(Cambridge University Press), that contains some fascinating insights for software designers.
For example, Nass and Reeves tested how users respond to educational software that speaks with male or female voices. They discovered that people consider "male" computers to be better teachers of technical subjects, but prefer "female" computers for more personal subjects. Should software developers adhere to these stereotypes or rebel against them? Nass dodges that question: "We're scientists, not politicians."
However, he does offer more concrete advice on other subjects. Above all, Nass emphasizes that computers don't have to be artificially intelligent or even particularly sophisticated for people to react to them as if they were real people. In one experiment, Nass and Reeves used a simple text-based terminal to see how people responded to commands worded in dominant or passive language. Result: Users with dominant personalities disliked passive computers, and users with p
assive personalities disliked dominant computers.
"The minute you put words on the screen, you've got a social interface," Nass says. "If it's got contingent behavior, if it fills a social role, and if it uses language, people will perceive it as a person."
After studying the physiological and psychological responses of
computer users, Stanford University's Clifford Nass says savvy
user-interface designers should keep these key issues in mind:
1. Error messages should have a consistent tone and style.
Many programs are inconsistent because different programmers wrote
the error messages, often as an afterthought. Whether the tone is
dominant, passive, friendly, or businesslike can vary according to
the type of application, but it must be consistent. "Although
different people like different personalities, nobody likes a
confused personality," Nass says.
2. Users should be able to customize th
eir software,
but it's
better to offer them a few preconfigured choices instead of forcing
them to set a zillion separate options. "If I asked you to describe
your ideal best friend, you'd probably have trouble," explains Nass.
"But if I showed you 10 people and asked you to choose the one you
like best, you'd find it much easier."
3. Avoid the overuse of modal alerts
(messages that float atop
all other windows and must be dealt with immediately). "A modal alert
is like yelling 'Fire!'"
4. Context-sensitive help is much better than large,
generic
help files that give too much nonspecific information. If someone
asked you for a phone number, would you recite the phone book?
5. Toolbars are frustrating because users must remember
what
all the obscure little icons mean. "They violate the principles of
understandability and comprehension," says Nass. Toolbars are
acceptable if the user creates the shortcut button. The toolbar
should
remain hidden by default until the user is ready for it.
6. Practice random kindness and senseless acts of beauty.
In
one of their most interesting experiments, Nass and colleague Byron
Reeves discovered that users exhibit a measurable physiological
response to random praise, even if the praise is undeserved, and even
though people deny that praise from a computer matters to them. Does
this mean software developers should counterbalance their error
messages with occasional "praise messages"? It sounds crazy, but Nass
and Reeves actually designed a spelling checker that not only flags
spelling errors but also randomly praises the user for spelling
difficult words correctly. The program generates positive responses
that can be measured on brain scanners.
How Computers Press YOUR Buttons
