If you gaze at a distant object, each eye sees pretty much the same image. If you look at an object within reach, then each eye sees the object from a different perspective.
Your brain is able to detect these differences and has learned how to judge the distance to a near object.
The mantis study claims to have demonstrated that the insect will basically ignore an object which might otherwise be considered food if the object seems to be at a great distance. However, if the mantis detects that the object is within reach, then it will attempt to catch it.
Thanks.
I do see your comment as saying essentially what I said.
Popular articles on scientific studies are usually poorly done and often the actual basis for the study is not well explained.