The FAQ explains that you can get paid $75 for it.
Do I get paid?
Yes – it depends on the type of study, but typically we pay $75 for each hour that you spend with a Google researcher, either in person or on the phone. Most studies last for one to one-and-a-half hours. We don't pay for your travel time, or travel expenses, though. For online surveys, which you complete from your own computer, the amount varies, depending on the length of the survey.
The FAQ is pretty funny, it also explains that you do not have to attach electrodes to your body for this study. But you do need to be 18 years or older.
When I first reported this, I named it, Want To Be a Google Lab Rat? but I did not see it may be worth $75.
Forum discussion at DigitalPoint Forums.