Here’s a more detailed description for those that like to read up: https://rarehistoricalphotos.com/nasa-spiders-drugs-experiment/
Curiously enough when a similar experiment was first performed decades earlier the original intent was to get the spiders to weave their webs during different times of the day, rather than alter the pattern.
And they gave them up to 100 µg, which is a not-too-strong but definitely noticable dose for humans.
Maybe that’s where the micro dosing idea came from.