Being shy is not the same as being scared
Someone can present to a room of two hundred people without much trouble and then freeze at a friend's birthday party. That split is why Mattick and Clarke built two scales instead of one. The Social Phobia Scale covers the fear of being watched while doing something ordinary: eating, drinking, writing, signing your name. The Social Interaction Anxiety Scale (SIAS) covers the other half, the fear of meeting and talking with people, which is the part that maps onto the generalised form of social phobia.
This page is about the SIAS. It asks about conversations, not performances.
What the 20 items ask
Every item is a statement, and you rate how much it describes you: not at all characteristic, slightly, moderately, very, or extremely. The total runs from 0 to 80, and higher means more distress in social interaction.
The items came out of a long selection process. The authors started with a pool of 164 statements, cut it to 79 for content validity, had four independent raters sort them by construct, and ended up with 38 social interaction items. Item analysis then removed 19 more, leaving 19 items in the version reported in the 1998 paper. The 20-item form in circulation today adds one item, and this site uses that version.
Three items are worded in the confident direction (5, 9 and 11), covering making friends, being at ease at parties, and finding things to talk about. They are reversed before the total is summed, so that ease lowers the score rather than raising it.
One factor, and a known flaw in it
The scale is meant to measure a single construct, and the original factor analysis supported that: one factor with an eigenvalue above 1 accounted for 43.4% of the variance, with everything else adding only 8.3%. Seventeen of the 20 items loaded above 0.40 on it.
The three reversed items are the weak point. Rodebaugh, Woods and Heimberg (2007) found that they correlated with extraversion more than with social anxiety, that they behaved differently from the other items against comparison measures, and that dropping them tends to help rather than hurt the psychometric performance of the total score. Their recommendation for research is to analyse the 17 straightforwardly worded items. This site keeps all 20, since the reversed items do break up a pattern of agreeing with every statement, but it is worth knowing that the reversed trio measures something slightly different.
How scores compare with other groups
The 1998 paper reports means across five samples. These come from the 19-item version, so a 20-item score runs up to four points higher at the top of the range.
| Sample | N | Mean | SD |
|---|---|---|---|
| Social phobia | 243 | 34.6 | 16.4 |
| Agoraphobia with panic | 13 | 26.0 | 13.6 |
| Simple phobia | 16 | 14.8 | 12.2 |
| Undergraduates | 482 | 19.0 | 10.1 |
| Community adults | 315 | 18.8 | 11.8 |
Two things stand out. Students and community adults land in the same place, around 19, which suggests the scale is not simply picking up being young or being busy. And the gap between the social phobia group and everyone else is wide enough that the scale separates the groups rather than just ranking distress.
Cutoffs
The commonly used threshold is a total above 36, taken from the PsyPack guidance (Peters, 2000). A Swedish validation of the two companion scales put the optimal cutoff lower, at 22, when separating people with social anxiety disorder from controls. That is a wide spread, and it reflects the usual problem with screening cutoffs: a lower threshold catches more cases and produces more false alarms.
The bands this site reports:
| Total | Reading |
|---|---|
| 0 to 36 | Low to moderate social anxiety |
| 37 to 42 | Just past the common cutoff |
| 43 to 80 | High social anxiety |
The middle band is deliberately narrow. It marks the zone where the total sits close to the line and the reading depends on how much the pattern interferes with your life, which no cutoff can measure.
Reliability and what it tracks
Internal consistency was 0.93 in the social phobia sample, 0.91 in the agoraphobia sample, 0.92 in the simple phobia sample, 0.88 in undergraduates, 0.90 in the community sample, and 0.94 across the pooled sample of 1,069 people. Test-retest correlations were 0.92 over four weeks and 0.92 over twelve weeks, which is high for a measure of anxiety.
On convergent validity, the SIAS correlated 0.72 with its sister scale, 0.74 with the Social Avoidance and Distress Scale, 0.66 with the Fear of Negative Evaluation Scale, and 0.66 with the social phobia subscale of the Fear Questionnaire. Depression correlated 0.47 on its own, but only 0.24 once fear of negative evaluation was held constant, which supports the authors' claim that the scale is not a disguised depression measure. Social desirability correlated 0.30, low enough that the scale is not mainly measuring how much you want to look good.
The scale also moves when it should: scores dropped after treatment in treatment-outcome studies and stayed flat in the waiting-list group. One more detail from the original paper, useful if you retest: SIAS scores correlated negatively with age, at 0.38, meaning older respondents reported less interaction anxiety on average.
Take the test
The CheckPsych version uses the 20 items and takes about 5 minutes. You get a total between 0 and 80, a band, and a short reading of what it suggests. A high score is not a diagnosis of social anxiety disorder. It means social situations cost you more than they cost most people, and if that cost is shaping what you avoid, treatment for social anxiety has good evidence behind it.
References
Mattick, R. P., & Clarke, J. C. (1998). Development and validation of measures of social phobia scrutiny fear and social interaction anxiety. Behaviour Research and Therapy, 36(4), 455-470.
Rodebaugh, T. L., Woods, C. M., & Heimberg, R. G. (2007). The reverse of social anxiety is not always the opposite: The reverse-scored items of the Social Interaction Anxiety Scale do not belong. Behavior Therapy, 38(2), 192-206.
Mörtberg, E., et al. (2017). Factor solutions of the Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale (SIAS) in a Swedish population. Cognitive Behaviour Therapy.
Gholizadeh, S., et al. (2018). Validation of the Social Interaction Anxiety Scale-6 (SIAS-6) in systemic sclerosis (PMC).
Disclaimer: this article and the SIAS are for education and self-reflection. They are not a diagnosis or a treatment recommendation. Social anxiety responds well to cognitive behavioural therapy, and a score on a questionnaire is a starting point for that conversation rather than a conclusion. If anxiety about social situations is limiting your work, study or relationships, a qualified professional can help.