Guidelines for inter-word timeouts (aka ep.EndSeconds or incompletetimeout)
Posted by: eolvera, in Usability, Dialog Design
There was recently a very interesting discussion on the VUIDs board regarding timeouts and their guidelines, so I decided to share with you the ones I use for “inter-word timeouts” (also known as ep.EndSeconds in the Nuance platform, or as incompletetimeout in the VXML world).
By inter-word timeouts I’m referring to how much silence takes place “mid-speech” before we assume the caller has stopped talking. This parameter is important because there are certain types of information (and therefore responses) that generate natural pauses. Therefore we need to allow for an appropriate amount of time within the response (e.g. someone saying their telephone number and pausing between the area code and the phone number), while at the same making sure it is not too large since that same timeout will have to expire in order for us to consider the caller is done.
One more thing to keep in mind is that these are not really guidelines but rather baseline recommendations you can use, which then need to be reviewed and adapted based on the context of the application, your audience (age and language play a role here) and the type of prompt. Once these suggestions are implemented and rolled out, they can be optimized based on Usability tests and actual Pilot data.
- Single, short word responses (Yes/No questions included): 0.75 sec
- Short word Menus (e.g. “Checking”): 1.0 sec
- Long word/sentence Menus (e.g. “Get my account balance”): 1.5 sec
- Number/Amount capture (e.g. check amounts, rates, etc.): 1.0 sec
- NOTE: You may want to go up to 1.5 sec for really long amounts such as a mortgage loan
- String sequences (e.g. account numbers): 2.0 sec
- NOTE: Depending on the number length and its natural pauses, you can tweak this number. For example, use 1.5 sec for 4-digit PINs, 2.0 sec for 9-10 digit numbers such as a phone or fax, and even 2.5 sec for long numbers such as a 16-digit credit card number.
Finally, regarding age, I’ve found out that you tend to need longer pauses for higher age ranges, specially if it’s information they need to read back (e.g. from a statement) or write down (e.g. a confirmation number).
Language wise, some languages are more synthetic than others (e.g. English is very synthetic), so I’ve found that in more explicit languages (such as Spanish and French) your grammars need to be more robust which in return may require longer pauses.
Any others I might have missed?