Has the symbol grounding problem
been solved or not?

Minao Kukita
Kyoto University
minao.kukita@gmail.com

Kyoto-NUS Workshop for Applied Philosophy
National University of Singapore
Feb 19, 2014

Today's Goals

To consider how we can and should assess
an approach to the symbol grounding problem

To show what kind of approaches are the best
against the background of
the teleosemantic theory of meaning

Background: Turing vs Searle
If one cannot sufficiently distinguish a machinefrom humans by its external linguistic behaviour,then the machine qualifies as truly intelligent.
``Computing Machinery and Intelligence'' (1950)

A. Turing

J. Searle
If a machine do not understand the meaningof the words it manipulates, thenthe machine cannot be intelligent.
``Minds, Brains, and Programs'' (1980)

Background: Harnad's question
How can symbols manipulated by an AI
be associated with things in the real world?
``The Symbol Grounding Problem'' (1990)

The Symbol Grounding Problem
S. Harnad
Various solutions have been proposed so far.

Solutions to the SGP

It is not sufficient to give a machine a certan semantics
so that a symbol can refer the machine to the object.

It is essential that the machine should generate
its own semantics as it operates in the real world

Taddeo and Floridi's criterion forevaluating various approaches
to the SGP

The Zero Semantical Commitment Condition(Z-condition)
M. Taddeo
Any solution to the SGP should provide semantics that isneither(1) pre-installed into the system, nor(2) external to it,

L. Floridi

but the system should autonomously elaborate its own
semantics from the scratch.

``Solving the Symbol Grounding Problem: a Critical Review of Fifteen Years of Research'' (2005)

Taddeo and Floridi's classification ofapproaches to the SGP●Representationalist– A hybrid model (Harnad 1990)– A functional model (Mayo 2003)– An intentional model (Sun 2000)●

Semi-representationalist– An epistemological model (Davidsson 1995)– The gues game (Steels and Vogt 1997)– A model based on temporal delays and predictive semantics(Rosenstein and Cohen 1998)●

Non-representationalist– A communication-based model (Billard and Dautenhahn 1999)– A behaviour-based model (Varshavskaya 2002)

And their diagnosis thereof●Representationalist– A hybrid model (Harnad 1990)– A functional model (Mayo 2003)– An intentional model (Sun 2000)●Semi-representationalist– An epistemological model (Davidsson 1995)– The gues game (Steels and Vogt 1997)– A model based on temporal delays and predictive semantics(Rosenstein and Cohen 1998)●Non-representationalist

They all presupposes certain semantics– A behaviour-based2002)
and thus model
fail to (Varshavskayameet the Z-condition
according to Taddeo and Floridi– A communication-based model (Billard and Dautenhahn 1999)

Is the Z-condition a reasonable requirement?

The Z-condition precludes, for example,
the use of a neural network or genetic
algorithm because such system involvecommitment to the programmers' semantics.
Moreover, it also precludes learning throughcommunication with agent who is alreadycompetent at a existing language.
But doesn't this render even symbols used byhuman agents ungrounded?

Is the Z-condition a reasonable requirement?

Taddeo and Floridi, in ``A praxical solution of thesymbol grounding problem'' (2008), wrote that thelanguage game described in Wittgenstein'sInvestigation ``clearly do not satisfy the Z-condition.''The Z-condition is too demanding!

Requirements for requirements
for approaches to the SGP
At least humans (and other organisms)
should meet the requirement.
Simple symbol manipulation machines
should not meet the requirement.

Grounded?

UngroundedRequirements for requirements
for approaches to the SGP
At least humans (and other organisms)
should meet the requirement.
Simple symbol manipulation machines
should not meet the requirement.

Grounded?

UngroundedThus we need to articulate the way symbols usedby living organisms are grounded in the first place.

Theory and Model
Theory of Meaning(Hypothesis, Theory)

Validate

Guide

Approach to the SGP(Experiment, Model)

Here is a great chance of philosophers oflanguage and roboticists interacting witheach other in a meaningful way.
Good example of applied philosophy

Teleosemantic theory of meaning

Proposed by R. G. Millikan, teleosemantic
theory of meaning explains how signs usedby living organisms has obtained meaning
through the process of evolution.
According to the theory, if some mechanism
associate a type of events with another, theformer has a semantic mapping relation tothe latter, and becomes a sign for it.

Teleosemantic theory of meaning

According to teleosemantic theory of meaning, anintentional sign has a meaning if
1.there are a producer and consumer of the sign,
2.the production and consumption are carried out
following the normal mechanisms,
3.there is a task to be done by using the sign, and theperformance of the task has some survival value, and4.the sign's having a certain relation to an objects isinvolved in the mechanism of performing the task.

Taddeo and Floridi's classification of
approaches to the SGP●

Representationalist– A hybrid model (Harnad 1990)– A functional model (Mayo 2003)

This is the best.

– An intentional model (Sun 2000)●Semi-representationalist– An epistemological model (Davidsson 1995)– The gues game (Steels and Vogt 1997)– A model based on temporal delays and predictive semantics(Rosenstein and Cohen 1998)●

Non-representationalist– A communication-based model (Billard and Dautenhahn 1999)– A behaviour-based model (Varshavskaya 2002)

Taddeo and Floridi's classification ofapproaches to the SGP●

Representationalist– A hybrid model (Harnad 1990)– A functional model (Mayo 2003)

This is the best.

– An intentional model (Sun 2000)●

Semi-representationalist– An epistemological model (Davidsson 1995)– The gues game (Steels and Vogt 1997)– A model based on temporal delays and predictive semantics(Rosenstein and Cohen 1998)●Non-representationalist
Steels even declared that the SGP has been solved!

– A communication-based model (Billard and Dautenhahn 1999)– A behaviour-based model (Varshavskaya 2002)

Assessment of the guess game approach

According to teleosemantic theory of meaning, anintentional sign has a meaning if
1.there are a producer and consumer of the sign,
2.the production and consumption are carried out
following the normal mechanisms,
3.there is a task to be done by using the sign, and theperformance of the task has some survival value, and4.the sign's having a certain relation to an objects isinvolved in the mechanism of performing the task.

Assessment of the guess game approach

According to teleosemantic theory of meaning, anintentional sign has a meaning if
1.there are a producer and consumer of the sign,
2.the production and consumption are carried out
following the normal mechanisms,
Doubted3.there is a task to be done by using the sign, andtheperformance of the task has some survival value, and4.the sign's having a certain relation to an objects isinvolved in the mechanism of performing the task.

Assessment of the guess game approach

Regarded as violating the Z-condition
According to teleosemantic theory of meaning, anbyhasTaddeoand Floridi
intentional signa meaningif
1.there are a producer and consumer of the sign,
2.the production and consumption are carried out
following the normal mechanisms,Doubted
3.there is a task to be done by using the sign, andtheperformance of the task has some survival value, and4.the sign's having a certain relation to an objects is
involved in the mechanism of performing the task.

The moral here is
We should, at least tentatively, articulate some kind of theoryof meaning when we evaluate approaches to the SGP.
●Adopting the teleosemantic theory of meaning, we can see
the guess game is the best, but we do not think that the SGP
is completely solved.
●This suggests that the success of every approach to the SGP
always comes in degree. Each approach is successful in somedegree, or in some aspects.
●
It is doubtful that any artificial system would have the same
degree of groundedness as human beings or other organisms.
●
It is better to view one approach to the SGP as, like any
scientific model, abstracting such and such aspects of thephenomenon called meaning.
●