations, we used the method of maximum likelihood and estimated the

parameters of a mixture of three normal distributions with Normix22 software (Wolfe, 1970).

Table 6 shows the estimates obtained for the three distributions.

Fig. 3 provides the graphic representation of the three distributions that led to the joint

distribution.

Table 7 shows the descriptive data of the three clusters we formed by assigning each individual to

the group he or she was most likely to belong to. We identified the groups that corresponded to the


Table 5

Pearson correlations between the SIAS scores and those of other variables

Variables Correlation with SIAS Confidence intervals

Anxiety of public performance .60 (.56–.64)

Avoidance of public situations .59 (.55–.63)

Anxiety in social interaction situations .47 (.42–.52)

Avoidance of social interaction situations .48 (.43–.53)

Total of social anxiety .62 (.58–.66)

Total of social avoidance .49 (.44–.54)

Total of social anxiety and avoidance .60 (.56–.64)

Social avoidance and distress .65 (.61–.68)

Fear of negative evaluation .48 (.43–.53)

Anxiety problems .40 (.35–.45)

Anxious/depressed .45 (.40–.50)

Withdrawn/depressed .44 (.39–.49)

Social problems .44 (.39–.49)

Internal syndromes .45 (.40–.50)

External syndromes .07 (.01–.13)

Depression (D) .22 (.16–.28)

Social introversion (Si) .39 (.34–.44)

Anxiety (ANX) .30 (.24–.36)

Depression (DEP) .32 (.26–.38)

Alienation (ALN) .31 (.25–.37)

Low self-esteem (LSE) .38 (.33–.43)

Social discomfort (SOD) .43 (.38–.48)

Negative treatment indicators (TRT) .31 (.25–.37)

Table 6

Parameters of the mixture of distributions

Distribution 1 Distribution 2 Distribution 3

Probability .50 .32 .18

Mean 14.75 27.14 36.70

Standard deviation 6.05 8.16 11.71

Table 7

Description of the clusters obtained

Cluster 1 Cluster 2 Cluster 3

No. of cases 568 340 104

Mean 14.33 29.52 46.27

Standard deviation 5.16 4.50 6.43

Value range 0–22 23–38 39–68

three clusters; the first group comprises the highest number of youths, without social anxiety, the

second one amounts to one third of the total sample and has very slight levels of social anxiety, so

that it is not diagnosed as such; finally, the third group includes about 10% of the total sample and is

diagnosed as having social anxiety. We called the first cluster ‘‘Youths without social anxiety,’’ the

second, ‘‘Youths with a mild social problem,’’ and the third, ‘‘Youths with social anxiety.’’

Within the third cluster, we determined two subtypes of social anxiety (specific and

generalized) using a separation criterion; that is to say, we applied a quantitative criterion to the

104 youths that scored above the cut point (40.34) established as equal to or greater than the sum

of the mean (22.72) plus one and a half times the standard deviation (17.62). The first group,

‘‘Specific social anxiety subtype’’ included the youths who obtained a cut point equal to or

greater than 40.34 and also answered ten or fewer social situations (SIAS items) showing high

anxiety levels (considered as 3 or 4). The second group, ‘‘Generalized social anxiety subtype’’

included the subjects who had a cut point equal to or greater than 40.34 and whose replies to

eleven or more social situations of the SIAS showed high anxiety levels. As a result, the

distribution of the 104 youths with social anxiety was the following: 66 belonged to the specific

social anxiety subtype and 38 belonged to the generalized subtype. The means of these two


Fig. 2. Histogram of the SIAS scores.

groups were 42.63 (S.D. = 2.50) and 52.60 (S.D. = 6.30) for the specific and generalized

subtypes, respectively; the difference between such means was significant (t = �9.30; p < .00).

