Perceptual, cognitive, and motor resources can be occupied in parallel during skilled performance

What it is

CPM-GOMS models skilled execution as parallel activity across perceptual, cognitive, and motor processors: while the hand moves to the mouse, the user may continue reading status; while the system responds, the next step is being planned; while speech is produced, the eyes search for the next item.

Why it happens

Parallelism is constrained rather than unconditional. One motor effector cannot perform two acts, visual fovea is limited, and working memory determines how many subgoals can be held; nevertheless, different channels and automated segments can overlap. The model labels each activity with processor, start condition, duration, and dependencies to reveal genuine overlap and conflict.

Studying it

Align event times using high-frame-rate video, eye tracking, input logs, and verbal protocols; decompose actions into perceptual, cognitive, and motor processors with dependencies. Compare parallelism across proficiency groups or use dual-task paradigms to test resource conflict. Model parameters should come from target users and devices.

Where it stops holding

Parallel does not mean simultaneous for every operation; errors, interruption, and novel interfaces break automation. Resource models are approximations, not neural mechanisms. For infrequent tasks, begin with serial KLM or GOMS.

Applying it

• Draw a parallel timeline for frequent tasks, marking perception, cognition, motor, and system response.
• Find overlap opportunities: show the next step during waiting, allow confirmation during speech, preload during hand movement.
• Avoid competition on the same channel, such as voice masking a critical visual state.
• Validate parallel assumptions with skilled users rather than generalizing from novices.

Related

• Same group: B4.13.2 Total time is determined by the critical path, not the sum of all operation times · B4.13.3 Shortening an operation off the critical path does not change total time · B4.13.4 The model applies only to highly skilled performance; novice behavior is not parallel · B4.13.5 Critical-path analysis explains why removing steps did not make the task faster
• Nearby: B4.04 GOMS · B4.05 Keystroke-Level Model
• Search terms: CPM-GOMS · parallel operators · cognitive resources