UPDATE 2011: There is a new/better version of this essay: “Enactive Interface Perception and Affordances”.
There are two theories of perception which are very interesting to me not just for AI, but also from a point of view of interfaces, interactions, and affordances. The first one is Alva Noë’s enactive approach to perception. The second one is Donald D. Hoffman’s interface theory of perception.
Enactive Perception vs. Interface Perception
The key element of the enactive approach to perception is that sensorimotor knowledge and skills are a required part of perception.
A lot of artificial perception schemes, e.g. for robots, run algorithms on camera video frames. Some programs also use the time dimension, e.g. structure from motion. They can find certain objects and even extract 3D data (especially if they also use a range scanner such as LIDAR, ultrasound, or radar). But the enactive approach suggests that animal visual perception is not simply a transformation of 2-D pictures into a 3-D (or any kind) of representation.
Example of optical flow (one of the ways to get structure from motion). Credit: Naoya Ohta.
My interpretation of the enactive approach is that it suggests perception co-evolved with motor skills such as how our bodies move and how our sensors, for instance, eyes, move. A static 2D image can not tell you what color blobs are objects and what are merely artifacts of the sensor or environment (e.g. light effects). But if you walk around this scene, and take into account how you are moving, you get a lot more data to figure out what is stable and what is not. We have evolved to have constant motion in our eyes via saccades, so even without walking around or moving our heads, we are getting this motion data for our visual perception system.
Of course, there are some major issues that need to be resolved, at least in my mind, about enactive perception (and related theories). As Aaron Sloman has pointed out repeatedly, we need to fix or remove dependence on symbol grounding. Do all concepts, even abstract ones, exist in a mental skyscraper built on a foundation of sensorimotor concepts? I won’t get into that here, but I will return to it in a later blog post.
The enactive approach says that you should be careful about making assumptions that perception (and consciousness) can be isolated on one side of an arbitrary interface. For instance, it may not be alright to study perception (or consciousness) by looking just at the brain. It may be necessary to include much more of the mind-environment system—a system which is not limited to one side of the arbitrary interface of the skull.
Perception as a User Interface
The Interface Theory of Perception says that “our perceptions constitute a species-specific user interface that guides behavior in a niche.”
Evolution has provided us with icons and widgets to hide the true complexity of reality. This reality user interface allows organisms to survive better in particular environments, hence the selection for it.
Perception as an interface
Hoffman’s colorful example describes how male jewel beetles use a reality user interface to find females. This perceptual interface is composed of simple rules involving the color and shininess of female wing cases. Unfortunately, it evolved for a niche which could not have predicted the trash dropped by humans that lead to false positives—which results in male jewel beetles humping empty beer bottles.
Male Australian jewel beetle attempting to mate with a discarded "stubby" (beer bottle). Credit: Trevor J. Hawkeswood.
All perception, including of humans, evolved for adaptation to niches. There is no reason or evidence to suspect that our reality interfaces provide “faithful depictions” of the objective world. Fitness trumps truth. Hoffman says that Noë supports a version of faithful depiction within enactive perception, although I don’t see how that is necessary for enactive perception.
Of course, the organism itself is part of the environment.
True Perception is Right Out the Window
How do we know what we know about reality? There seems to be a consistency at our macroscopic scale of operation. One consistency is due to natural genetic programs—and programs they in turn cause—which result in humans having shared knowledge bases and shared kinds of experience. If you’ve ever not been on the same page as somebody before, then you can imagine how it would be like if we didn’t have anything in common conceptually. Communication would be very difficult. For every other entity you want to communicate with, you’d have to establish communication interfaces, translators, interpreters, etc. And how would you even know who to communicate with in the first place? Maybe you wouldn’t have even evolved communication.
So humans (and probably many other related animals) have experiences and concepts that are similar enough that we can communicate with each other via speech, writing, physical contact, gestures, art, etc.
But for all that shared experience and ability to generate interfaces, we have no inkling of reality.
Since the UI theory says that our perception is not necessarily realistic, and is most likely not even close to being realistic, does this conflict with the enactive theory?
Noë chants the mantra that the world makes itself available to us (echoing some of the 80s/90s era Brooksian “world as its own model”). If representation is distributed in a human-environment system, doesn’t that mean it must be a pretty accurate representation? No. I don’t see why that has to be true. So it seems we can combine the two theories together.
There may be some mutation to enactive theories if we have to slant or expand perception more towards what happens in the environment and away from the morphology-dependent properties. In other words, we may have to emphasize the far environment (everything you can observe or interact with) even more than the near environment (the body). As I think about this and conduct experiments, I will report on how this merging of theories is working out.
Noë, A., Action in Perception, Cambridge, MA: MIT Press, 2004.
Hoffman, D.D, “The interface theory of perception: Natural selection drives true perception to swift extinction” in Dickinson, S., Leonardis, A., Schiele, B., & Tarr, M.J. (Eds.), Object categorization: Computer and human vision perspectives. Cambridge, UK: Cambridge University Press, 2009, pp.148-166. PDF.
Hawkeswood, T., “Review of the biology and host-plants of the Australian jewel beetle Julodimorpha bakewelli,” Calodema, vol. 3, 2005. PDF.