Individual intentionality in the way I am talking about it here is basically "I have a problem, how do I solve it?" If you add a theory of mind, you can get "You have a problem, how do you solve it?" Shared intentionality takes it one step further and adds "We have a problem, how do we work together to solve it?"
According to
Michael Tomasello, chimpanzees don't have shared intentionality. You would never see two chimpanzees work together - like carrying a log to reach a bunch of bananas - they just can't think that way. According to
Jonathan Haidt, one of my favorite psychologists, the important rubicon humans crossed on the way of becoming an ultra-social species (able to work together by the millions,
without being related*) was inventing shared intentionality.
Tomasello did a series of experiments on toddlers and chimpanzees. One series of tasks were motoric tasks, and chimps and toddlers were about equally good at doing this. Chimps are really smart, so you can give them fairly complex tasks and they will solve them. The second series of tasks were tasks that required social interaction - picking one of two cups with the only clue being that the human is looking at it, or pointing at it. As someone who has had cats and dogs know that that's a large difference between them - if you point, a dog looks where you point, a cat looks at you**.
So how do I build a species without shared intentionality? The "mind-blind" disadvantages are "Clueless", "Low Empathy" and "Oblivious", but this is not quite something like that. Chimps can understand the reason behind another chimp's actions, it's just that they can't cooperate. Any ideas?
* we are the only species that can do that
** this may not be true of all dogs and all cats or even all chimps, so please don't point out the exceptions. An intriguing possibility is that cats are evolving shared intentionality, but there's a reason there are so many "trained dog" movies and so few "trained cat" movies