Intense experiences are well understood to be dramatic events. We all know that some people pursue activities which substantially increase or decrease their level of emotion. Exhilarating hobbies are commonly associated with thrill seekers, yet not so often are those who attend horror movies or opera placed in the same group. All of the above activities share the common thread of elevating the emotions of those involved to a point where their focus is entirely captivated with their current perceptions. A myriad of interests are sustained by countless, varied enthusiast endeavours.
Such pursuits are a division of a wider evolutionary process. We are innately governed by the extremes of our perceptions. Hope motivates us towards manifesting the things we most deeply want to come true while terror indicates something which could destroy those things we hold so dear. Two extremely intense emotions are at the heart of our orienteering of life.
At a most basic resolution, negative emotions are associated with things to avoid while positive emotions with nourishment and success. Intensity is what makes a prism of this spectrum of emotions. All of the emotions are governed by and expressed as different intensities – an evolutionary principle which runs through all the emotions. The same evolutionary bundle of reactions is expressed at different intensities, so to suit a suite of escalating environmental circumstances. At each different level of intensity, the same bundle of reactions is quantified as a different emotion – such as being scared, fearful and terrified.
Our interface between the world and our reactions to it (emotions) is perceptions.
If mild danger is perceived, we feel scared.
If significant danger is perceived, we feel fear.
If extreme danger is perceived, we feel terror.
Each level of danger perceived causes the body to adapt its metabolism, its psychological processes (e.g. vigilance), and its posture to an appropriate extent so as to be adequately prepared to deal with the “perceived” threat.
In so showing that each emotion is a specific motivation with an accompanying set of evolved biological dispositions, tied to intensity, which complement the emotion’s adaptive aims.

The backdrop is thus set for us, as humans, to behave according to our perceived environment. Weapon focus is a term used to describe one such adaptive “psychological” process that’s bundled with terror and elicited from the most intense object within a terrifying scene.

As the page on terror states, “weapon focus forcefully redirects attention in milliseconds onto the source of the threat whilst excluding other information from being processed. People’s subsequent memories are then overwhelmingly biassed towards intensely threatening objects.
A clear demonstration of this weapon focus was provided by an experimental study that showed participants a videotape of a staged bank robbery. For half of the participants, towards the end of the violent crime, the escaping robbers shoot a small boy in the face. The other half of the participants watch the same robbery with only one difference – there was no shooting of a boy. Those who watched the gunshot showed impaired memory of events immediately preceding the graphic violence, yet their memory preserved vivid recall of the shot itself. Eye-tracking instinctively follows the intensity of perceived events. The more extreme a perception, the less consistent memory becomes around it – preceding and succeeding the apex of intensity.”

So here we have a psychological phenomenon that “violently” redirects attention to focus upon a weapon and then constricts the brain’s resources to attend processing the interactions of the weapon in high definition at the cost of reducing the rendering of surrounding material to near zero. All of this is beyond conscious control and enacted in milliseconds.
Leaving, in its wake, a high resolution memory of the path a weapon took and its effect on the environment.
A violent memory purposefully etched with vividness into memory by the subconscious itself. A memory so disturbing, yet in many cases constantly and compulsively accessed again and again. Relived repeatedly, on an ongoing basis, to the point where it can feel as if it’s burning a hole in one’s mind. As if, a video of the event is being screened in a subconscious theatre. Free from conscious will, yet taking up considerable attention, and making it difficult to focus on anything else fully.

Surely, the evolutionary function of this weapon focus is to first demand attention is paid only to the source of an intense threat, so in a real life situation where a weapon is encountered (say a gun or knife), it can be tracked and avoided or tackled. After the threat to life has passed, every detail of the vivid memory is forensically investigated by the subconscious to produce a thoroughly updated narrative with which the owner uses as the basis for adaptive behaviour. Therefore the process aids dealing with the imminent threat to life and then recognition of similar events in the future.
All of which seems to be deemed so important that we’ve evolved a subconscious routine (instinct) to initiate and complete the process without any conscious intention being needed.
What other logically explanation is there?

A similar process is probably at work in other emotions which have wonder as part of their core purpose – such as admiration, amazement, anxiety, and shock.

The intensity outweighs probability function is a major mechanism involved in weapon focus.

Weapon Focus