Thus, while dogs appear to understand humans’ communicative intentions, their concept of human goals appears to be based much more on trial-and-error learning
This piece from the text explains that although dogs can eventually understand human goals, they learn from trial and error meaning they don't fully understand what a human is trying to do but they understand what the human is alright with the dog doing. This information is useful because it could help a scientist further study what dogs might be looking for when interacting with a human in order to learn. This information in the text could be useful to scientists trying to study how dogs use trial and error learning and how the dog can learn to understand what the human wants.