CPS 613 – 2-3
HUMAN INFORMATION PROCESSING STAGES
Stages
Stage 1: Encoding
 Encoding information from the environment into some form of internal
representation
 Humans interact with computers with their senses: sight, hearing, and touch.
Smell and taste are not used.
Stage 2: Comparison
 Internal representation compared with memorized representations
Stage 3: Response Selection
 Deciding on a response
Stage 4: Response Executions
 Organisation of response and execution
1
CPS 613 – 2-3
HUMAN INFORMATION PROCESSING STAGES
2
Goal: make user effective.
Effectiveness
 Effectiveness = Speed + Correctness/Accuracy
 Both are a function of age, fitness, skill, fatigue of the user, which cannot be
controlled. U.I. can be controlled though.
Speed:
 time broken down into:
reaction time (1) + thinking time (2-3) + movement time (4)
 Reaction time is a function of sense through which stimulus is received:
- auditory signals perceived faster than visual signals, faster than pain
signals.
- More than one sense  faster.
 Movement time function of distance of object: closer = easier to get to
Accuracy: (4)
 Hitting correct target
 Not necessarily inversely related to speed
 Function of size of object: bigger = easier to “hit”
Fitt’s Law
 T is the average time taken to complete the movement.
 a and b are model parameters.
 D is the distance from the starting point to the center of the target.
 W is the width of the target measured along the axis of motion. W can also be
thought of as the allowed error tolerance in the final position, since the final
point of the motion must fall within ±W⁄2 of the target's center.