Thought processes

Thought processes: Cogito ergo sum (I think therefore I am). These words of Descartes sum up the importance of thought processes in humans and probably the most important reason we differ from animals. Although animals retrieve and store information, there is little evidence to suggest that they can use it in quite the same way as humans. Humans, on the other hand, are able to use information to reason and solve problems, even when the information is partial or unavailable.
Thinking can be categorized into reasoning and problem solving. Although these are not distinct they are helpful in clarifying the processes involved.

Reasoning: Reasoning is the process by which we use the knowledge we have to draw conclusions or infer something we know about the domain of interest. Reasoning is classified as being deductive, inductive or abductive. Deductive reasoning involves deciding what must be true given the rules of logic and some starting set of facts(premises). Inductive reasoning involves deciding what is likely to be true given some starting set of beliefs or observations.

Problem solving: Problem solving is the process of finding a solution to an unfamiliar task, using the knowledge we have. There are a number of different views of how people solve problems.

Problem space theory: The problem space theory was proposed by Newell and Simon. The theory says that problem solving centers around the problem space. This space comprises of problem states which can be generated using legal transition operators.
For example, imagine you are reorganizing your office and you want to move the desk from one end to another. The two different states are represented by the locations of the desk. A number of operators can be applied to move these things: they can be carried, pushed, dragged etc. In order to ease the transition between the states, you have a new sub-goal: to make the desk light. These may involve operators such as removing drawers and so on.
Within the problem space framework, experience allows us to solve problems more easily sice we can structure the problem space appropriately and choose operators efficiently.

Analogy in problem solving: People solve novel problems by mapping knowledge in a similar known domain, to it. For instance, to destroy malignant tumour it is essential to fire low intensity rays from all sides, as high intensity rays can damage heathy tissues. An analogous case is that of attacking a fortress. However, people miss analogous information unless it is semantically close to the problem domain.

Individual differences: The psychological principles and properties that have been discussed apply to the majority of people. However, there are individual differences which affect a small percentage. The differences may be long term such as sex, physical capabilities and individual capabilities. Others are for a shorter duration and may include the effects of stress or failure on the user. Still others may change through time such as age. These differences should be taken into account in interface designs to enusre that a greater population of users is benefited.