[mod_python] Concurrent requests

I have created a simple .psp script that simply calls sleep(...) and blocks 
execution for a certain amount of time (x seconds).

If I access the .psp script in two instances of my browser at the same time, 
request one waits x seconds, then it finishes, then request two is processed 
and finishes after x * 2 seconds.

Requests are obviously queued and not several Python interpreters spawned to 
handle them concurrently.

Is there any setting that allows you to specify the number of Python 
interpreters that should be used?

Thanks,

-Lars