On the Discriminability of the Handwriting of Twins

Abstract

As handwriting is influenced by physiology, training, and other behavioral factors, a study of the handwriting of twins can shed light on the individuality of handwriting. This paper describes the methodology and results of such a study where handwriting samples of twins were compared by an automatic handwriting verification system. The results complement that of a previous study where a diverse population was used. The present study involves samples of 206 pairs of twins, where each sample consisted of a page of handwriting. The verification task was to determine whether two half-page documents (where the original samples were divided into upper and lower halves) were written by the same individual. For twins there were 1236 verification cases-including 824 tests where the textual content of writing was different, and 412 tests where it was the same. An additional set of 1648 test cases were obtained from handwriting samples of nontwins (general population). To make the handwriting comparison, the system computed macro features (overall pictorial attributes), micro features (characteristics of individual letters), and style features (characteristics of whole-word shapes and letter pairs). Four testing scenarios were evaluated: twins and nontwins writing the same text and writing different texts. Results of the verification tests show that the handwriting of twins is less discriminable than that of nontwins: an overall error rate of 12.91% for twins and 3.7% for nontwins. Error rates with identical twins were higher than with fraternal twins. Error rates in all cases can be arbitrarily reduced by rejecting (not making a decision on) borderline cases. A level of confidence in the results obtained is given by the fact that system error rates are comparable to that of humans (lower than that of lay persons and higher than that of questioned document examiners [QDEs]).KEYWORDS: forensic science, questioned document examination, handwriting processing, document analysis, writer verification, twins studyThe distinctiveness of each person's handwriting has long been intuitively observed. Methods have been developed for a human expertise of handwriting matching over many decades (1-5). Yet there is a need for studies in the quantitative assessment of the discriminative power of handwriting particularly for the acceptance by the courts of evidence provided by questioned document examiners (QDE). In a previous study of handwriting individuality (6), we reported on the discriminability of handwriting of a diverse population from across the United States. The present paper reports on a complementary study of the discriminatory power of handwriting when the population consists of a cohort group consisting of twins. Both the previous study and the current study are based on automated methods for handwriting comparison. The current study uses algorithms that are updated with respect to the types of handwriting features that are computed.The necessity of studying cohort groups such as twins has been considered to be i...

A Study to Determine the Inheritance Pattern of Characteristics of Handwriting between Parents and Off-springs

“…Apart from these, the characteristics such as alignment (79.16%), shading (79.16%) and connecting stroke (77.08%) also show a high level of similarity [15]. However, there was only 29.16% similarity found in pressure applied while writing.…”

Tek yumurta İkizlerinin El Yazılarının Adli Belge İncelemesi Açısından Değerlendirilmesi

“…(2008) tarafından yapılan benzer bir çalışmada incelenen 206 ikiz çiftinin el yazısının ayırt edilmesi amaçlanmış, elde edilen sonuçlar ikiz olmayan bireylerin el yazısıyla karşılaştırılmıştır. Araştırmanın sonucunda, ikiz çiftlerin el yazısı birbirinden ayırt edilebilmiş ancak oransal başarı düzeyi ikiz olmayanların el yazısına kıyasla daha düşük seviyede olduğu bildirilmiştir (18). İncelenen metin içerisinde "a, b, d, g, m, r, ş, u, v, y, z" harflerinin çiftler içinde kullanımındaki benzerlikler; erkek ikiz çiftlerde, kadın ikiz çiftlere oranla daha az gö-rülmüş olup, ikiz erkek çiftlerin en çok benzer kullandık-ları harfler sırası ile "d, v-z, y-r-b, v, a, ş, g-m" iken, ikiz kadın çiftlerde bu sıra şu şekildedir; "r, b-d, v, y, z-u, a, ş, g, m'.…”

Evaluating the Rarity of Handwriting Formations

“…However there have been very few efforts to characterize the statistical characteristics of such features, most notably [4]. On the other hand there have been efforts to compute features automaticallybut the features tend to be gross approximations of the characteristics employed [5], [6] or the features do not correspond to human determined characteristics at all [7], [8].While these automated methods perform well in objective tests they do not lend support to the document examiner in testimony. Our goal here is to capture the statistics of document examiner specified characteristics so that a probability statement of rarity can be made as in other forensic domains.…”