According to PASS model, theory based on information processing approach, intellectual activity involves the interdependent functioning of the three neurological systems called the functional units of the brain.

These units are responsible for:

• the arousal and attention.

• the simultaneous and successive processing.

• the planning.

Arousal and Attention:

(i) State of arousal helps in attending to the stimuli.

(ii) Arousal and attention enable a person to process information.

(iii) Optimal level of arousal focuses our attention on relevant aspects of a problem.

(iv) Too much or too little arousal interferes with attention and performance.

Example: Arousal helps the individual to focus ones attention on reading, learning and revising the contents of the material to be learnt.

Simultaneous and Successive Processing:

Simultaneous Processing refers to perceiving relations amongst various concepts and integrate them into meaningful patterns for comprehension. For e.g., in Raven's standard progressive matrices (RSPM Test) choosing appropriate pattern by comprehending relationship.

Successive Processing refers to recalling information serially so that one recall leads to another recall. For example, learning of digits and letters and multiplication tables.

Planning:

1. After the information is attended to and processed, planning is activated.

2. Planning involves reaching to the target and evaluating their effectiveness. Planning allows us to think of possible courses of action and implementing them.

3. If a plan does not work, it is modified to suit the requirements of the task or the situation.

4. For example, to take a test scheduled by your teacher, you'd have to set goals, plan a time schedule of studies, get clarifications in case of problems or think of other ways to meet your goals.