Knowledge Creation through Multimodal Communication

Knowledge Creation through Multimodal
Communication
Marcus Berliant

and Masahisa Fujita
Washington University in St. Louis and Kyoto University

May 17, 2024

Knowledge Creation through Multimodal Communication

Thank you for having me in to visit and attending this talk.
Thank you Mori-sensei for your hospitality.
Please feel free to interrupt with questions/comments/jokes
at any time.
This is the second presentation of this paper. It has changed
drastically since the …rst presentation.
Now about that …rst presentation...

Knowledge Creation through Multimodal Communication

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Knowledge Creation as a Square Dance on the Hilbert Cube
(Main, in the International Economic Review )Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Knowledge Creation as a Square Dance on the Hilbert Cube
(Main, in the International Economic Review )The Dynamics of Knowledge Diversity and Economic Growth(Application, in the Southern Economic Journal)

Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Knowledge Creation as a Square Dance on the Hilbert Cube
(Main, in the International Economic Review )The Dynamics of Knowledge Diversity and Economic Growth(Application, in the Southern Economic Journal)
Culture and Diversity in Knowledge Creation (Application
with cites to religious texts, Regional Science and Urban
Economics)

Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Knowledge Creation as a Square Dance on the Hilbert Cube
(Main, in the International Economic Review )The Dynamics of Knowledge Diversity and Economic Growth(Application, in the Southern Economic Journal)
Culture and Diversity in Knowledge Creation (Application
with cites to religious texts, Regional Science and Urban
Economics)
This paper
Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

There are now π + 2 papers completed in this project:
Dynamics of Knowledge Creation and Transfer: The Two
Person Case (Elementary, in International Journal of
Economic Theory )Knowledge Creation as a Square Dance on the Hilbert Cube
(Main, in the International Economic Review )The Dynamics of Knowledge Diversity and Economic Growth(Application, in the Southern Economic Journal)
Culture and Diversity in Knowledge Creation (Application
with cites to religious texts, Regional Science and Urban
Economics)
This paper
AI paper? Now over 200 pages.
Copies of the papers are available, e.g. from my web page.
There will be lots of pictures today.

Knowledge Creation through Multimodal Communication

Expositional Note

The papers are long and have quite a bit of algebra in them.
That is because we prove everything analytically. This paper
is 86 pages short.

Knowledge Creation through Multimodal Communication

Expositional Note

The papers are long and have quite a bit of algebra in them.
That is because we prove everything analytically. This paper
is 86 pages short.
In contrast, it is easy to present this work quickly using only
pictures, including both the statement of results and idea of
proofs. You just have to get the hang of it.

Knowledge Creation through Multimodal Communication

Expositional Note

The papers are long and have quite a bit of algebra in them.
That is because we prove everything analytically. This paper
is 86 pages short.
In contrast, it is easy to present this work quickly using only
pictures, including both the statement of results and idea of
proofs. You just have to get the hang of it.
There will be a minimum of notation and lots of pictures andhand waving.

Knowledge Creation through Multimodal Communication

Abstract from First Paper:

COUPLE 1

FACING
COUPLEBACK T O
MINI-WAVEBACK DANCERS (LEFT HAND)

FACING COUPLESBACK TO BACK OCEAN WAVE OCEAN WAVE
(RIGHT HAND) (LEFT HAND)
COUPLESRIGHT HAND BOX
CIRCULATE

T WO FACE LINE
(RIGHT HAND) ST AT IC SQUARESINGLE FILE
PROM ENADE ALAM O STYLECIRCLELEFT HAND BOX
CIRCULATE

Source: http://www.penrod-sq-dancing.com/fasr1.html

What do you know about square dancing? It’s a metaphor...

