Cognitive Agents with Commonsense
Antonio Lieto
Università di Torino, Dipartimento di Informatica, IT
ICAR-CNR, Palermo, IT
February 18 2021, iCog seminars, Istituto Italiano di Tecnologia (IIT)

Outline
– Knowledge representation and processing in CAs: Open
problems
– Current Solutions (and their problems): Extended Declarative
Memories
– More Constrained Knowledge Processing Models
– A Case Study on Linguistic Categorization: DUAL-PECCS

Preamble
– Cognitivist Cognitive Architectures are assumed to be well-
equipped in dealing with aspects concerning knowledge processing
and high-level cognition with respect to the emergentist/
developmental ones.
– Unfortunately there are some problems that limit their role in a
computationally grounded science of the mind.

Which role?
4
Inspiration

Which role?
5
Inspiration
Explanation

Knowledge Level Analysis
Knowledge Level (Newell, 1982; 1990) = level of analysis and prediction of the
rational behavior of a cognitive agent (based on the assumed availability of the
agent knowledge, in order to pursue its own goals and related actions).
Can we use the models built in Cognitive Architectures as a computational
proxy of the human knowledge processing capabilities?

Current Problems at the “Knowledge Level”
CAs are general structures without a corresponding “general”
content (SIZE PROBLEM). Ad hoc/task specific built knowledge.
The knowledge represented and manipulated by such CAs is usually
homogeneous in nature (HOMOGENEITY PROBLEM)
Lieto, A., Lebiere, C., & Oltramari, A. (2018). The knowledge level in cognitive architectures: Current
limitations and possible developments. Cognitive Systems Research, 48, 39-55.

SIZE problem
Conceptual knowledge in humans is a huge, variegated and multi-
domain.
To test the architectural mechanisms of memory storage,
retrival, reasoning we should endow our agent with a human-level
knowledge (=> one of Newell’s criteria for a theory of cognition).
Why?
Having a system with huge knowledge poses immediately
computational and cognitive problems concerning the retrieval of
the correct knowledge given a task to solve that are neglected or
hidden under the carpet with toy-knowledge bases.

Solutions: Extended Declarative Memories
- Soar terms connected to the linguistic resource WordNet
but:
only some taxonomical relations
between terms
(Derbinsky et al., 2010)

Solutions: Extended Declarative Memories
- Such solutions are all available in ACT-R
Ball et al. 2008

Solutions: Extended Declarative Memories
- Such solutions are all available in ACT-R
Ball et al. 2008
Salvucci et al. 2014 (DbPedia)

Problems
- All such solutions extends Declarative Memories with symbolic/
ontological semantic representations
- However symbol-like representations encounters problems in
dealing with common-sense knowledge representation and reasoning
(e.g. approximate reasoning is computationally hard in graph-like
structures). (HOMOGENEITY PROBLEM)

(lack of) HETEROGENITY problem
Classical vs Commonsense knowledge
Knowledge represented and manipulated by such CAs mainly the so
called “classical” part of conceptual information (that one
representing concepts in terms of necessary and sufficient
conditions).
The so called “common-sense” conceptual components of our
knowledge is largely absent in such computational frameworks.

Classical Theory – Ex.
22
TRIANGLE = Polygon with 3 corners and sides
PROBLEM: Common-sense concepts cannot be defined in this way.
There are many theories developed in cognitive science trying to
provide an explanation to the problem to typicality

….
AI and CogSci approaches to Commonsense
reasoning (partial overview)
Semantic Networks
(Collins and Quillians, 1969)
Classical
Theory
Prototype Theory
Rosch (1975)
Frames
(Minsky, 1975)
Scripts
(Shank & Abelson,
1977)
Circumscription
(Mc Carthy, 1980)
Exemplar Theory
Medin and Schaffer (1978)

16
Commonsense
knowledge as grounding element of
layers of growing thinking capabilities

17
Commonsense
knowledge as grounding element of
layers of growing thinking capabilities
Commonsense knowledge and
reasoning capabilities

Commonsense reasoning
Concerns all the type of non deductive (or non
monotonic) inference:
- induction
- abduction
- default reasoning
- …
18

Commonsense reasoning
Concerns all the type of non deductive (or non
monotònic) inference:
- induction
- abduction
- default reasoning
- …
19
TIPICALITY

Prototypes and Prototypical Reasoning
• Categories based on prototypes (Rosh,1975)
• New items are compared to the prototype
atypical
typical
P

Ad-hoc Solutions
Use ontologies as frame structures (Misky) or
with “commonsense rules” able to perform
some commonsense inferences

Ad-hoc Solutions
Use ontologies as frame structures (à la
Minsky) or with “commonsense rules” able to
perform some commonsense inferences
BIRD ⊑ FLY

Ad-hoc Solutions
Use ontologies as frame structures (à la
Minsky) or with “commonsense rules” able to
perform some commonsense inferences
BIRD ⊑ FLY
IF X {Wag Tails, Barks, hasFur}

Ad-hoc Solutions
Use ontologies as frame structures (à la
Minsky) or with “commonsense rules” able to
perform some commonsense inferences
BIRD ⊑ FLY
IF X {Wag Tails, Barks, hasFur}

Problems
This knowledge engineering approach works
for well-defined narrow domains but it is does
not scale and is not generalizable.

