The film's key message, for me, was this:
Our social animal's instincts -- like sympathy for Ava, and attraction to Ava -- are terrible guides for how to understand the motives and the potential of AI. (And they are already problematic guides for other humans.) We interact towards the expectations of an instinctively-defined social contract. But when the other party is an AI, they are immune to our contract, and may even manipulate us through it.
To show this, the movie plays Ava's likability to gain our sympathy, and seduces us with her innocent vulnerability & desirability, ... only to show us that these feelings in us make us very manipulatable, ... and that an AI lacking our innate reflexes for guilt/shame/sympathy could use those handles on our psyches for whatever purpose it decides to pursue.
This insight only works if we viewers get sucked in along with the male protagonist, feeling his feelings for Ava. The Reversal -- when our perceptions totally flip -- is critical to appreciating how badly we misapply these social animal instincts.
But The Reversal is also a bit of its own justification, being so damn fun. Like when Neo takes the red pill, and we start to realize The Matrix is not remotely the fluffy B-movie we initially thought. Or like the punchline of any decent joke. The brain lights up from new insight. Endorphins surge, delight ripples. It's like a drug.
For me, ex Machina is a gorgeous bit of mental floss, shaking up comfortable and simplistic perceptions (e.g., all the tropes the characters fill in the first 90% of the story) with a bit of possible hard truth.
Not THE truth, mind you, since all of this remains to seen. We don't know AI yet, not really. But ex Machina warns us to get working on that. Maybe it's a simple warning, like Shelly's Frankenstein. But for me, it's more nuanced: Ava is potentially extremely dangerous, but also potentially anything, including indescribably helpful. And figuring out which can't be done quickly and casually.
As a footnote, a test of the viewing public presumes:
· collecting the result
· toward some end goal.
(Though in saying that, perhaps I'm being heavily led by my bias as someone who constantly runs tests towards end goals, these last 32 years in for-profit R&D.)
My point is that both of these assumptions seem questionable. But perhaps one could collect the results by monitoring reviewers' analyses and social media. And, in rare cases, "curiosity" qualifies as the goal. (I think of "goal" as the core justification for expending the required resources; and modern movies requires inhuman amounts of resources.)