Human personality has been continuously investigated as a configuration of traits that reflect an individual's way of acting, feeling, thinking and adjusting to the environment. The continous process of understanding human nature and nurture is vital for predicting an individual's way of acting in specific contexts and in different life areas such as work field, social interactions, family functioning or attitudes towards health. Psychological research is making progress in linking personality traits with specific actions and behaviors (e.g. Eysenck, 1991; Gray, 1987, 1991; Watson & Clark, 1992), looking for individual differences in brain anatomy and physiology, in bodily functions and self-regulation processes, in sensation and perception, in information processing and thinking styles, in behaviour and emotion regulation, in interpersonal interaction and so on (e.g. Bandura, 2006; Block, 2002). Using biological (e.g. Nebylitsyn ''i Gray 1972) and physiological data (e.g. Fowles, 1980; Carver ''i White, 1994; Crider, 2008), the connection between human personality traits and behaviour are currently investigated through individual differences in brain functioning (Canli, 2006). A recent cybernetic model of global personality traits is examining how specific personality traits exert control over human behaviour (Van Egeren, 2009; Wiener, 1948). These traits are seen as self-regulatory controls that underlie behavior patterns rather than manifest behavior itself (Crider, 2008). It seems that human beings mentally incor''porate propensities of action into personality traits (Carver, 2005; Robins et al., 1996, Schneirla, 1959). These traits encode all the actions and controls necessary for a person to achieve a goal.
Although research in the field has made significant progress in explaining how personality and individual differences impact a person's behaviour and adjustment to specific contexts, measuring these aspects of personality is far more complicated. Almost every field of applied psychology requires psychological assessment tools. In order for psychologists and specialists to play their key part in improving individual and group functioning, at almost every level, they need to rigorously assess the individual, the group of people or the organization they are working with.
The development of mathematical models and advanced processing methods based on neural networks, especially those used in cognitive systems psychology , or other advanced methods of real time analysis for functions with several variables, has led to the increasingly visible affirmation of the important role that engineering plays in psychological research. To highlight this reality, it is interesting to follow the implementation aspects of medicine, which provide instruments for diagnosis and treatment, or development and therapy, respectively. In this regard, implementation involves the transposition of phenomenology in a method or tool, a definite appeal to engineering, because medical engineering, for example (also called bioengineering or biomedical engineering), interdisciplinary integrates professional activities of engineering with basic medical knowledge on the human body, as well as an understanding of how it works when healthy, sick or injured.
When studying the processes of perception, sensation, thinking, learning, and cognition, emotions and motivations, personality, behavior, interactions between individuals and interactions with the environment etc., psychology will have allied disciplines such as anthropology and sociology (in preoccupations regarding social and environment influences on behavior), physics (in addressing vision, hearing and touch), biology (in the study of the physiological bases of behavior) etc.
Diagnosis in psychology is circumscribed to psychometrics as a field concerned with theory and technique of psychological measurement. Psychometrics is one of the main branches of psychological cybernetics. Being focused on measuring the results of scientific activity, it deals with the quantification of mental phenomena and intellectual capacities, using standardized and calibrated experimental methods. Therefore, it builds measurement tools and procedures, it develops and refines theoretical approaches of measurement, necessarily relying on extensive implementing activity that makes the evaluation technologies available to the psihometrician psychologist and beyond. The connection between a specific technology and the way to turn it into a testing instrument involves much more than psychology.
Just like in medicine, in psychology, implementation of a phenomenon in order to use it in a testing equipment involves the interdisciplinary integration of basic psychological knowledge regarding the human being, with professional engineering activities and an understanding of the difference between normality and pathology. This is the role of psychological engineering, concerned with studying the phenomenon, analyzing its relationship with the psychometric purpose of testing, establishing the type of model approach, establishing the relationship between the dependent and independent variables (in the case of statistical models), and creating an algorithm which will then be implemented in a specific and advanced testing equipment. Therefore, psychological engineering appeals to cybernetic modelling by formalizing a part or a whole psychological system and by developing theoretical models that treat it as a cybernetic system, thus resolving the functional relationship provided by psychometrics, relationship that involves understanding and applying a manifest mental phenomenon, and approaching specific mental aspects through quantification and assessment. As the concrete result of a complex engineering endeavor in the field of psychology, the psychometric system MindMiTM combines sensitive aspects of recent theories on personality and behavior analyzed from a biological model perspective, using the benefits of an inventive implementation based on the electrodermal response technique, solving the inferential equation all the way with experimentally confirmed results. Modern theories in the psychology of personality and behavior Exploring the autonomic and somatic motor aspects of cognitive functioning has a long history in the field of psychophysiology and has acquired a similar application in neuropsychology and cognitive neuroscience research (Cacioppo et al, 2000; Sarter, Berntson & Cacioppo, 1996). Psychophysiological evaluation in normal and clinical population has contributed to the understanding of a wide range of relevant phenomena such as visual perception (Bauer, 1984; Tranel & Damasio, 1985), memory (Diamond, Mayes, & Meudell, 1996; McGlinchey Berroth, Carrillo, Gabrieli, Brawn, & Disterhoft, 1997), emotion (Bradley & Lang, 2000; Davidson & Sutton, 1995; Tranel & Hyman, 1990), or decision-making mechanisms (Bechara, Tranel, Damasio & Damasio, 1996). Organism-environment interactions may undergo a wide range of measurement methods, including electrodermal reactivity, pupillary responses, electromyographic changes, cardiovascular changes and their effects on hormonal and endocrine regulation (Schink, Velicer, & Weiner, 2003).
One of the most widely accepted theories regarding a biological model in psychology is the biopsychosocial personality theory, proposed by Gray in 1970. Eysenck and Gray were among the first researchers who studied personality traits through their relationship with individual differences in brain functioning. They assumed that brain processes can be described under the umbrella of a conceptual nervous system, comprising key circuits that are relevant to personality and behavior (Matthews, & Gilliland, 1999). Thus, empirical associations between personality and behavior can be derived from individual differences in brain functioning parameters. Eysenck took the biological personality traits into account and proposed the cortical arousal theory. He compared the level of arousal (physiological activation) with a scale of introversion - extraversion and used them to describe individual personality types and their corresponding behavioral patterns. Gray's theory began as a modification of Eysenck's theory and is more strongly anchored in physiological responses, having a strong scientific support from animal studies targeting different areas of the brain involved in different learning mechanisms (Canli, 2006). Gray proposed two control systems of behavioral activity (Gray, 1982, 1985a,b): the behavioral inhibition system and the behavioral activation system.
The behavioral inhibition system is a neuropsychological system related to sensitivity to punishment and aversive (avoidance-related) motivation, which inhibits motor behavior (Fowles, 1980). This system is recognized for its attempt to relate pharmacological, neuroanatomical, neurophysiological and behavioral aspects in one theory. According to Gray, the behavioral inhibition system has its neural bases in the septal area of the limbic system and in the hippocampus (the septo-hippocampal system and its interconnected structures). The theory assigns functions to each area of the system and to the ascending noradrenergic pathways afferent to these areas (Puente & McCaffrey, 1992).
The behavioral activation system corresponds to sensitivity to rewards and appetitive (approach-related) motivation, being related to the individual's disposition of pursuing and achieving his goals. The BAS initiates behavior in response to the stimuli conditioned for reward (approach-related), or to avoid punishment (active avoidance). The physiological mechanism for BAS is associated with the catecholaminergic and dopaminergic pathways in the brain.
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