Problems
This knowledge engineering approach works
for well-defined narrow domains but it is does
not scale and is not generalizable.
Why? Prototypes and Commonsense
knowledge dynamic and context dependent.

Problems
typical

Problems
typical

Exemplars and Exemplar-based Reasoning
• Categories as composed by a list of exemplars. New
percepts are compared to known exemplars (not to
Prototypes).

Conflicting Theories?
• Exemplars theory overcomes the Prototypes (it can
explain so called OLD ITEM EFFECT).
• Still in some situations prototypes are preferred in
categorization tasks.
30

Conflicting Theories?
• Exemplars theory overcomes the Prototypes (it can
explain so called OLD ITEM EFFECT).
• Still in some situations prototypes are preferred in
categorization tasks.
Prototypes, Exemplars and other conceptual
representations (for the same concept) can co-exists
and be activated in different contexts (Malt 1989).
31

Type 1/Type 2 features
32
ACT-R
(Anderson et
al. 2004)
CLARION (Sun,
2006)
Vector-LIDA
(Franklin et al.
2014)
SOAR (Laird
2012)
Concepts as chunks
(symbolic
structures)
Neural networks +
Symbol Like
representations
High dimensional
vector spaces
Concepts as chunks
(symbolic
structures)
Sub-symbolic and
Bayesian
activation of chunks
Subsymbolic
activation of
conceptual chunks
Similarity based
vectorial activation
Rule-based
activation and firing
of chunks
Prototypes and
Exemplars models
of categorisation
available in
separation
Prototypes and
Exemplars models
of categorisation
NOT available
Prototypes and
Exemplars models
of categorisation
NOT available
Prototypes and
Exemplars models
of categorisation
NOT available
Extended
Declarative Memory
CYC, DBPedia)
Ad hoc or narrow
Knowledge
Ad hoc or narrow
Knowledge
Extended Semantic
Memory with
linguistic resources
(ex. Wordnet)

DUAL PECCS: DUAL- Prototype and Exemplars
Conceptual Categorization System
Lieto, Radicioni, Rho (IJCAI 2015, JETAI 2017)

34
1) Multiple representations for the same concept
2) On such diverse, but connected, representation are executed
different types of reasoning (System 1/ System 2) to integrate.
2 Cognitive Assumptions
Type 1 Processes Type 2 Processes
Automatic Controllable
Parallel, Fast Sequential, Slow
Pragmatic/contextualized
…
Logical/Abstract
…

Heterogeneous Proxytypes Hypothesis
The different proposals that have been advanced can be grouped in three main classes: a) fuzzy approaches, b) probabilistic and Bayesan approaches, c) approaches based on
non-monotonic formalisms.
TIPICALITY
The diverse types of connected representations can coexist and point to
the same conceptual entity. Each representation can be activated as a proxy
(for the entire concept) from the long term memory to the working memory of
a cognitive agent.
(Lieto, A. A Computational Framework for Concept Representation in Cognitive Systems and
Architectures: Concepts as Heterogeneous Proxytypes, Proc. of BICA 2014)
CLASSICAL

Ex. Heterogeneous Proxytypes at work
The different proposals that have been advanced can be grouped in three main classes: a) fuzzy approaches, b) probabilistic and Bayesan approaches, c) approaches based on
non-monotonic formalisms.
(Lieto, A. A Computational Framework for Concept Representation in Cognitive Systems and
Architectures: Concepts as Heterogeneous Proxytypes, Proc. of BICA 2014)

