Cognitive psychology is an interdisciplinary field whose main aim is to study the thinking mechanisms of humans leading to cognizance. Therefore the concept of human cognitive processes envelopes the knowledge related to the mechanisms which determine the way humans acquire information from the environment and utilize their knowledge and experience. There are three basic processes which need to be distinguished when discussing human perception development: acquiring sensations, perceptiveness and attention. Acquiring sensations means the experience arising from the stimulation of a single sense organ, i.e. detection and differentiation of sensory information. Perceptiveness stands for the interpretation of sensations and may include recognition and identification of sensory information. The attention process relates to the selectivity of perception. Mental processes of the higher order used in cognition, thanks to which humans tend to try to understand the world and adapt to it, doubtlessly include the processes of memory, reasoning, learning and problem solving. There is a great difference in the human cognitive functioning at different stages of one's life (from infancy to adulthood). The difference is both quantitative and qualitative. There are three main approaches to the human cognitive functioning development: Jean Piaget's approach, information processing approach and psychometric approach. Piaget's ideas continue to form the groundwork of child cognitive psychology. Piaget identified four developmental stages of child cognition: 1. Sensorimotor stage (birth - 2 years old); 2. Preoperational stage (ages 2-7); 3. Concrete operations (ages 7-11; 4. Formal operations (11 and more). The supporters of the information processing approach use a computer metaphor to present the human cognitive processes functioning model. The three important mechanisms involved are: coding, automation and strategy designing and they all often co-operate together. This theory has provided a theory. The psychometric approach concentrates on studying the differences in intelligence. The aim of this approach is to test intelligence by means of standardized tests (e.g. WISC-R, WAIS-R) used to show the individual differences among humans. Human cognitive functions determine individuals' adaptation capabilities and disturbances in this area indicate a number of psychopathological changes and are a symptom enabling to differentiate or diagnose one with a disorder. That is why the psychological assessment of cognitive functions is an important part of patients' diagnosis. Contemporary neuropsychological studies are to a great extent based computer tests. The use of computer methods has a number of measurement-related advantages. It allows for standardized testing environment, increasing therefore its reliability and standardizes the patient assessment process. Special attention should be paid to the neuropsychological tests included in the Vienna Test System (Cognitron, SIGNAL, RT, VIGIL, DAUF), which are used to assess the operational memory span, learning processes, reaction time, attention selective function, attention continuity as well as attention interference resistance. It also seems justified to present the CPT id test (Continuous Performance Test) as well as Free Recall. CPT is a diagnostic tool used to assess the attention selective function, attention continuity of attention, attention interference resistance as well as attention alertness. The Free Recall test is used in the memory processes diagnostics to assess patients' operational memory as well as the information organization degree in operational memory. The above mentioned neuropsychological tests are tools used in clinical assessment of cognitive function disorders.