4. Discussion

The aim of this study was to calculate the psychometric guarantees of the Social Interaction

Anxiety Scale (SIAS) (Mattick & Clarke, 1998). We wanted to propose a separation criterion to

distinguish between youths without social anxiety and youths with subtypes of social anxiety

(mainly the specific and generalized subtypes), given that there are no such criteria in scientific

literature. Two points are essential: first, the self-reports used in the assessment of social anxiety

and behavior must have adequate psychometric guarantees; second, in instruments specialized in

distinguishing social anxiety subtypes, such as the SIAS (Heimberg et al., 1992), there should be

a criterion that is able to detect groups of specific and generalized social anxiety.

The first result that should be pointed out concerns differences in social anxiety based on

certain socio-demographic variables. For example, young girls had a slightly higher mean than

boys in social anxiety, which was statistically significant. This matches the findings of Myers

et al. (1984), who found a slight predominance of social anxiety in females compared to males. In

the adolescent population, the only study based on the DSM-III criteria was that of Anderson

et al. (1987), who reported social anxiety percentages of .2% compared to 1.0% for girls and

boys, respectively. Along these lines, the studies carried out by Crick and Ladd (1993), La Greca

and Stone (1993) and Vernberg, Abwender, Ewell, and Beery (1992) reported that girls feature

higher levels of social anxiety than boys, especially regarding the issue of social evaluation.

Concerning school year, the mean of the youths following vocational training courses was

slightly higher than that of the group formed by adolescents in second, third and fourth year of

compulsory secondary education and first and second year of non-compulsory secondary

education. This result could be explained by the fact that students following vocational training

courses are required to learn a series of practical skills and implement them to have an adequate

social functioning; in many of these vocational training courses (hospitality, hairdressing, etc.)


Fig. 3. Components of the mixture of distributions.

the examinations of students involve a public display of such skills. Besides knowledge, it is

important to show certain interpersonal skills, which may lead these students to be seen as

sensitive to the evaluation when they answer the questionnaires. Magee et al. (1996) also found

differences in social anxiety based on education level.

The analysis carried out on the quality of the items raises certain doubts, since three items (5, 9

and 11) out of the 20 that form the SIAS showed a very low correlation with the rest of the items

of the scale. This matches the study of Olivares et al. (2001). Moreover, if items 9 or 11 were

eliminated, Cronbach’s alpha would increase to .86. In these last two items and the fifth one, data

are problematic and should be taken into account when interpreting the reliability of the scale and

the factor structure. Cronbach’s alpha is decreased by eliminating the remaining items, except in

the case of 5, when it stays the same. In fact, the low corrected item total correlation of these three

items can be interpreted in two ways. The first interpretation refers to the fact that such items are

worded differently than the rest. That is to say, items 5, 9 and 11 of the SIAS are positively

worded and have to be inverted for their score to be considered, whereas the remaining 17 items

are negatively worded. The second interpretation relates to the content of such items. The items

in question refer to discomfort in social interaction situations, whereas the remaining ones

measure anxiety experienced in such situations. It must be stated that no studies in scientific

literature have attempted to analyze the behavior of SIAS items separately. Instead, the different

studies carried out (Habke et al., 1997; Heimberg et al., 1992; Mattick & Clarke, 1998; Olivares

et al., 2001; Safren et al., 1998) have analyzed the 40 items of the SIAS and the SPS jointly. In any

case, future studies should include more items – at least three – with a positive format in order to

reach a balance between positive and negative items and reduce any possible biases.

If the SIAS is considered to be unidimensional, we found that the internal consistency

(Cronbach’s alpha) has a value of .85. This reliability index is adequate and close to the one (.86)

found by Heimberg et al. (1992). Moreover, these two values are close to the one (.93) found by

the authors of the SIAS scale (Mattick & Clarke, 1998). Nevertheless, the doubts mentioned

above concerning the quality of the items led us to carry out a confirmatory analysis of the

construct measured to test the unidimensionality of the SIAS argued by Mattick and Clarke

(1998). Again, we obtained evidence on the low saturation in the construct and the high degree of

error produced by items 5, 9 and 11. Apart from this, the value of the Chi-square statistic obtained

was high, highlighting the incongruence between our data and the unidimensional model

proposed by such authors. These first findings highlight the need to carry out an independent

factor analysis of the SIAS, without considering the SPS jointly. Results of the principal

unrotated factor analysis reveal the existence of two factors. The third factor will not be taken into

consideration because its eigenvalue is not significantly greater than one (1.03) and its items

reach a higher factor saturation in F1. This matches the confirmatory factor analysis, which

rejected the single-factor model. That is to say, we find a first dominant factor that groups 17 out

of the 20 items of the SIAS and a second one formed by the three positive items (5, 9 and 11).