Heterogeneous Proxytypes in DUAL-PECCS
37
dopting differ-
mbolic perspec-
oded in terms
orks [Quillian,
prototypes can
convex region
mbolic perspec-
concept can, on
atterns of con-
Ns). Similarly,
both symbolic
sed, as well as
emplars can be
mbolic systems,
or as a partic-
inally, also for
t in principle–,
ver, this seems
evels are more
nceptual repre-
tificial systems
is-a: feline
color: yellow
hasPart: fur
hasPart: tail
hasPart: stripes
...
conceptual space
representation
concept Tiger
Kingdom: Animalia
Class: Mammalia
Order: Carnivora
Genus: Panthera
Species: P. tigris
prototype of Tiger exemplars of Tiger
white-tiger
is-a: feline
color: white
hasPart: fur
hasPart: tail
hasPart: stripes
...
...
ontological
representation
classical information
Typicality-based
knowledge
Classical
knowledge
Hybrid Knowledge Base
Figure 1: Heterogeneous representation of the tiger concept
our system includes two main sorts of components, based on
Lieto, A., Radicioni, D., Rho, V, (2017). Dual PECCS: a cognitive system for conceptual
representation and categorization, JETAI, 29 (2), 433-452, Taylor and Francis.
Lieto et al. (2015), A Common-Sense Conceptual Categorization System Integrating
Heterogeneous Proxytypes and the Dual Process of Reasoning, IJCAI, AAAI Press.

38
ng differ-
perspec-
in terms
Quillian,
types can
ex region
perspec-
pt can, on
s of con-
Similarly,
symbolic
s well as
rs can be
systems,
a partic-
also for
inciple–,
is seems
are more
al repre-
systems
is-a: feline
color: yellow
hasPart: fur
hasPart: tail
hasPart: stripes
...
conceptual space
representation
concept Tiger
Kingdom: Animalia
Class: Mammalia
Order: Carnivora
Genus: Panthera
Species: P. tigris
prototype of Tiger exemplars of Tiger
white-tiger
is-a: feline
color: white
hasPart: fur
hasPart: tail
hasPart: stripes
...
...
ontological
representation
classical information
Typicality-based
knowledge
Classical
knowledge
Hybrid Knowledge Base
Figure 1: Heterogeneous representation of the tiger concept
our system includes two main sorts of components, based on
Co-referring representational Structures via Wordnet
Lieto, A., Mensa, E,, Radicioni, D., 2016. A resource-driven approach for anchoring linguistic resources
conceptual spaces. In Conference of the Italian Association for Artificial Intelligence (pp. 435-449). Springer, Cham.

S1/S2 Categorization Algorithms
39

Overview
NL Description
-The big fish eating plankton
Typical
Representations
IE step and
mapping
List of Concepts :
-Whale 0.1
-Shark 0.5
-…
Output S1
(Prototype or
Exemplar)
Check on S2
Ontological Repr.
-Whale NOT Fish
-Whale Shark OK
Output S2 (CYC)
Output S1 + S2
Whale
Whale Shark

ACT-R Integration
• “Extended” Declarative
Memory of ACT-R
• Integration of the dual
process base categorisation
processes in ACT-R
41
for a given concept can be represented by adopting differ-
ent computational frameworks: i) from a symbolic perspec-
tive, prototypical representations can be encoded in terms
of frames [Minsky, 1975] or semantic networks [Quillian,
1968]; ii) from a conceptual space perspective, prototypes can
be geometrically represented as centroids of a convex region
(more on this aspect later); iii) from a sub-symbolic perspec-
tive, the prototypical knowledge concerning a concept can, on
the other hand, be represented as reinforced patterns of con-
nections in Artificial Neural Networks (ANNs). Similarly,
for the exemplars-based body of knowledge, both symbolic
and conceptual space representations can be used, as well as
the sub-symbolic paradigm. In particular, exemplars can be
represented as instances of a concept in symbolic systems,
as points in a geometrical conceptual space, or as a partic-
ular (local) pattern of activation in a ANN. Finally, also for
the classical body of knowledge it is –at least in principle–,
is-a: feline
color: yellow
hasPart: fur
hasPart: tail
hasPart: stripes
...
conceptual space
representation
concept Tiger
Kingdom: Animalia
Class: Mammalia
Order: Carnivora
Genus: Panthera
Species: P. tigris
prototype of Tiger exemplars of Tiger
white-tiger
is-a: feline
color: white
hasPart: fur
hasPart: tail
hasPart: stripes
...
...
ontological
representation
classical information
Typicality-based
knowledge
Classical
knowledge
Hybrid Knowledge Base
ACT-R concepts represented as en “empty
chunk” (chunk having no associated information,
except for its WordNet synset ID and a human
readable name), referred to by the external bodies
of knowledge (prototypes and exemplars) acting
like semantic pointers.

