CIS465: Adv. Info. Sys.Memory Systems

Min Song

Information Systems Dept.

The Human Information Processing System

To support human systems, need to know something about its basic characteristics memory performance characteristics behavior of input and output channels internal architecture

The Human Information Processing System

As with computer, one basic activity is info processing.

HC Interface is for exchanging information So, focus on user as info processing system, and

study how the user handles info input and output.

Basic Information Processing Units

Memories

Computer

Human

Registers Short-Term Memory Main Memory Intermediate Memory Disks Long-Term Memory Tape, cards, optical disks Books, pictures,

External Memory Input Devices Keyboard, Mouse,

Touchscreen Touch

Voice Recognizer Ears Digital Scanner Eyes Output Devices

Screen, Printer Eyes Voice Synthesizer Voicebox The Glove Hands Processes Operating System Executive Control

Unit Compiler Pattern Recognition Applications Knowledge and

Skills

Human Constraints and Task Accomplishment

Limited available resources. High use, reduced processing Resource-limited Tasks Data-limited Tasks

Reduce Memory Load

Reduce demands on user's short-term memory Establish meaningful defaults Define intuitive short-cuts Visual layout of user interface should be based on a

familiar real world metaphor Disclose information in a progressive fashion

Competition for Critical Resources

Multiple tasks interfere and compete with each other. Two basic tasks in any form of user interaction:

Functional: user works with the content of the problem at hand (e.g., laying out a financial plan on a spreadsheet)

Operational: user works with the tools provided to do the task (e.g., moving the cursor around the spreadsheet or invoking spreadsheet commands).

Competition for Critical Resources

Functional and operational aspects compete for same scarce resources.

Skill in task performance can free up cognitive resources overlearning, “chunking”

Basic Processes of Human and Computer Systems Computers work in cycles:

read input data, convert to internal form (read-scan phase)

interpret the data (think phase), provide an output response to the input (response

phase). Humans process data in a similar cycle:

read and/or scan the input data presented to them (read-scan)

interpret this data by thinking about it (think phase) prepare appropriate response by sending signals to the

motor system (e.g., speech) (response).

Basic Processes of Human and Computer Systems

Three basic human systems handle input and output for the cycle: 1. the perceptual system (read-scan) 2. the cognitive system (think) 3. the motor system (respond)

The Perceptual System

The basic perceptual systems are: auditory visual touch

Each has a buffer, preprocessing and connection to cognitive system

The Cognitive System

holds new information short term memory (STM) [aka WM]

tries to match it to elements in long term memory (LTM)

If the information is completely new, relatively few matches are found user has to rehearse info in STM to keep it from

decaying might store it in LTM

The Cognitive System

Example of rehearsal: remembering a phone number

Short Term Memory

small capacity, fast read/write speeds, highly volatile Tasks which can cause forgetting in STM include

those with distractions (e.g., multiple attention grabbing items

happening at the same time). low discrimination between presented information “large” number of unique (unrelated) items

Long Term Memory

unlimited capacity, slow read/write speeds (about 5 seconds per item stored), fairly stable

forgetting=losing links, not nodes recall tends to be more general than specific declarative: facts procedural: rules, how to do things

The Motor System

comprised of many different muscle systems controlled primarily by the visual system Motor movements viewed by the visual system, which

sends its information on to the cognitive system, which then makes minor adjustments in the motor movements. These are sent as commands to the muscles to adjust the movement.