These first data suggest that the SIAS assesses mainly, but not only, a dimension that refers to the

physiological anxiety experienced in social interaction situations that could be called ‘‘Anxiety

regarding social interaction.’’ However, there seems to be another less relevant dimension than

the first one that refers to the discomfort experienced by people in social situations, which could

be called ‘‘Discomfort regarding social interaction.’’ This result suggests that the factor structure

found for the SIAS does not reflect one single dimension as reported by Mattick and Clarke

(1998), and that the elements included in this scale must be carefully examined. Only the first

factor has a good internal consistency (an alpha value of .88). Moreover, all the items included in

the first factor feature a correlation with the rest that is equal to or higher than .40, which confers


an adequate consistency and quality to the items of this factor. As regards the second factor, apart

from having an inadequate internal consistency (.52), its items show a correlation with the rest of

items that is lower than .30. If other studies eventually confirm the existence of this second factor,

we believe the scale should be modified and include more items to assess this dimension with an

adequate reliability.

All this highlights the complexity of the construct we are evaluating and the need to carry out

an orthogonal rotation of these three factors found in order to be certain about the factor structure

of the SIAS. To this end, the Varimax rotation with Kaiser normalization procedure was carried

out to find possible covariations that may support the lack of unidimensionality of the SIAS.

Again, the results highlight the existence of more than one factor measured by this scale. This

time, three factors were identified which cluster 8, 8 and 4 items for factors F1, F2 and F3,

respectively. The saturation of these items in each factor was fairly high, and the internal

consistency coefficients (Cronbach’s alpha) had adequate values for the first two factors and

inadequate ones for the third one. Analyzing the items included in each of these three factors, it

can be seen that the first one contains elements that mainly refer to anxiety experienced in

interaction situations that involved implementing certain social skills, such as ‘‘I get nervous if I

have to speak with someone in authority (teacher, boss, etc.)’’ (item 1), ‘‘I worry about

expressing myself in case I appear awkward’’ (item 12), ‘‘I find it difficult to disagree with

another’s point of view’’ (item 13) or ‘‘I feel I’ll say something embarrassing when talking’’

(item 17). The second factor clusters items that refer to anxiety produced by interaction in social

situations that require reducing emotional distance or establishing ties of affection with others,

including items, such as ‘‘I become tense if I have to talk about myself or my feelings’’ (item 3),

‘‘I tense-up if I meet an acquaintance in the street’’ (item 6), ‘‘I feel tense if I am alone with just

one other person’’ (item 8) or ‘‘I have difficulty talking to attractive persons of the opposite sex’’

(item 14). Finally, the third factor groups items that refer to the discomfort felt in situations that

involve relating to people and includes the following items: ‘‘I find difficulty mixing

comfortably with the people I work with’’ (item 4), ‘‘I find it easy to make friends my own age’’

(item 5), ‘‘I am at easy meeting people at parties, etc.’’ (item 9), ‘‘I find it easy to think of things to

talk about’’ (item 11). Thus, we could call the first factor ‘‘Anxiety related to social skills

deficits,’’ the second one, ‘‘Anxiety regarding difficulty keeping an appropriate emotional

distance from others,’’ and the third one, ‘‘Anxiety regarding discomfort caused when

interacting with people.’’ In terms of the number of factors, this finding matches those of Habke

et al. (1997) and Safren et al. (1998), who also described three factors. However, their analysis

was based on the joint study of the 40 items of the SPS and SIAS scales. Thus, the three factors

we have found in our study are a relevant novelty regarding the review of the factor structure of

the SIAS. Other studies carried out on this issue (for example, Heimberg et al., 1992; Olivares

et al., 2001) did not provide data on the possible bidimensionality or tridimensionality of the

SIAS. Instead, their results responded to the unidimensionality proposed by the original authors

of the scale (Mattick & Clarke, 1998).

