Hi Guilia,

here is an old but apparently still valid scale for the purpose in question:

The SPQ: A Scale for the Assessment of Schizotypal Personality Based on DSM-III-R Criteria.

Raine, Adrian

Schizophrenia Bulletin, Vol 17(4), 1991, 555-564.

Abstract

Existing self-report measures of schizotypal personality assess only one to three of the nine traits of schizotypal personality disorder. This study describes the development of the Schizotypal Personality Questionnaire (SPQ), a self-report scale modeled on DSM-III-R criteria for schizotypal personality disorder and containing subscales for all nine schizotypal traits. Two samples of normal subjects (n = 302 and n = 195) were used to test replicability of findings. The SPQ was found to have high sampling validity, high internal reliability (0.91), test-retest reliability (0.82), convergent validity (0.59 to 0.81), discriminant validity, and criterion validity (0.63, 0.68), findings which were replicated across samples. Fifty-five percent of subjects scoring in the top 10 percent of SPQ scores had a clinical diagnosis of schizotypal personality disorder. Thus, the SPQ may be useful in screening for schizotypal personality disorder in the general population and also in researching the correlates of individual schizotypal traits. (PsycINFO Database Record (c) 2013 APA, all rights reserved)

 here is a link too:

Wisconsin Card Sorting Test deficits in schizotypic individuals

By: Diane C Gooding, Thomas R Kwapil and Kathleen A Tallent

Gooding, D.C., Kwapil, T.R., & Tallent, K.A. (1999). Wisconsin card sorting test as a vulnerability marker in schizotypal individuals. Schizophrenia Research, 40, 201-209. http://dx.doi.org/10.1016/S0920-9964(99)00124-3

http://libres.uncg.edu/ir/uncg/f/t_kwapil_wisconsin_1999.pdf

Abstract:

The present study investigates executive functioning in schizotypic college students and control subjects using the Wisconsin Card Sorting Test (WCST). Inhibitory control and working memory, two aspects of executive functioning, were examined in deviantly high scorers on the Perceptual Aberration and Magical Ideation Scales (n=97), high scorers on the revised Social Anhedonia Scale (n=58), and in control subjects (n=104). The schizotypic groups displayed significantly more perseverative errors and achieved fewer categories than the control group. The two schizotypic groups did not differ from each other. We identified a subset of schizotypic individuals who also produced clinically deviant WCST profiles. The findings support the hypothesis that executive function deficits may precede the onset of schizophrenia and related illnesses.

Kwapil, T.R., Gross, G.M., Silvia, P.J., & Barrantes-Vidal, N. (2012). Psychometric properties and validity of short forms of the Wisconsin Schizotypy Scales in two large samples. Presented at the 2012 meeting of the Schizophrenia International Research Conference, Florence, Italy.

Rosa, A., Moreno, A., Ros-Morente, A., Kwapil, T.R., & Barrantes-Vidal, N. (2012). COMT Val158Met genotype and schizotypy dimensions. Presented at the 2012 meeting of the Schizophrenia International Research Conference, Florence, Italy.

Barrantes-Vidal, N., Lewandowski, K.E., & Kwapil, T.R. (2010). Correlates of schizotypy clusters in a large non-clinical sample. Presented at the 2010 meeting of the Schizophrenia International Research Conference, Florence, Italy.

Look up these researchers here on RG.

Please note that the "Wisconsin schizotypy scales" are more accurately referred to collectively as the Chapman psychosis-proneness scales, and individually, there are several: Perceptual Aberration scale, Magical Ideation scale, revised Social Anhedonia scale, and revised Physical Anhedonia scale.  They're usually administered in an intermixed format, along with an infrequency scale to detect random response patterns.  Schizotypal personality disorder is a diagnostic category, whereas schizotypy is a latent personality construct/trait, so you may wish to consider the advantages & disadvantages of relying on the SPQ for your purposes.   If you contact me, I'd be happy to provide more information.  Good luck with your research!

