It did get me to thinking about doing a similar exercise with games, although I have neither the time, resources nor the expertise to do a review of that scope. Again, as with most media, games have a real problem of labelling individuals as psychopathic when they actually aren't and so a great many members of our subject pool would be automatically disqualified. Even then there should be enough to make a survey, although I imagine that they would come mainly from the less-narratively heavy end of the spectrum than most people would expect.
Psychopathy is a funny old disorder in that it is beloved of melodrama and yet the more lurid the invocation the less likely it is to be accurate. Writers like the concept as an explanation for evil acts and yet by definition it has no moralistic explanatory power. In some ways it's fine if you want a villain to commit random violent acts to establish them as a psychopath (although it isn't really) as in many ways the term psychopath is one we use to get an intellectual handle on people who commit random violent acts (although this has been expanded). The problem arises when that label becomes established as a synonym for a certain kind of villain and then writers seeking greater sophistication but lacking the psychological awareness attempt to get into the mind of the character. I am absolutely all for better-rounded villains, but essentially as you provide (emotional) motivation you degrade the integrity of your original diagnosis: as one of the key aspects of psychopathy is invulnerability you cannot retain the right to call your villain a psychopath even as you make them vulnerable.
I'm talking a lot about villains here, but I'm doing so because Leistedt and Linkowski do so too. It is almost a given in their paper that it is always the villains who display psychopathic behaviour. Partly I think this is to do with the general sense in which psychopathy has become a moralistic concept; its essential amorality being consistently read as immorality, and partly it is as they say that psychopathy lends villains danger and intrigue. I also think it is a function of genre expectations, in that when for instance an action film protagonist acts in ways that might in other contexts be considered as psychopathic we don't consider it to be so because they are acting in-genre and we recognise that and so parse their behaviour accordingly. In many of his films James Bond is almost certainly a psychopath, for example, and although this is sometimes made explicit and sometime lampshaded it is usually excused in a way that the psychopathy of the villains he meets is not. Meanwhile numerous films and heroes are based on the Bond model without even that complexity and with the assumption instead that their heroes are just acting heroically.
What does this mean for video games though? It would be easy to shrug and to say that a great many video game protagonists are psychopathic and that by extension they engage players in episodes of psychopathy; and a great many people do say this. It’s all there: the violence, the lack of empathy, the erratic and impulsive behaviour and the emotional invulnerability; I never once saw Mario shed a tear over the first goomba let alone the thousandth. These particular extracts from Liestedt and Linkowski particularly struck a cord with me, especially if you consider the perfect no-deaths playthrough of any particular game to be the canonical version of the events depicted.
"In these slasher films, psychopathic characters are generally unrealistic, accumulating many traits and characteristics, such as sadism, intelligence, and the ability to predict the plan that the future victims will use to escape."
"Psychopaths in films generally possess a number of standard characteristics that are not necessarily as common among real-life psychopaths, ... The traditional “Hollywood psychopath,” generally found before 2000, is likely to exhibit some or all of the following traits ... (ii) a somewhat vain, stylish, almost “cat-like” demeanor; ... (iv) a calm, calculating and always-in-control attitude; and (v) unrealistic, exceptional skill at killing people, especially with blades or household objects (sometimes overpowering multiple assailants with superior armament). These traits, especially in combination, are generally not present in real psychopaths."
So yes, we could say that video games make us inhabit the lives and minds of psychopaths and blunt our capacity to feel in the process but I think that that would be both grossly unfair, to players, game characters and psychopaths alike. the key sentence in those extracts is the last. As I mentioned a few paragraphs ago this is more a question of genre; these characters are not psychopaths within the rules of the world that they live in. To say 'why aren't video game characters more like real humans?' is to miss the point that they fundamentally aren't real humans but are artistic representations of humans instead. The reason I don't feel it as jarringly out of character for Lara Croft to kill hundreds of grunts but feel sad about her dead mate is the same reason I don't feel it is jarringly out of character for Arnie to kill hundreds of grunts in Commando but feel sad about his dead mate. The art, unless you're in a movement like Dogme 95 where verisimilitude is paramount, is in negotiating between abstractions and representations to create something that feels true rather than merely is true. And sometimes that involves building a jigsaw puzzle of different registers and genre tropes to create a bigger and more vibrant picture that maybe has to gloss over some of the details.
The other problem I have with that analysis is that it is particularly teenage in it’s level of insight, especially as it usually comes alongside an assumption that most players are passive consumers in this situation allowing their minds to be dangerously warped by desensitising media. I say teenage because it's sort of this idea that you are the only one who can see the truth and who was affected a certain way by a certain piece of work. It ignores the internal life of others who may not have the inclination or the vocabulary to express themselves, assuming that if feelings or responses are not being talked about then they must not exist.
Video games are getting technically more competent and so are looking at broadening the emotional register of their characters in-game, but to assume that that is happening in parallel with a broadening of emotional register in players is demonstrably false because human emotional evolution is not tied to graphical processing capabilities; I was having emotional responses to games, and questioning the thoughtlessly violent nature of their protagonists, 20 years ago and I am no-one special. I don't mean to say that there aren't plenty of people wilfully missing the point or interacting with a given work purely on the surface level at any given time, myself included. But, my default position is to assume that the way any given person feels about a work of art is much more complicated than the way that they talk about it.
Psychology and in particular anthropology have historically suffered from a version of this fallacy which has left a legacy of popular belief in the emotional simplicity of both sub-cultures within and external cultures to the western education system from which they draw their explanatory framework. Which actually, neatly, brings us full circle to the initial problem with labelling people psychopaths: which is that it can easily fall prey to the same instinct to ignore internal lives and pathologise solely on the basis of external actions. Which is not to say that the concept of the psychopath is without use or validity, but that it's usage in media is certainly fraught with problems.
Liestedt and Linkowski (2013) Psychopathy and the Cinema: Fact or Fiction? Link