Apart from the factor analysis, there are other sources possible to study the quality of the

SIAS; one of them is to analyze its correlation with other variables. The results show that the

SIAS has significant correlations with the following variables assessed by specialized

instruments to measure social anxiety and phobia (LSAS, SAD and FNE): anxiety of public

performance, avoidance of public situations, anxiety in social interaction situations, avoidance of

social interaction situations, total of social anxiety, total of social avoidance, total of social

anxiety and avoidance, social avoidance and distress, fear of negative evaluation. Moreover,

significant correlations were shown, on one side, between the SIAS and some variables measured


by the YSR/11-18, such as anxiety problems, anxious/depressed, withdrawn/depressed, social

problems, internal syndromes and external syndromes; and, on the other side, between the SIAS

and others assessed by the MMPI-A, such as depression (D), social introversion (Si), anxiety

(ANX), depression (DEP), alienation (ALN), low self-esteem (LSE), social discomfort (SOD)

and negative treatment indicators (TRT). Furthermore, the highest correlations were found

precisely between the SIAS scores and social anxiety and avoidance. Similarly, it has been found

that individuals with generalized social anxiety report more social avoidance (Herbert et al.,

1992; Holt et al., 1992), an exaggerated fear of negative evaluation (Holt et al., 1992), major

social skills deficits (Tran & Chambless, 1995) and more overall social anxiety (Herbert et al.,

1992; Holt et al., 1992; Turner et al., 1994) than individuals with specific social anxiety, which

matches our findings. In the same way, Mennin, Heimberg, and Jack (2000) reported that patients

with generalized social anxiety obtain highly severe measures in social anxiety and avoidance,

general anxiety, cognitive symptoms of anxiety, and depressive mood. Finally, interaction

anxiety has been found to be associated with continuous indices of low self-esteem, trait anxiety

and shyness (Hooke et al., 2000).

Finally, we suggest that, as the histogram shows, the SIAS scores do not form one single

distribution. We believe that, instead, they reflect the mixed distributions that highlight the

existence of three groups of youths; the second of which has some kind of social problem but is

considered different from the third group called, ‘‘Youths with social anxiety.’’ This finding is

new compared to the ones currently seen in scientific literature, since most studies (Stein,

McQuaid, Laffaye, & McCahill, 1999; Stein, Walker, & Forde, 1996; Weiller et al., 1996;

Wittchen et al., 1999) do not mention this second group, although they identify a group with

social anxiety, whose percentage matches that of our third group (about 10%). These studies

show that social phobia has a prevalence ranging between 2% and 16%. Recently, a prevalence

rate of 8.2% has been found in a community sample of adolescents in the South-East of Spain

(Olivares, 2004). Understood in this way, subjects with social anxiety are not those with extreme

scores in a normal distribution. Instead, they make up a clearly differentiated population with its

own features, whose scores in the questionnaire partially overlap with those of the other groups.

Of all the different procedures we used to differentiate the mixed populations – K-means

cluster means, two-stage cluster, mixture of distributions that always suggested the existence of

three different groups of youths – we chose to present the results obtained in the mixture of

distributions estimation. We did so because the estimations obtained from the parameters will

allow other researchers to set the most adequate cut points on a case by case basis depending on

their interests and objectives. In our case, facing the lack of separation criteria to distinguish

between the two forms–specific and generalized – of social anxiety, we attempted to determine

social anxiety subtypes within the third established group of the 104 youths with social anxiety

that had obtained a mean in the SIAS above the cut point (38) found. To do so, we applied a

quantitative separation criterion to this third group. Thus, the youths that showed high anxiety

levels (3 or 4) in more than half (10) of the situations of the SIAS were assigned to the generalized

social anxiety subtype. The others – those whose answered showed a high level of anxiety in 10 or

fewer situations – were assigned to the specific social anxiety subtype. Both subtypes of youths

with specific and generalized social anxiety obtained by applying this separation criterion

included 66 and 38 subjects, respectively. About two thirds (63%) corresponded to the

generalized subtype and one third (37%) involved the specific subtype. Our separation criterion

between both forms of social anxiety may be just as valid as any other criterion used by different

studies (Furmark, Tillfors, Stattin, Ekselius, & Fredrikson, 2000; Heimberg & Holt, 1989;