You can also use the Schizotypyal Personality Questionnaire: B which is a shorter version. You can still get a total score and the three subscales of cognitive-perceptual, interpersonal and disorganised symptomatology.http://guilfordjournals.com/doi/abs/10.1521/pedi.1995.9.4.346

Adrian Raine's scale is well respected. I'm attaching a copy of the original article, which appeared in Schizophrenia Bulletin.

The "Chapman Scales" are also well regarded. They were based on Meehl's theoretical model, positing schizotypy as a necessary precondition for schizophrenia. (You can find his original Manual for Checklist of Schizotypal Signs on line.) Originally called the Wisconsin Scales for Psychosis Proneness, they were developed piecemeal (i.e., a given graduate student would develop and validate one as his/her dissertation project) and intended for use in "high risk" research. The idea here is that people who display certain features (schizotypy, if you like) are at elevated risk of developing frank psychotic symptoms, therefore worth studying and following up. Although technically these are not intended to measure the DSM diagnosis, that diagnosis was based squarely on Meehl's work. I'm also attaching a copy of a document that includes the Chapman Scales with some normative data. The two that have attracted the most attention are the Perceptual Aberration Scale and the Magical Ideation Scale.

A third possibility would be the Psychoticism scale from the Eysenck Personality Questionnaire. This has a somewhat different theoretical angle, and the content is less obviously related to the DSM personality disorder, but it is an important resource to be aware of - for your literature review, if nothing else.

Oliver Mason (who worked under Gordon Claridge, I think) also developed a set of scales. I don't know how widely they have been used, but I'm attaching that paper as well.

There are also (1) a Personality Disorders Questionnaire intended as an aid to DSM diagnostic interviewing, (2) a set of MMPI scales for personality disorders developed by Tom Widiger, and last but not least, (3) Ted Millon's Multiaxial Clinical Personality Inventory (MCMI-III). The MCMI-III is widely used clinically; Millon was one of the architects of the DSM personality disorders section back in the day.

So what with one thing or another, you've got plenty of options. Unfortunately I have no idea how many of these have been translated into Italian. My guess is that some of the Chapman scales have been, but that's just a guess.

I would agree with Karen, SPQ short version seems the best.

SPQ is the best one, definitively.

Note that scale selection also depends on the population and symptoms of interest. I like the Structured Interview for Schizotypy (SIS) (Kendler et al, 1989). It covers schizotypy as well as paranoid and schizoid PD. The SIS provides a more detailed assessment of negative schizotypal symptoms compared to the SPQ. (This is especially important for genetic liability research - i.e. assessment of relatives of patients with schizophrenia-spectrum disorders vs. psychosis-proneness/schizotypy in general population samples.) The SIS takes about 15-20 minutes to administer and generates ratings based on the subject's responses during the interview as well as ratings based on interviewer observation - a useful component if reliability/bias of subject report is of interest.

If you have time and willingness to invest effort, a semi-structured interview would be a good idea, as Dr. Tarbox suggests. Among the self-report measures, Olson's was actually developed in the context of genetics research - validated using heritability coefficients from twin studies.

Just a suggestion. If the aim of the study is to investigate the link between personality traits and internet addiction, impulsivity could be assessed. UPPS impulsive behavioral scale is a relevant scale for impulsivity assessment (Whiteside & Lynam, 2001).

As for SPQ and its italian version, these could be of help:

Schizotypal personality questionnaire and wisconsin card sorting test in a population of DSM-III-R schizophrenic patients and control subjects (1998)

E Daneluzzo, M Bustini, P Stratta, M Casacchia, A Rossi

http://www.sciencedirect.com/science/article/pii/S0010440X98900736

The three-factor model of schizotypal personality: invariance across age and gender (2003)

Andrea Fossati, Adrian Raine, Ilaria Carretta, Barbara Leonardi, Cesare Maffei

http://www.sciencedirect.com/science/article/pii/S0191886902003148