To Err is HumanComputational Limits to Human Thinking :

Implications for the Design of Human Centered Interfaces

Raj ReddyCarnegie Mellon University

Pittsburgh, PA 15213March 16, 2000

www.rr.cs.cmu.edu

Human Strengths and Human Limitations

Strengths: People communicate using speech and natural language tolerate errorful, ambiguous and imprecise input exploit vast amounts of knowledge learn from the environment

Limitations: People make errors tend to forget become impatient get confused need to collaborate tend to be lazy

WIMPy Interfaces have largely Ignored Human Strengths and Human Limitations

Need to move towards SILKy Interfaces: Speech, Image, Language and Knowledge based human centered interfaces

Video of Carnegie Mellon Communicator illustrating interactive spoken language dialog

To Err is Human

• Problem: – Catastrophic loss of data: “I didn’t mean to do that ”– Unanticipated side-effects: “how did that happen??”

• Causes:– Sensory, Cognitive and Motor overload– Information Overload: “Like being in a traffic jam”– Timing Errors: Simplify the task

• Present Solutions:– Partial Undo– Dialog Boxes

To Err is Human (Cont.)

• Future Opportunities:• Unlimited Undo

• Anytime Anywhere Abort

• DWIM (Do What I Mean)

• System Issues:• Require redesign at the OS level, network level

and the application level

To Forget is Human

• Problem:– A non-expert occasional user can’t be expected

to remember the details

• Causes: – Forgetting is the loss of indexing structure– Redundancy in the indexing structure is the key

• Present Solutions:– Recognition vs. recall: GUIs and Menus– On-line manuals

To Forget is Human (Cont.)

• Future Opportunities:• Use of color, fonts, voice responses for focusing

attention

• Intelligent Help • “How do I” and “What if” MultiMedia documentation

• Learning by Doing and Learning by Example

• “Reference librarian” agent

• Chemical abstracts metaphor

• System Issues:• On-line help must change: enormous investment

To be Impatient is Human

• Problem: – Time to get the answer in interactive problem

solving• Reduce the response time

• Network operations: Unpredictable retrieval and browsing times

• Automatic MSN and AOL updates at login

• Present Solutions:– Hour glasses and wheels

• No idea how long it will take

– Progress bars

To be Impatient is Human (Cont.)

• Future Opportunities:• Updates in the background

• Learn from experience: self-aware systems

• Look ahead retrieval and computation

• Hurry-up algorithms

• Keystroke model

• Systems issues:• Introduction of monitors in OS and applications

• Background multitasking: intermixed packets

To be Confused is Human

• Problem: – Unable to deal with information clutter

• Causes:– Information overload– Computational constraints on human thinking– Incomplete and ambiguous information

• Present Solutions:– Hide and/or re-arrange windows– Illegal syntax– Restrict use of Natural Language

To be Confused is Human (Cont.)

• Future Opportunities:• Infoglut: Filters and Agents

• Human Attention: Use multiple sensory modalities

• Incomplete and Ambiguous Information: clarification dialog

• System Issues:• Agent architecture and integration into Operating

Systems.

To Collaborate is Human• Problem:

– Many tasks which cannot be done by a single person• Causes:

– A single person may not have the skills to solve a given problem

– Independent / Loosely Coupled / Closely Coupled Interactions

• Present Solutions:– Instant Messaging and Chat Rooms– Serial sequential problem solving– Groupware

To Collaborate is Human (Cont.)• Future Opportunities:

• Concurrent Engineering• Parallel Asynchronous Problem Solving

• Common Language and Conventions• Building a bridge or plane

• Distributed in Space• Distributed in Time and Space

• Systems Issues:• Systems need new representations and architectures

• Collaborative Writing: Transaction Files

• Collaborative Design: Structured Dialog Trees

• Collaborative Planning: Abstraction of Interactive Dialogs

To be Lazy is Human

• Problem:– Most people use a minimal subset of functionality in

Word, PowerPoint, etc.– Most people avoid tasks requiring too much cognitive

effort• PGP - too much work

• FTP - too complex

• Causes:– Principle of least effort

• Present Solutions:– Tip of the Day in Word

To be Lazy is Human (Cont.)• Future opportunities:

• Advice giving agents that look over your shoulder• Just-in-time learning• Gentle slope systems• Agents (wizards!) that know about PGP, FTP, or

whatever• Systems issues:

• Applications that know about their own functionality• End user agent creation technology• Intelligent tutoring tools