Problems of Forensic Sciences 2007 Vol. 69 (LXIX) 30-36
HANDWRITING OF MONOZYGOTIC AND DIZYGOTIC TWINS
Tomasz DZIEDZIC1, Ewa FABIAŃSKA1, Zuzanna TOEPLITZ2
1Institute of Forensic Research, Krakow
2Faculty of Psychology, University of Warsaw, Warsaw
Streszczenie
The issue of similarities in the handwriting of unrelated and related people holds a prominent position in the field of forensic handwriting examination. Similarities in the handwriting of related persons occur particularly often in the handwriting of twins, though the conformity is not strong enough to cause any serious difficulties in discriminating between the handwriting of individual twins within a pair. The matter, however, of the influence of mono- and dizygosity on the degree of similarity in their handwriting is still open to question. Therefore the objective of this research was to determine, whether in the handwriting of monozygotic (MZ or identical) twins there are more similarities than in the writing of dizygotic (DZ or fraternal) twins and what the distribution of common graphic features is in each of these groups. The analysis was conducted on writing and signature samples submitted by 54 pairs of twins, including 31 pairs of MZ and 23 pairs of DZ twins. Each individual wrote a short text, containing all the letters of the alphabet as well as submitting specimens of their usual signature. The collected samples were examined taking into account 32 features in total. Each feature’s degree of similarity was rated by two experts independently on a four-grade scale consisting of the following categories: “definitely different”, “rather different”, “rather similar” and “definitely similar”. In analysing the obtained results, an appropriate numerical value was ascribed to each category (–2, –1, 1 and 2, respectively) and then averages were calculated, defining the degree of similarity of handwriting within every pair of twins, and also averages defining the degree of similarity of a single feature in the handwriting of all the couples in each group (i.e. identical or fraternal twins). The examination revealed that differences predominated over similarities in both groups; nevertheless, in the group of MZ twins this predominance was slightly less. None of the examined features was rated as similar significantly more frequently in the group of monozygotic twins than in the group of dizygotic twins.
Słowa kluczowe
Handwriting; Family likenesses in handwriting; Similarity in handwriting; Twins.