How much evidence does it take to change our beliefs about the world? Sometimes, when we don’t really care about the belief, it doesn’t take much evidence at all. For example, say you like ducks and believe mallards are the most devoted of partners. That’s a good belief- mallard marriages stay together about 91% of the time. They’re more steadfast than American marriages, which along with the Nazca Boobie, split up 40% of the time. And they’re way better than flamingoes, who break up 99% of the time. BUT, your belief about mallards would be wrong because Albatrosses are 100% faithful. They never break up. In this case, unless you really, deeply believe in mallard fidelity, it probably didn’t take much to change your belief.
In other instances our beliefs are much more entrenched and therefore much harder to change. Take, for example, our beliefs about intelligence. You may not even think you have beliefs about intelligence, but just because they aren’t well articulated doesn’t mean they aren’t there. Think of someone you know is smart. How do you know she’s smart? Whatever criteria you thought of form part of your beliefs about intelligence. How about when ants form bridges, is that a sign of intelligence or just a fluke of adaptation? What about this wily honey badger? The author Michael Pollan wrote a great article about the intense debates surrounding plant intelligence.
My point is that our beliefs about intelligence are like a complex net of largely unexpressed assumptions. Evidence may change certain strands of that net, but in order to really change the belief one must look at the overall structure of that net. You do that by asking- What do we really mean by intelligence? That’s why it would take a large amount of evidence AND a philosophical shift to make scientists feel comfortable with a term like “plant intelligence.”