Scientists spend long hours in the lab and it has effects on their biological behavior even outside the lab. 

Some of these phenotypes may even be permanent. Of course PIs may view these traits specifically in their trainees as positive things.

How do you know when you or a friend has been in the lab too long?

Here is a list of signs (some admittedly stolen from others). 

1) You are at home but start looking for gloves to put on before cooking.
2) You wash your hands before going to the bathroom at home.
3) You are paler than your 99-year old Aunt Sally.
4) You develop pet names for your cells or equipment (e.g. you call your laser or PCR machine "Honey").
5) You wonder if you need to put a biohazard sticker on the trash before you take it out at home.
6) Scientific inaccuracies on TV have made it nearly impossible for you to watch certain shows.
7) When your milk tastes funny, you wonder to yourself if the fridge is no longer at "4 degrees".
8) You sometimes feel just a bit naked without your lab coat.
9) Your desk in the lab has various trinkets from vendors.
10) You wear t-shirts outside the lab that have vendors' names on them.
11) You dream about the lab and it is not a nightmare.
12) You are starting to like the smell of sharpies.
13)  When someone says "Dolly" you think sheep, not Parton.
14) Robust bacterial growth makes you happy.
15) You talk to your cells (or flies, mice, rats, etc.)
16) The security guards/janitors don't even ask for your ID anymore when you've locked yourself out of the lab.
17) The smell of latex means work to you, not play
18) When you hear "PI" it means boss, not investigator to you.
19) when you drop a box of 100 microfuge tubes your are willing to move large freezers and fridges and scour the lab to collect ever single one because the one tube you can't find is the one that'll be essential for that experiment in the future.
20) To you, 'media' is a liquid, not news organizations
21) When you hear the word "tween" you think of detergent, not an age group.
22) When serving food at home you ask normal people if they want an "aliquot".
23) You hate defrosting the freezer,but there's part of you that is curious what tubes and other surprises you might find frozen in the back.