Crab mentality is a phrase popular among Filipinos, and was first coined by writer Ninotchka Rosca, in reference to the phrase
crabs in a bucket. It describes a way of thinking best described by the phrase "if I can't have it, neither can you."
The metaphor refers to a pot of crabs. Individually, the crabs could easily escape from the pot, but instead, they grab at each other in a useless "king of the hill" competition which prevents any from escaping and ensures their collective demise.
The analogy in human behavior is that members of a group/organisation/society will attempt to "pull down" any member who achieves success beyond the others, out of envy, conspiracy or competitive feelings.
As a result of this dynamic, social change can be very hard to achieve. It takes a lot of effort and energy to break free from the ‘keep quiet and don’t rock the boat’ mentality of the crab pot.
We might consciously disagree with many things the group thinks and does, but we feel too uncomfortable to speak up. It is so easy to be pulled back into the familiar crab pot, remaining silent about the issues in the world around us. The pullback is very strong, and the world outside seems too visceral and dangerous to go it alone.
The concept figures prominently in Terry Pratchett's novel "Unseen Academicals." A fishmonger does not bother to keep a lid on the crab bucket because "any that tries to get out gets pulled back." The protagonist comes to realize that her social status results not from external repression, but from her own low expectations of herself: "The worst of it is, the crab that mostly keeps you down is you."
This term is broadly associated with short-sighted, non-constructive thinking rather than a unified, long-term, constructive mentality. It is also often used colloquially in reference to individuals or communities attempting to improve their socio-economic situations, but kept from doing so by others attempting to ride upon their coat-tails or those who simply resent their success.