Model Human Processor (MHP)

Definition of Model Human Processor (MHP)[1]

The Model Human Processor is a model of a series of information flows in a human from the viewpoint of information processing (Fig. 1). In the model, sensory information is input to perceptual processor, and then processed in cognitive processor, and finally an action is output through the motor system by motor processor.

Model Human Processor
Figure 1. Model Human Processor
source: Procedia

The processing time in each processor and the storage capacity of each memory is indicated in the model. Each processing time of each processor is as follows. The perceptual processor is 100ms. The cognitive processor is 70ms. The motor processor is 70ms. Using every processing time, the model estimates reaction time from the input of the sensation information to the action output through the motor system (Fig. 2). In the Model Human Processor, human reactions are classified into four cases according to the number of times of processing by the cognitive processor. The four cases are Simple reaction, Physical collation reaction, Name collation reaction and Category collation reaction.

MHP Reaction Time
Figure 2. Information processing model for estimation of reaction time
source: Procedia

Example and Rules of Model Human Processor (MHP)[2]

The Model Human Processor, developed by Card, Moran and Newell, is a design tool that is used for creating an effective user interface. It draws an analogy between the processing and storage facilities in a computer system with the perceptual, cognitive, memory and motor activities of a computer user. The Model Human Processor describes how a user interacts with a computer system:

A visual or audible stimulus is captured.
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The physical attributes of the stimulus are decoded.
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A pop up message appears on the screen (perception).
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The user works out the response that is needed (cognitive processing).
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A motor response is initiated (response).
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The mouse is moved and a button is clicked.

The Model Human Processor provides a set of rules for effective system design:

  • Support recognition rather than recall.
  • Reduce the load on the short term (or working) memory.
  • Support the production of chunks of items to facilitate memory.
  • Frequent activities become automatic and do not require conscious attention.
  • For highly practised responses, requiring a confirmation of the response will not necessarily reduce errors.

Subsystems of Model Human Processor (MHP)[3]

Model Human Processor (MHP) is (1) a set of memories and processors together with (2) a set of principles, the "principles of operation"

There are three interacting subsystems:

  • Perceptual System
  • The Motor System
  • The Cognitive System

Each of these has their own memories and processors

  • the perceptual processor (consists of sensors and associated buffer memories, the most important being a Visual Image Store and an Auditory Image Store to hold the output of the sensory system whilre it is being symbolically coded)
  • the cognitive processor (receives symbolically coded information from the sensory image store in its Working memory and uses previously stored information stired in Long term memory to make decision about how to respond)
  • the motor processor (carries out the specified response)

For some tasks the human being responds like a serial processor (e.g. pressing a key in response to light), for other tasks (like typing, reading, simultaneous translation) integrated, parallel operatopm of the three subsystems is possible, in the manner of three pipe-lined processors; information flows continuously from input to output with a characteristically short time lag showing that all the three processors are working simulataneously.

Memories are described by a few parameters .: storage capacity in items (miu), the decay time of an item (alpha) and the main code type (physical, acoustic, visual, semantic (gamma). The most important parameter of a processor is the cyle time (pie).

The anlayst generates time predictions by analysing a task into the constituent operation executed by the three subsystems and from there calculates how long the task will take and how much processing is involved. This can be doen within three bands of performance: fastman, slowman, and middleman, thus allowing predictions along at least the central and extreme points along the behavioural continuum.

How To Calculate Process Time[4]

The calculations depend on the ability to break down every step of a task into the basic process level. The more detailed the analysis the more accurate the model will be to predict human performance. The method for determining processes can be broken down into the following steps.

  • Write out main steps based on: a working prototype, simulation, step by step walk-through of all steps
  • Clearly identify the specific task and method to accomplish that task
  • For each final step identify sub-levels down to a basic process (in the diagram Fig 3. or chart below)
  • Convert into pseudo code (writing out methods for each step)
  • List all assumptions (will be helpful as multiple iterations are completed)
  • Determine time of each operation (based on the table below (Fig. 4)
  • Determine if operation times should be adjusted (slower for elderly, disability, unfamiliarity, etc.)
  • Sum up execution times
  • Iterate as needed and check with prototyping if possible

SVG version of Human Processor Model
Figure 3. SVG version of Human Processor Model
source: Wikipedia

MHP Process Time Table
Figure 4. MHP Process Time Table
source: Wikipedia

Potential Uses of Model Human Processor (MHP)[5]

Once complete, the calculations can then be used to determine the probability of a user remembering an item that may have been encountered in the process. The following formula can be used to find the probability: P = e-K*t where K is the decay constant for the respective memory in question (working or long term) and t is the amount of time elapsed (with units corresponding to that of K). The probability could then be used to determine whether or not a user would be likely to recall an important piece of information they were presented with while doing an activity.

It is important to deduce beforehand whether the user would be able to repeat the vital information throughout time t, as this has a negative impact on the working memory if they cannot. For example, if a user is reading lines of text and is presented with an important phone number in that text, they may not be able to repeat the number if they have to continue to read. This would cause the user’s working memory’s decay time to be smaller, thus reducing their probability of recall.

See Also

Human Computer Interaction (HCI)
Human-Centered Design (HCD)
Machine-to-Machine (M2M)
Machine Learning
Keystroke-Level Model (KLM)


  1. What is Model Human Processor (MHP)? Toshitaka Higashino, Yudai Asano, Masato Sog
  2. Exampleand Rules of Model Human Processor (MHP)St. Paul Science
  3. Subsystems of Model Human Processor
  4. How To Calculate Process Time in Human Prossessor Model Wikipedia
  5. Potential Uses of Model Human Processor (MHP) Jianta Maya