It's a visual count. The visual system probably isn't optimized for counting. It identifies and tracks objects, but not many. I'm not surprised 4 is a common bo

It's a visual count. The visual system probably isn't optimized for counting. It identifies and tracks objects, but not many. I'm not surprised 4 is a common boundary, and I also wouldn't be surprised if it were somewhat hard-coded. It could well be limited by a "lower" layer. The experiment is artificial, so it might not represent counting in a more natural setting, where e.g. the objects might have features that distinguish them better. The article brushes over that.