There's also inputs into their environment that influence whether they move via ...

Fomite on Oct 23, 2013 | parent | context | favorite | on: Dr. Arjun Srinivasan: We’ve Reached “The End of An...

There's also inputs into their environment that influence whether they move via random tumbling, or directed movement, allowing them to move toward something.

While they might not desire anything, they do definitely seek out things.