Reasoning with Grounded Self-Symbols for Human-Robot Interaction.

We discuss Perry’s notion of the essential indexical and the requirement that robots interacting with humans (and other robots) be able to reason about themselves in a grounded way. We describe an approach based on grounding symbols via an analogue of the neural mechanism of efference copy and approaching symbolic reasoning via active logic – a situated framework for logical and temporal reasoning. The Essential Indexical Robots that interact with humans should be able to make sense of indexical terms (such as “I” and “now”). For example, a robotic helper should ideally be able to interpret human utterances such as: I am getting hungry. I don’t want to eat now, but would like you to get me a snack from the kitchen in 10 minutes. Please make sure to check that you didn’t spill anything after you’re done, and make sure to clean yourself up too if needed. Understanding such a sentence will require, along with much else, an ability to use indexical notions of “I”, “you”, “now” and “in 10 minutes.” A brief digression into philosophy will demonstrate that this is a more difficult problem than it first appears to be. See (Anderson and Perlis 2005) for a fuller account with explicit ties to robotics. The meat of our digression comes from a seminal 1979 essay by Stanford philosopher John Perry. In it, he describes the peculiar experience of following a trail of sugar around a grocery store. Perry spent some time pushing his cart up the aisle on one side of a tall counter, then down the other, noting all the while that the trail grew thicker and thicker. Eventually the truth dawned on him: as he put it, "I was the shopper I was trying to catch." Perry spent the rest of his seminal paper trying precisely to characterize the changes in his beliefs that precipitated the change in his Copyright © 2016, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved. behavior -which was, of course, that he stopped looking for the shopper with the torn sugar sack. One should like to say that Perry came to believe that “I am the shopper making the mess.” Things turn out not to be so simple. What Perry finds is that in a traditional Fregean framework of de dicto belief -where belief is characterized as a particular relation between a subject and a proposition -there is no room for indexicals like “I” or “now.” For if we accept Perry's construal of the traditional "doctrine of propositions," then we agree that for a proposition S to equal proposition S' is precisely for S and S' to have not only the same truth-value, nor merely the same truth-conditions -that is, merely share the same reference -but that they have also the same intension, or sense. As Perry explains, “Atlanta is the capital of Georgia” and “Atlanta is the capital of the largest state East of the Mississippi” are not the same propositions -though they are certainly true or false under the same conditions -for I can clearly believe one but not the other without inconsistency, depending on what I believe about Georgia1. But then it cannot be that Perry came to believe “I am the shopper with the torn sack,” because that sentence does not even identify a proposition. It is not true or false absolutely. It is ambiguous, depending on who says it. Nor does it help, as Perry points out, to argue that indexicals like “I” or “now” or “this” are communicative shortcuts standing in for some propositions α, β, or γ. For if we claim that all Perry came to believe was, in fact, "α is making a mess," where α unambiguously picks out Perry2, we have not yet explained his subsequent change in behavior -for we also believe this proposition, and yet haven't stopped reading to check our shopping carts. No; Perry must also have believed "I am α." Perry goes on to describe in detail the way in which indexicals like “I” and “now” trouble the waters of tradition1 Hilary Putnam argued against fixing reference in general based solely on truth-conditional criteria. See (Lakoff 1990) for a good exposition. 2 Perhaps, Perry suggests, α might be “the only bearded philosopher in a Safeway store West of the Mississippi.” The 2016 AAAI Fall Symposium Series: Artificial Intelligence for Human-Robot Interaction Technical Report FS-16-01