There is a concept, “the uncanny valley,” that describes the human ability to unconsciously recognize things that are, well, just wrong. For example, how a CGI object moves, or even if a robot or computer is human, making it a bit of an overlap with the Turing test in concept.
These concepts have been around for a while and speak to the human level of comfort with the real over the artificial, and the consistent over the mixed. Recently, I recognized a reverse of that when it comes to plot construction thanks to the increased approach of using improv in the midst of scripts rather than fully scripted or fully improvised movies. A great example of this is Adult Beginners, where some nicely crafted script is interspersed with improvised scenes. Those moments, while well played and nicely edited into the film, sit oddly. In other words, the fully real interchanges appear unreal, while the crafted, more artificial bits, if you will, feel more natural. I don’t think this is just a matter of the quality of the improv, but more about the juxtaposition of the two which rub against each other in the wrong way. However, I do think there is a preferred leaning to the crafted script over improv for viewers.
Film has gone through many movements over the century-plus it has been around. We have been trained to expect fully crafted moments. This has been true for millennia with stage plays as well. This is a plus and a minus. We have expectations based on structure. Those structures are often unconsciously recognized by most of the audience, but are very obvious to those aware of the tropes and standards. Those expectations help us pick up clues and allow for great catharsis when love conquers, evil falls, or the little guy wins. But if you consciously know it is coming from the outset of the story, the result can sometimes be very unmoving. Scenes of improv have been used to help shake up those expectations, break the rhythms; make you sit up and take notice and think of the story as unpredictable as life really is. But it tends not to work as they stand out as, well, wrong.
This is why I tend to watch a lot of foreign fare; it riffs on the plots I grew up with rather than delivering them as expected. I typically recognize plots in seconds when watching something from the States. Both domestic and foreign approaches are similar, but I get moments of surprise by viewing the foreign because they are based on slightly different cultural templates. Templates, to be fair, which are highly familiar to their local audiences, just foreign (literally) to me.
There are uses of improv that do work, but they are, typically, used as the whole of the film and are then highly edited (aka crafted) into a cohesive whole. Robin Williams turn in Aladdin comes immediately to mind, but there are many out there. In these cases the improv was either an exploration to find opportunity in a story, or a way to provide a uniqueness and deep well of raw material from which the director could shape the story for audiences. Once crafted, it is no longer pure improv, it is scripted, just not in the traditional sense. And by being given shapes we recognize as part of the story-teller’s toolbox, we find it real and comfortable, though it is utterly artificial. Watch for these reactions in yourself as you view movies… what parts feel right and real versus artificial or out of place. This isn’t about bad directing or acting or script, it is about finding those pieces that don’t fit by their very nature, not because the craft was weak… it provides an interesting lens on the post-modernist films and experimentations with social media conventions that are starting to flood the market.
For further reading: A wonderful little retrospective of 2015 movies around the uncanny valley over at Fandor many of which are discussed on this site. There are also some nice examples of the idea over at Stranger Dimensions as well. (And for some truly silly, completely off-topic analytic fun, check out Wired’s Force Awakens vs. A New Hope statistical comparison if you haven’t found it yet.)