The JWs are not alone in being affected by cognitive dissonance. I think the persistence of the Israelite religion itself as well as the birth of Christianity can be greatly explained by it.
When Jerusalem was destroyed the Israelites didn't admit they were wrong about YHWH, but believed in him more devotedly, coming up with explanations for why he had them destroyed. Monotheism was born.
The disciples who believed Jesus as their messiah, couldn't face up to the prospect that they were wrong when he was suddenly executed as a criminal. They created an entirely new religion in order to maintain their sense of correctness, rather than admit they had made a colossal mistake. Christianity was born.
When Jesus didn't come in 1844, many Millerites didn't abandon their belief but created a scenario where they were correct after all. Jesus had come, but invisibly, and those that believed that, believed all the harder. The Seventh Day Adventist's were born.
Then you have Russell. People on bridges in white outfits ready to be taken up into heaven. Did Russell or those that came later admit they were wrong about Jesus coming in 1914? No,those that stayed, used the very same explanation as the Seventh Day Adventists.
The ones who stay despite all contrary evidence are the most psychologically invested. They would be the most damaged by having to acknowledge they were wrong. They will have been in the longest, given up the most, their sense of identity and self worth fundamentally linked to their belief system. When that belief system is threatened, their brain will distort reality in order that they remain right. Because admitting you are wrong about something fundamental is psychologically painful - traumatic even, and the brain will protect itself.
In this way, I think, Judaism, Christianity and the JW's can all thank cognitive dissonance for their continuing survival.
