The inmates read the pedestrians’ nonverbal signals and used those to make their choices. Basic movements such as the length of their stride, how they moved their feet, the way they shifted their body weight, and whether their arms swung while walking, came into play and were interpreted for signs of vulnerability.
These days, we're distracted in our phones, heads down listening on earphones, unaware of who is around you and you don't see their approach. The selection process is most likely even quicker.
Their TWO BIGGEST FEARS are getting hurt and getting caught. This knowledge empowers you in case you are picked. Fight back and cause a scene. The predator wants to commit the perfect crime and, in those few seconds, he assesses whether he runs an increased risk of getting hurt or caught by choosing you.