Knowledge Creation through Multimodal Communication

Abstract from First Paper:

COUPLE 1

FACING
COUPLEBACK T O
MINI-WAVEBACK DANCERS (LEFT HAND)

FACING COUPLESBACK TO BACK OCEAN WAVE OCEAN WAVE
(RIGHT HAND) (LEFT HAND)
COUPLESRIGHT HAND BOX
CIRCULATE

T WO FACE LINE
(RIGHT HAND) ST AT IC SQUARESINGLE FILE
PROM ENADE ALAM O STYLECIRCLELEFT HAND BOX
CIRCULATE

Source: http://www.penrod-sq-dancing.com/fasr1.html

What do you know about square dancing? It’s a metaphor...
This was the abstract, until Masa decided that we had to get
serious. (Me, serious?)Knowledge Creation through Multimodal Communication

Abstract from First Paper:

COUPLE 1

FACING
COUPLEBACK T O
MINI-WAVEBACK DANCERS (LEFT HAND)

FACING COUPLESBACK TO BACK OCEAN WAVE OCEAN WAVE
(RIGHT HAND) (LEFT HAND)
COUPLESRIGHT HAND BOX
CIRCULATE

T WO FACE LINE
(RIGHT HAND) ST AT IC SQUARESINGLE FILE
PROM ENADE ALAM O STYLECIRCLELEFT HAND BOX
CIRCULATE

Source: http://www.penrod-sq-dancing.com/fasr1.html

What do you know about square dancing? It’s a metaphor...
This was the abstract, until Masa decided that we had to get
serious. (Me, serious?)
I’m not Masa, so you will have to settle for second best.

Knowledge Creation through Multimodal Communication

Abstract from First Paper:

COUPLE 1

FACING
COUPLEBACK T O
MINI-WAVEBACK DANCERS (LEFT HAND)

FACING COUPLESBACK TO BACK OCEAN WAVE OCEAN WAVE
(RIGHT HAND) (LEFT HAND)
COUPLESRIGHT HAND BOX
CIRCULATE

T WO FACE LINE
(RIGHT HAND) ST AT IC SQUARESINGLE FILE
PROM ENADE ALAM O STYLECIRCLELEFT HAND BOX
CIRCULATE

Source: http://www.penrod-sq-dancing.com/fasr1.html

What do you know about square dancing? It’s a metaphor...
This was the abstract, until Masa decided that we had to get
serious. (Me, serious?)
I’m not Masa, so you will have to settle for second best.
The …rst line describes the process of writing these papers.

Knowledge Creation through Multimodal Communication

Outline of this Talk

I. Motivation and related literature
II.
The model basics for all of the papers
Short Rest
III.
The Model with 2 persons in the stationary stateIV.
E¤ect of F2F lead time on the mode of communication andjoint knowledge productivity
V.
Knowledge composition, productivity, and choice of work
mode
VI.
Dynamics of the two-person system
VII.
Summary, correcting ine¢ ciencies, extensions
Don’t worry, each section is short!

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Questions About Knowledge Creation

How should the process of knowledge creation be modeled?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Questions About Knowledge Creation

How should the process of knowledge creation be modeled?
How does the knowledge creation process function when there
are multiple ways for people to communicate, for example face
to face or using the internet?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Questions About Knowledge Creation

How should the process of knowledge creation be modeled?
How does the knowledge creation process function when there
are multiple ways for people to communicate, for example face
to face or using the internet?
Relative to the one communication channel case, whatdi¤erent patterns of joint research among knowledge workers
emerge, and how is the productivity of research work a¤ected?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Questions About Knowledge Creation

How should the process of knowledge creation be modeled?
How does the knowledge creation process function when there
are multiple ways for people to communicate, for example face
to face or using the internet?
Relative to the one communication channel case, whatdi¤erent patterns of joint research among knowledge workers
emerge, and how is the productivity of research work a¤ected?
Under what conditions are the conceptual and technicalphases of knowledge production best accomplished througheach of the communication channels?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.
What are the e¢ ciency consequences of tacit knowledge?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.
What are the e¢ ciency consequences of tacit knowledge?
What kind of innovation policy is appropriate in the presenceof tacit knowledge?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.
What are the e¢ ciency consequences of tacit knowledge?
What kind of innovation policy is appropriate in the presenceof tacit knowledge?
Can arti…cial intelligence have tacit knowledge?

