LED strip lighting even without a positive terminal

[Adhith]

hello everyone..
I have been making a project with some 12V RGB LED strips. while trying to check the LED strips I found something interesting. I just connected the ground terminal from a 12V wall adapter to the terminal "B" and left the positive terminal disconnected to the strips but, while touching the positive terminal on the strips  with my finger I saw that the led strips are lighting up with a very low brightness. This also happens even when i tough anywhere in the strip with my finger. I wonder how this is happening. anyone could explain to me about it. I'm attaching a pic of the test that I have done.