How to tacle with common usability violations of VUI

How to tacle with common usability violations of VUI UX Camp Europe - Berlin , June 2011 Pavel Růžička (T-Mobile Czech Republic)

#1: Menu length
Menu length determines how long you have to wait in order to hear all options explained with a prerecorded system message
Most callers who encounter long menus hang up in frustration, make mistakes in their choices, or try to connect to an operator
What to do?
Keep the greeting and preamble short (under five seconds) and present choices quickly.
Consider human short term memory (30 seconds)
Include only necessary legal disclaimers
Eliminate Marketing Messages

#2: Number of menu choices
In DMTF applications the caller must remember both the subject and the digit to select
As soon as the caller assumes that the current option within a list is the right option to choose, he/she will choose it (even if it‘s wrong)
What to do?
Four menu items are optimal
Arrange choices by popularity
Announce availability of details and allow users to choose it
Consider using verbs instead of nouns for menu items
"Administrate" instead of "Administration" "Check billing" instead of "Bill"

#3: Operator access
There is always battle between users who like talking to a real person and IVR‘s that have the goal to exactly avoid that
What to do?
Callers should know that they always have the option of speaking with a live agent : This will reduce frustration and increase user confidence
Don‘t try to hide access or make it conditional
Make it less attractive, e.g. by informing about longer waiting times
Think about rewarding users who try automation
Automate what’s useful – not what’s possible

#4: Speech Intelligibility
The understandability of the prompts, menus and instructions is crucial
Quite often there is a wrong use of prosody
Prosody is a part of speech not associated with content, but with style of delivery
What to do?
Use friendly, plain pronunciation
Educate your voice talent to use appropriate voice modulation
Provide script details for the voice talent
Keep prompts short, but not fast
verbs instead of nouns are better for the most languages/cultures

#5: Speech pacing
Speech Pacing is the rhythm and speed of the recorded words callers hear
Non-professional speech talent tend to rush through scripts when they are recording prompts
Some designers think that the faster you speak, the faster you are serving the caller
What to do?
Generally, slow down the speed
Use appropriate pauses between words and sentences
Be aware that callers are not specialists

#6: Forced output
Forced output can‘t be interrupted by the user
This can be especially trouble for power users who know exactly what their preferred task sequence is
Many forced messages are the legal disclaimers and marketing messages
What to do?
Generally enable Barge-In
Inform the caller about possibility to interrupt
If you have to use forced messages, keep them short
Try to find way how to indicate to the user that barge-in event has been detected - even current media-platforms don 't support it
immediatelly play an earcon or something like "aha"

#7: Task completion
A tasks is a sequence of input steps to fulfill a request
The entire task is only as good as the worst input step
What to do?
Make use of navigational options – step back, cancel...
Analyze what step is the worst step – then improve it
Compare length of task using implicit vs. explicit confirmation steps
Use variations in wording during reprompting – dialog will also sound more natural

#8: Error recovery
Error recovery techniques are used to guide callers out of a known “bad state” and back into a “stable state”.
Errors can be caused by users (misunderstanding) or by systems (backend or misrecognition)
What to do?
Use silence or "earcon" as an indication for turn taking
You can provide "try again" option
Provide graceful degradation
Build touch-tone fallback into speech applications
Base d esign on the reality of errors - test driven development (TDD)
Don’t declare errors, ask to clarify input

#9: Predictability
Unpredictable behavior includes customer delay time and unexplained hang-ups or disconnections
Customer delay time is the total amount of time a caller is waiting to complete a task when nothing of value is happening
What to do?
Once you think everything is okay, you are in trouble
Track IT infrastructure downtime
Track call center anomalies and traffic
All of the backend systems must not shorter timeout than his underlying provider in hierarchy of components – or timeout event must be indicated
Consider asynchronous call of backend

#10: Dead ends, unattended hang-ups
Dead end are conditions that forces the caller to hang up and call back
Usability test subjects indicate a strong dislike of having to make repeated calls to get service
What to do?
Test every path on a regular base
Audit the system periodically and test all numbers/words at every level of every menu
Build in caller-in-control features like go back , main menu and agent into your application .

Summary: C ommon usability violations of VUI
#1: Menu length
#2: Number of menu choices
#3: Operator access
#4: Speech Intelligibility
#5: Speech pacing
#6: Forced output
#7: Task completion
#8: Error recovery
#9: Predictability
#10: Endless loops

Resources
Udo Glaeser , DTAG (presentation): VUI Best Practices - Athens, May 2011
Larson-Tech: Ten Guidelines for Designing a Successful Voice User Interface
Voxeo : Interact Naturally With Your Callers

Pavel Růžička Programmer – Analyst Service Development Department T-Mobile Czech Republic a.s. Tomíčkova 2144/1, CZ 14900, Prague Phone: +420 603 416974 E-Mail: [email_address] Web: http://pavel-ruzicka.net/

How to tacle with common usability violations of VUI

by Pavel Růžička on Jun 15, 2011

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