CLARION Integration
• “Extende
42
for a given concept can be represented by adopting differ-
ent computational frameworks: i) from a symbolic perspec-
tive, prototypical representations can be encoded in terms
of frames [Minsky, 1975] or semantic networks [Quillian,
1968]; ii) from a conceptual space perspective, prototypes can
be geometrically represented as centroids of a convex region
(more on this aspect later); iii) from a sub-symbolic perspec-
tive, the prototypical knowledge concerning a concept can, on
the other hand, be represented as reinforced patterns of con-
nections in Artificial Neural Networks (ANNs). Similarly,
for the exemplars-based body of knowledge, both symbolic
and conceptual space representations can be used, as well as
the sub-symbolic paradigm. In particular, exemplars can be
represented as instances of a concept in symbolic systems,
as points in a geometrical conceptual space, or as a partic-
ular (local) pattern of activation in a ANN. Finally, also for
the classical body of knowledge it is –at least in principle–,
is-a: feline
color: yellow
hasPart: fur
hasPart: tail
hasPart: stripes
...
conceptual space
representation
concept Tiger
Kingdom: Animalia
Class: Mammalia
Order: Carnivora
Genus: Panthera
Species: P. tigris
prototype of Tiger exemplars of Tiger
white-tiger
is-a: feline
color: white
hasPart: fur
hasPart: tail
hasPart: stripes
...
...
ontological
representation
classical information
Typicality-based
knowledge
Classical
knowledge
Hybrid Knowledge Base
• natively “dual process”
• Typicality information (conceptual space
—> implicit NACS layer
• Classical (ontology)—> explicit NACS
The mapping between the sub-symbolic module of
CLARION and the vector-based representations of the
Conceptual Spaces has been favored, since such
architecture also synthesizes the implicit information in
terms of dimensions-values pairs

ACT-R, SOAR, CLARION and LIDA Extended Declarative Memories with
DUAL-PECCS
Salvucci et al. 2014 (DbPedia)

DEMO https://www.youtube.com/watch?v=1KtnAWyxj-8
44

http://dualpeccs.di.unito.it

Evaluation
The different proposals that have been advanced can be grouped in three main classes: a) fuzzy approaches, b) probabilistic and Bayesan approaches, c) approaches based on non-monotonic
formalisms.
112 common sense linguistic descriptions provided by a team of linguists,
philosophers and neuroscientists interested in the neural basis of lexical
processing (FMRI).
Gold standard: for each description recorded the human answers for the
categorization task.
Stimulus Expected
Concept
Expected Proxy-
Representation
Type of Proxy-
Representation
… … … …
The primate
with red nose
Monkey Mandrill EX
The feline with
black fur that
hunts mice
Cat Black cat EX
The big feline
with yellow fur
Tiger Prototypical
Tiger
PR

47
• Two evaluation metrics have been devised:
- Concept Categorization Accuracy: estimating how often the
correct concept has been retrieved;
- Proxyfication Accuracy: how often the correct concept has
been retrieved AND the expected representation has been
retrieved, as well.
Accuracy Metrics

48
• Three sorts of proxyfication errors were committed:
- Ex-Proto, an exemplar is returned in place of a prototype;
- Proto-Ex, we expected a prototype, but a prototype is
returned;
- Ex-Ex, an exemplar is returned differing from the
expected one.
• Three sorts of proxyfication errors were committed:
- Ex-Proto, an exemplar is returned in place of a prototype;
- Proto-Ex, we expected a prototype, but a prototype is
returned;
- Ex-Ex, an exemplar is returned differing from the
expected one.
Proxyfication Error

Analysis
The different proposals that have been advanced can be grouped in three main classes: a) fuzzy approaches, b) probabilistic and Bayesan approaches, c) approaches based on non-monotonic
formalisms.
- The comparison of the obtained results with human
categorization is encouraging 77-89% (results of other
AI systems for such reasoning tasks are by far lower).
- The analysis of the results revealed that it is not true
that exemplars (if similar enough to the stimulus to
categorise) are always preferred w.r.t. the
prototypes.
- Need of a more fine-grained theory explaining more in
the details the interaction between co-existing
representations in the heterogeneous hypothesis.

Upshots and Future direction
The different proposals that have been advanced can be grouped in three main classes: a) fuzzy approaches, b) probabilistic and Bayesan approaches, c) approaches based on non-monotonic
formalisms.
Cognitive architectures should be endowed with more
constrained knowledge processing mechanisms to test their
representational and reasoning assumptions (commonsense as
crucial component).
Commonsense could be the “bridge” between perception and
cognition.
Need to find non ad-hoc integration solutions.
The mechanisms showed could influence other components
(e.g. episodic memory & exemplars; affordances & prototypes) in
an integrated architecture.

Cognitive Design for Artificial Minds
51
Forthcoming in 2021 !!
Taylor and Francis
Forthcoming in April 2021 !!
Taylor and Francis