With incandescent bulbs, the flicker is so low that I would say it is impossible for human to see it. If you shoot a several frames in incandescent lighting with short shutter times (like 1/1000 s), they come up with almost exactly the same exposure. The filament has some heat capacity so it dims only very little in 10 milliseconds. And, the lower the lamp design voltage, the more heat capacity in filament. 12V halogens take literally a second to "shut down" completely!

However, with fluorescent lights, some people (but very few) actually can see some flicker, or not see but rather "sense" it. It is not usual, but some people report tendency to headaches in strong fluorescent light. Which part of the cause is the high level of "strong" light and which part is due to flicker, it's hard to say. I have attached a series of (digital ) pictures of a fluorescent light I shot at 1/1000s to show the flicker.

The frequency of the flicker is 100 Hz or 120 Hz because the light is generated on both half-cycles. As a comparison, the CRT television flicker is either 50 Hz or 60 Hz depending on the system, and film projection in the movies is 48 Hz or 72 Hz depending on the shutter type.