New paper on inference/action-selection – comments welcome

This is a paper I wrote for ICFDG that takes some work from my previous life as a roboticist and applies it to Twig (the procedural animation system I’ve been working on).  However, it’s situated in a tradition that the games community, and even the present-day AI community isn’t very familiar with, so much of the paper is an attempt to survey and explain the literature on using combinational logic for inference – why you’d want to do it, why it’s limited, and what you can do to overcome some of the limitations.  And even then, I’m worried that it won’t be transparent to the reader; not because it’s technically difficult, but just because the motivations won’t be clear.  Anyhow, any advice would be welcome.

fall symposium talk slides

Here are the slides from my position paper at the AAAI Fall Symposium on Naturally Inspired Artificial Intelligence.

Final version of AIIDE paper on procedural animation

This is the revised version of the AIIDE paper on Twig, the procedural animation library I’ve been working on.  I’m going to do a longer journal version of it, so suggestions are very welcome.

Another paper

Men are Dogs (and Women too).  This one’s for the AAAI Fall Symposium on Natural Computation.  It’s my latest effort to try to get my intuitions about cognitive architecture onto paper.  There are a bunch of other arguments that I want to fold into it, but it’s already overdue, so they’ll have to wait for the camera ready copy.  Comments and suggestions welcome.

position paper: ai and psychopathology

I’ve just put up the final version of my position paper for the AAAI Symposium on Intelligent Narrative Technologies.  It argues that popular narratives deal at least as much with the ways characters depart from ideal rationality as it deals with actual rational behavior, that we don’t have computational theories of those modes of behavior, and that we could learn a lot by trying to model them.

make love, not war

I was working yesterday on adding fighting behavior to my procedural character animation.  In particular, I wanted the kids to be able to shove one another around.  But due to a bug they kept approaching one another rather than stopping at “shoving distance.”  So they grapple in what looks like a particularly comical make-out session.  Possibly useful, but best saved for the parent characters…

what is anxiety anyway?

I’ve been trying to think about anxiety recently.  I want to argue that anxiety is part of a broader meta-level control system involved in risk assessment.  The obvious scientific response to this would be something along the lines of “well, duh.”  But I’ve had a great deal of difficulty articulating exactly what I mean to my friends.  So I’m writing this overly long post to try to work through it.  I’ll try using two different analogies, but first I’ll try to give some motivating background.

believability and attributional intentionality

Robot hackers have long realized that human observers tend to over-attribute intelligence, or at least intentionality, to robots, at least provided that they’re moving.  (Dave) Miller’s law states that the perceived intelligence of a robot is directly proportional to its velocity (Dave didn’t name this Miller’s law, but he said it once at a workshop and I’m fond of quoting it).

The image above is a screenshot of what appears to be two child characters playing with one another while being watched by an adult.  However, in actuality, what I’ve been implementing is attachment behavior, which is the response of children to stress by seeking out their caregiver (more on this another day).  To implement that, I need to have something to stress the kids out.  The right way to do it is to implement a real social engagement system with wariness and coy behaviors, play, turn-taking, etc.  However, the first step in that is simply to make a second child and then hack the children’s appraisal systems to assign negative valence to strangers (i.e. to each other).  All that does is make the kids watch one another and keep their distance from one another.  For example, one won’t approach the ball if the other is too close to it.  There’s no real sociality going on there.

The interesting thing is that it’s enough to make them look like they’re playing.  They both run to the ball, but then when one gets to close to it, the other backs off.  The first one will kick it until it happens to kick it toward the other one (which is pretty frequent since I haven’t implemented aiming).  At that point, the first one stays away from the ball and the second one plays with it.  This continues until they get far enough from the parent to engage the attachment system, at which point the attached child runs to the parent and hugs him/her, then runs back to play.

The point of this isn’t that this is a good simulation of anything, just that surprisingly simple behavior can appear engaging and intelligent, provided that whatever behavior you do have is relatively fluent.

the polyvagal theory of the autonomic nervous system

I just finished reading a paper by Stephen Porges on the Polyvagal theory.  It’s very cool.  Here’s my attempt as a non-specialist to summarize it.  The traditional view of the autonomic nervous system is that it has two opposing processes, the sympathetic and the parasympathetic systems, which speed up and slow down the heart, respectively, as well as shifting metabolic resources between organs.  The sympathetic system, which is stimulated in part by the perception of threat, raises heart rate and metabolism, and shifts energy to the brain and muscles, thus preparing the body for a fight-or-flight respond to the perceived thread.  The parasympathetic system acts through the vagus nerve to slow the heart rate and/or shift resources to the gut to aid in digestion.

Porges makes two arguments about the vagal (parasympathetic) system:

• The vagal system isn’t just used for reallocating energy resources during rest and digestion, but it’s also part of the neural substrate for the freeze response (a different, and in fact phylogenetically older, threat response).
• In mammals, the vagal system is split into two systems – the older dorsal system and a newer ventral system.  This newer system is also connected to facials, vocal, and neck muscles, and forms part of the social engagement system, a newer threat response system that’s only present in (social) mammals.

He argues that the autonomic system’s threat responses are organized roughly as a Brooksian subsumption hierarchy, with phylogenetically newer systems overriding older systems in when they conflict.  This is interesting if you’re interested in biologically-based AI because it gives us a much better understanding of the low-level threat-response systems and also shows that social behavior is wired in at surprisingly low levels.

Porges also makes two claims that as far as I can tell are logically independent of the poly-vagal theory, but which are nonetheless interesting.  One is that the (rare) phenomenon of voodoo death, in which people are literally scared to death, is not actually due to overactivation of the sympathetic nervous system overdriving the heart, but rather to the overactivation of the older parasympathetic (in this case, the dorsal system) slowing the heart down to the point where it can no longer supply enough oxygen for itself, much less the brain.  This apparently better matches the experimental results in a rather horrible rat experiment that was done in the 50s.  The claim is that it’s a case of a response that was adaptive for older species being carried over to mammals, in whom it is fatal because of their higher metabolic requirements.

The other claim is based on the observation that there are muscles in the inner ear, which modulate its mechanical properties so as to accentuate or attenuate certain frequencies, in particular, the frequencies associated with the human vocal tract.  He proposes that in at least some cases of developmental disorders involving lack of social engagement, it could be because of understimulation of these muscles, making it harder for children to attend to human voice, and thereby leading to understimulation of the social engagement system.  The description of the experiment in the paper is vague and I haven’t followed up to read the real papers on it, but he found that when he played computer-generated sounds that emphasized frequencies in the range of human speech, most of the children showed “noticable improvements in social behavior and communication skills following the intervention.”  Amazing.