Since 2012, neuropathologist Daniel Perl has advocated for this theory: specifically that blast waves caused physical damage at the intersection of the brain's gray matter and white matter , where microscopic analysis of the brains of former soldiers who suffered from PTSD reveals a "brown dust" of scarring, in regions that are neuroanatomically associated with sleep and cognition.

Perl and his team examined brains of service members who died well after their blast exposure, including a highly decorated Special Operations Forces soldier who committed suicide. All of them had the same pattern of scarring in the same places, which appeared to correspond to the brain's centers for sleep, cognition and other classic brain-injury trouble spots.

Ibolja Cernak is a Bosnian scientist who conducted a study on 1,300 veterans of the Bosnian/Serbian conflict, which confirmed much of Perl's hypothesis. Adherents of this hypothesis believe that the action of a blast weakens the material connections at their intersections -- perhaps by compressing the body and forcing blood into the brain, putting a "shearing load on brain tissues."

In a new paper uploaded to the ArXiv pre-print server, researchers at the Max Planck Institute in Saarbri1/4cken, Germany demonstrate a method of identifying individuals even when most of their photos are un-tagged or obscured. The researchers' system, which they call the "Faceless Recognition System," trains a neural network on a set of photos containing both obscured and visible faces, then uses that knowledge to predict the identity of obscured faces by looking for similarities in the area around a person's head and body.

The accuracy of the system varies depending on how many visible faces are available in the photo set. Even when there are only 1.25 instances of the individual's fully-visible face, the system can identify an obscured faced with 69.6 percent accuracy; if there are 10 instances of an individual's visible face, it increases to as high as 91.5 percent.

In other words, even if you made sure to obscure your face in most of your Instagram photos, the system would have a decent chance identifying you as long as there are one or two where your face is fully visible.