The cognitive approach is the dominant approach in modern psychology. The study of the physical world and the mental world and the differences between them was starting point for cognitive psychology. In some early experiments, Gustav Fechner (1801-87) was able to demonstrate some of these differences. For example, he investigated how much louder a sound had to be, compared with the original sound, before a person would perceive it as twice as loud. Fechner discovered that the sound had to approximately eight times greater before it was perceived as twice as loud. Obviously, the physical sensations created by stimuli impinging on the sense organs are only the first steps in how we come to experience our world.
According to Wilhelm Wundt (1823-1920), psychology was the study of immediate experience, and that excluded any consideration of cultural or social interpretations. Early proponents of the cognitive approach (such as Miller et al. 1960) pointed out that behavioural accounts were inadequate because they say nothing about how people process information. Cognitive psychologist, on the other hand, went on to propose models of human thought and problem solving (e.g. Newell and Simon 1972). These advances continue today. Cognitive psychology has helped explain many aspects of everyday behaviour and experience, e.g. why we forget things, why eyewitness testimony is often inaccurate and why we experience visual illusions. By applying knowledge from cognitive psychology, we can improve our performance in many areas.
Cognitive psychology has influenced and integrated with many other approaches and areas of study to produce, for example, social learning theory, cognitive neuropsychology, and artificial intelligence. Cognitive psychologists assume that mental processes can and should be investigated scientifically. The belief of cognitive psychologists is that humans are not merely passive renders to their environment. One of weaknesses of the cognitive approach is its failure to address everyday behaviour and experience.
Wundt set the agenda for ignoring social and cultural variables and although some cognitive psychologists have shown the importance of these variables (e.g. Bartlett 1932, Deregowski 1972) they do not form part of the general debate in cognitive psychology. The cognitive model like behaviourism has been accused of being over simplistic, it is said to ignore the complexity of human functioning compared to computer functioning. To put it one way, just it walks like a duck and quacks like a duck does not mean that it really is a duck. There is more to a duck than walking and quacking. Therefore, to date, the computer metaphor remains an inadequate way of modelling human cognitive processes.
This model has also been accused of being to unrealistic and over hypothetical because of the lack of attention paid to biological influences and grounding mental processes. Another accusation would be how the model seemingly ignores the emotional life of humans, their conscious experience and possible use of freewill. The strengths of the most dominant approach today are that investigates many areas of interest in psychology that had been neglected by behaviourism; yet unlike psychoanalysis, it investigates them using more rigorous scientific methods.
The approach has provided explanations of many aspects of human behaviour and has had useful practical applications it has also combined with other approaches to strengthen its explanations and usefulness, e.g. cognitive neuropsychology. Consequently, I can conclude that Cognition although possibly ignoring factors that need attention has proved to be easy to human behaviour therefore making it a strong contender in the battle for dominant and applications to psychology.
My conclusions are simple I, personally believe that it is possible to use every one of the approach of psychology to make a final definition of the term. To leave any approach out the explanation would make your definition less valid and factual, I myself have failed to mention to two of the main approaches, Humanism (looking at our previous experiences) and Biological (looking at what we are made of), due to lengthy description and analysis I have gone into of each approach. There are many more approaches, not ignored or any less important than the others-evolutionary, structuralism etc which are perhaps not as popular or as mentionable as the others but that could still be use to define the term, psychology.
The reason some choose to apply, develop and quote some approaches rather than others is due to personal opinion rather than one being considerably better than the other. Each have approximately the same amount of strengths and weaknesses as the other therefore it is not possibly to claim one as being officially the best approach. I personally do not have a preferred perspective, and if asked to explain psychology I would quote from each model as I feel each helps enlighten to as what psychology is about. Consequently I can conclude that to define psychology I do not feel it possible to use one quote, statement, theory or idea and each and every theory will add to a section of your explanation of what is the complex subject we call Psychology.