Seems plausible that the bees were able to associate the colors with "many" or "few" rather than (N+/-1). Seems like if they were able to make that general ass

Seems plausible that the bees were able to associate the colors with "many" or "few" rather than (N+/-1). Seems like if they were able to make that general association they would do better than chance, but still fail often. Which could explain why the effect is fairly weak. Would be interesting to see if the bees success rate at addition was proportional to the starting value (ex. 1+1 has higher failure rate that 3+1)