Table 1.

Estimated Parameters Used in Model Human Processor (taken from Card et al., 1986)

Parameters of interest	Typical parameter estimates [lower and upper bounds]
Perceptual system-visual
Eye movement (travel + fixation)	230 [70–700] ms
Memory decay time (visual)	200 [90–1000] ms
Capacity (visual)	17 [7–17] letters
Cycle time (response time to brief pulse of light)	100 [50–200] ms
Perceptual system-auditory
Memory decay time (auditory)	1500 [90–0–3500] ms
Capacity (auditory)	5 [4.4–6.2] letters
Cycle time (time needed to differentiate fast clicks)	100 [50–200] ms
Motor system
Cycle time (time needed to perform a discrete micromovement, as assessed by tapping rates)	70 [30–100] ms
Cognitive system
Memory decay time (working memory-general)	7 [5–226] seconds
Memory decay time (WM-1 chunk)	73 [73–226] seconds
Memory decay time (WM-3 chunks)	7 [5–34] seconds
Storage capacity (pure working memory)	3 [2.5–4.2] chunks
Storage capacity (effective WM-augmented by LTM)	7 [5–9] chunks
Cycle time (time needed to match item against WM-calculated as typical value over many tasks (e.g. digits, colors, letters, words, shapes)-can be shortened by practice, task pacing, more effort, or reduced accuracy)	70 [25–170] ms