Kessler et al., 1994; Mannuzza et al., 1995; Quero, Banos, Botella, & Gallardo, 2003; Stein,


Torgrud, & Walter, 2000). In these instances of research, as in our study, all the criteria used were

quantitative, although there were variations in the number of subtypes with social anxiety found

among the different studies. For example, the qualitative criterion used in the present study

partially matches the studies carried out by Quero et al. (2003) and Stein et al. (2000). The former

defined social anxiety groups through the cluster analysis of the situations of the Anxiety

Disorders Interview Schedule-Revised (ADIS-R) (Di Nardo & Barlow, 1988). The latter,

however, proposed a quantitative criterion based on the DSM-IV criteria (especially concerning

the conceptualization of generalized social anxiety as the ‘‘fear of most social situations’’). It

included people in the category of generalized social anxiety when they expressed fear of 7 or

more social situations out of 12 (half of them were performance situations, whereas the other half

were interactional situations) and in another non-generalized group, which comprised the rest of

individuals. Heimberg and Holt (1989) classified social phobia subtypes into three kinds:

generalized (defined as the fear of most social situations), circumscribed (fear of a limited

number of discrete situations) and non-generalized (fear of a limited number of social interaction

situations with or without fear in specific performance situations). Likewise, Furmark et al.

(2000) clearly distinguished between a generalized subtype (with high scores), a non-generalized

subtype (with medium scores) and discrete social anxiety (with low scores).

In short, based on the previous studies we cannot talk about clearly differentiated social

anxiety categories in the general population, although such distinction between subtypes can be

used in the clinical practice. Moreover, it must be pointed out that most of the above-mentioned

studies were carried out on the adult population, whereas research on adolescents is still very

scarce.

5. Conclusions

The review of the psychometric properties of the SIAS must explore its items separately in

order to obtain information about their character and features. It would also be convenient to add

more items to the SIAS scale, especially positively worded ones. The reason for this is that it

currently includes only three items of this kind, which show very low correlations with the

remaining items and low reliability. Therefore, future studies should focus on modifying this

scale, formulating new positively worded items that belong to a possible second dimension and

leading to new studies that aim at reviewing the psychometric characteristics of the SIAS.

Likewise, the factor analysis of the SIAS should be made with the 20 elements it contains in order

to obtain evidence on the possible bidimensionality or tridimensionality of this scale, given that

the confirmatory factor analysis rejects the single-factor model put forward by the original

authors of the scale. Moreover, the SIAS seems to assess specific dimensions that differ from the

social anxiety construct, which highlights the complexity of the construct measured. Such

dimensions may refer to anxiety experienced by people due to the lack of social skills, to the

possible inadequate estimation of emotional distance with respect to others, and to the discomfort

experienced in social interaction situations. Along these lines, it is expected that the SIAS will

correlate significantly with different variables related to the field of interpersonal relations,

especially with those related to social anxiety and avoidance. Future studies would then identify

these possible dimensions in populations of adults and adolescents.

Apart from this, it seems, the distributions of the SIAS scores does not show one single

population, but rather mixed populations where different groups can be distinguished. The

distinction between the possible groups always depends on the separation criterion used and

applied by each researcher depending on his or her interests and objectives. Thus, it is possible to


determine social anxiety subtypes with the SIAS scale by applying mainly quantitative criteria,

although quite often the distinction between groups is not completely clear. Perhaps future

studies should consider not only quantitative but also qualitative criteria when establishing

groups with specific and generalized social anxiety that differ from other groups without social

anxiety for both the adult and adolescent populations.

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