Diferencias individuales en los perros domésticos (Canis familiaris): Revisión de las evaluaciones conductuales / Individual differences in domestic dogs (Canis familiaris): A behavioral assessment review

RESUMEN

El estudio de las diferencias individuales en el comportamiento de los perros domésticos tiene un gran valor aplicado dado que permite una mejor selección de los mismos para cumplir las variadas funciones que tienen en la sociedad humana como perros guía, policía, compañía, rescatistas de personas, etc. En el trabajo que se informa se presenta una revisión de estudios sobre diferencias individuales en perros, basada únicamente en las baterías conductuales que evalúan un conjunto de rasgos del temperamento. Con este objetivo se realiza una breve descripción de cada batería de pruebas utilizadas en la literatura, analizando las definiciones operacionales de las variables evaluadas y los diferentes tipos de estímulos utilizados. Los rasgos mayormente evaluados son temerosidad, agresividad, disposición al entrenamiento y sociabilidad. La temerosidad, en general es evaluada a través de la respuesta del animal ante la aparición de un estímulo súbito que puede ser intenso o no, como por ejemplo la reacción frente a un ruido fuerte, la apertura de un paraguas, o la aparición repentina de una figura humana. La agresividad se mide a través de la reacción frente a la amenaza o provocación por parte de un humano, la sustracción de un objeto o la confrontación con un perro dominante. La disposición al entrenamiento es estudiada a través de la respuesta del animal frente a diferentes estímulos como el juego con un trapo o una cuerda, el ejercicio de devolución de un objeto o la obediencia frente a distintos comandos. Por último, la sociabilidad se evalúa con la aparición o el acercamiento de un humano desconocido o con la exposición a un perro no familiar. Se discuten además las limitaciones metodológicas de las baterías así como también los importantes usos aplicados de las mismas.

ABSTRACT

A review of the research on individual differences in domestic dogs is presented in this paper. Temperament has been defined as the group of individual differences in behavior which is manifested steadily across situations and over time. It has been studied in a wide range of species including humans. Domestic dogs have undergone intense processes of selection on behavioral traits during domestication, and in the development of different breeds. These processes produced a great morphological, genetic and behavioral variability, which turned the dog in an interesting model for the study of individual differences. In this study we present a review of the different test batteries developed for the assessment of various behavioral traits. Test batteries are defined as standard experimental situations where a stimulus is used to provoke a behavior which is compared statistically to that of other individuals in the same situations, in order to classify the subjects. To achieve this aim, a brief description of seven batteries is given. Four of them evaluated dogs from breeding or train ing centers. Their aim was to select those animals which possess the most adequate traits to become guide or police dogs. The remaining batteries evaluated shelter dogs in order to elaborate a behavioral profile to improve the adoption process. In each battery described we analysed the operational definitions of the variables, the method used for scoring the animal's responses (overall vs. direct), the use of trained observers and the different types of stimuli used. The behavioral traits that are mainly assessed in dogs are fearfulness, aggressiveness, responsiveness to training, and sociability. Fearfulness is generally assessed through the appearance of a startling stimulus, which can be intense or not, such as the reaction towards a strong noise, the open ing of an umbrella, or the sudden appearance of a human figure. Aggressiveness is measured through the reaction towards a threat or provocation of a human being, the removal of an object, or the confrontation with a dominant dog. Responsiveness to train ing is studied through the response of the animal towards different stimuli, such as tug of war, retrieval, or obedience to commands. Finally, sociability is assessed with the appearance or approach of an unknown human being, or with the exposure to an unfamiliar dog. On the whole, the relevance of the assessment of these traits is fundamentally linked to the close relationship between dogs and humans. On the other hand, from a methodological point of view, it is important to note that most of the batteries evaluated a great number of subjects, which is difficult to achieve. Also, they allow to study behavioral variability in several traits at the same time, providing a large amount of information. Notably, several tests obtained predictive validity. The main difficulties presented by the temperament batteries are the diversity in nomenclature of the same traits and the variety of definitions used. Some of them even lack the reliability and validity requirements which are necessary to be considered measuring instruments. Furthermore, complex statistical analyses are done with unreliably obtained data. To conclude, despite the methodological limitations, temperament batteries have a great applied value. They allow the adequate selection of animals before the investment of valuable resources in their training, and a correct temperament evaluation can improve the adoption process of shelter dogs, diminishing the risk of relinquishment by predicting behavioral problems. The scope of this subject does not only matter to researchers interested in animal models of individual differences in behavior, but also to all the professionals who work in applied areas where dogs are an elemental part of the task, as the rescue or search of missing people, assisted therapy, drug detection, herding, etc.