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ISSUE 14 -Q2 2005

Designing intersection flows
Avoiding problems with forms where users have to choose between alternative ways to proceed

When forms give users the option to continue in two or more alternative directions, such as registering as a new customer or signing in as a returning one, unfortunate users will take the wrong turn if it isn't unmistakably obvious which way they should go. In this article, we'll take a look at a few intersection flows that have caused users problems.

Communicating to users how to fill out a form where each field has to be filled out in a linear manner is relatively simple. Most users even understand when we try to tell them that some fields are optional and some are required. But when we ask users to choose between two or more alternative ways of interacting with forms, things can go wrong if we don't communicate the options in a clear and obvious way.

Intersections flows come in many guises. In the following we'll look at a few that have caused users problems.

New or existing customer?

A classic intersection problem is the one below where users have to sign in or register as a new customer.

Forms have a fatal attraction on users, and both new and returning customers will start entering their e-mail address in the left column. Few will notice the text telling that this is for returning customers only. Some newcomers will start entering the password for their e-mail account and some will think that they are creating a new password specifically for this site. In both cases they will receive an error message telling them that no account was found.

One solution that has proven to work quite well is to combine the sign in and registration into one form using radio buttons. In this interaction design, users are explicitly prompted to make their choice between the two options.

In this new and improved design we actually still have a potential intersection problem, since users can choose to have a new password send by clicking the "Forgot your password" link. Since it's not uncommon that people forget their password, it would make sense to integrate this feature into the sign in form.

To lighten the burden for returning customers we can pre-select the "I have a password" option if the user has signed in before. Also, if the user starts entering a password, the "I have a password" option should be selected automatically.

Search or select one or more categories

An interaction design that I've seen fail big time in usability tests is the one below.

Here the user is asked to choose between one of two search strategies: searching for an item or choosing one or more categories from the check box list.

The problem with this design is that the users won't read the text telling them that they have to choose between the two strategies. Instead, they enter a search term, select a category from the list, and hit either the Search or Next button.

One way to deal with this problem is to change the check box list into a list of links. The users won't be able to select more categories at the time, but in most cases they can do without it as long as they can go back and select another category.

Search site or search Yellow pages?

Another intersection problem that I've seen fail in usability tests is when two search functions are confused with each other. A typical example is an intranet with separate site search and search for employees, where both features are placed prominently on the front page because they are both considered important to the intranet.

Even though it's clearly stated that this is the Yellow pages and you have to enter the name of a person, people will try to use the Yellow pages search for site wide searches. People don't stop to explore the design in detail. If their task is to search the site and they see a search button and an input field they will assume that this will do the job. It's not that people don't understand the distinction - they just don't notice.

To avoid confusion, we could somehow combine the two search functions. One solution would be to turn the site search into a scoped search letting users choose between searching the site and searching the Yellow pages.


Chances are that people won't notice the two options. But if we include search results from the Yellow pages with the site search results, this won't be a problem.

In conclusion

As said, intersection flows come in many guises. In this article, we have looked at a few that I know have caused problems for users.

There is a potential problem if forms are involved and users have to choose between this and that in order to proceed. We should be alert if two or more forms are present on the same page, i.e. if there are two or more sets of input fields with each their submit button - especially if they are placed close to each other and if they work in a similar way.

There seems to be two ways to eliminate intersection problems. If possible, get rid of options which aren't mission critical. If this isn't possible, combine the options into one clear dialogue.

Filling out forms is like drive-by shooting. We cannot expect people to read our instructions - not even bold headings and labels above the input fields. To avoid confusion, our interaction designs should communicate the options that the users have in a very clear and obvious way.

Text: Henrik Olsen

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