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.
What are the e¢ ciency consequences of tacit knowledge?
What kind of innovation policy is appropriate in the presenceof tacit knowledge?
Can arti…cial intelligence have tacit knowledge?
To address these questions, we must …rst build a model thatincorporates tacit knowledge.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Motivation: Tacit Knowledge
When analyzing the dynamics of knowledge creation, as we dohere, the concept of tacit knowledge among the people
creating new knowledge arises organically.
As tacit knowledge is the part of knowledge that is not
manifested in the …nal product, readers will recognize it as
what is learned by authors in the academic research settingthat is not explicitly embedded in a published paper, including
this one.
What are the e¢ ciency consequences of tacit knowledge?
What kind of innovation policy is appropriate in the presenceof tacit knowledge?
Can arti…cial intelligence have tacit knowledge?
To address these questions, we must …rst build a model thatincorporates tacit knowledge.
We are not aware of any formal models of either multimodal
communication or tacit knowledge in the prior literature.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Essential Features:

History matters, agents changeKnowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Essential Features:

History matters, agents change
Too much in common ! not enough originality, low
productivity

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Essential Features:

History matters, agents change
Too much in common ! not enough originality, low
productivity
Too little in common ! communication di¢ cult, low
productivity

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Essential Features:

History matters, agents change
Too much in common ! not enough originality, low
productivity
Too little in common ! communication di¢ cult, low
productivity
Endogenous Agent Heterogeneity - Horizontal

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

On the one hand:
Whether working alone or with others, a person’s accumulated
knowledge base might not be compatible with that of anotherperson with whom they’ve had no contact.
On the other hand:
If two people have been working together for a long time, theirbase of knowledge in common increases, and their partnership
eventually becomes less productive.
We investigate the permanent e¤ects of knowledge creation andgrowth.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation

Useful Analogy

Working jointly to share ideas and create new onesmPartner dancing(For now, 3 or 4 cannot dance together, though couples can dance
simultaneously.)
People can work or dance alone.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Motivation(Macro Models)

.&
.&

.&

# # # #
True Microfoundations(We Are Trying to Get Here)A Robot Economist?

(Our Work)Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview of the Results

Deterministic Framework

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview of the Results

Deterministic Framework
Myopic Agents

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview of the Results

Deterministic Framework
Myopic Agents
In contrast with our previous work, here we separate theknowledge creation process into conceptual and technicalphases, and allow researchers to choose the mode ofcommunication, F2F or the net, that suits them best in eachphase.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Modes of Communication

Figure 1. Knowledge creation through multiple modes ofcommunication

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Main Results
1First, we …nd that a crucial parameter in the model is the leadtime for F2F communication. What we mean by lead time is
the …xed cost for communicating F2F, such as the cost ofcommuting to the o¢ ce.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Main Results
1

2First, we …nd that a crucial parameter in the model is the leadtime for F2F communication. What we mean by lead time is
the …xed cost for communicating F2F, such as the cost ofcommuting to the o¢ ce.
Second, in contrast with our previous work, the steady state
will not, in general, be the state with highest productivity.
The net e¤ect is that achieving and maintaining the highest
productivity pro…le of knowledge in common and di¤erential
knowledge requires more heterogeneity or larger researchgroups than we found in our previous work.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Main Results
1

2

3

First, we …nd that a crucial parameter in the model is the leadtime for F2F communication. What we mean by lead time is
the …xed cost for communicating F2F, such as the cost ofcommuting to the o¢ ce.
Second, in contrast with our previous work, the steady state
will not, in general, be the state with highest productivity.
The net e¤ect is that achieving and maintaining the highest
productivity pro…le of knowledge in common and di¤erential
knowledge requires more heterogeneity or larger researchgroups than we found in our previous work.
Third, the e¤ect of tacit knowledge on knowledge productivity
is not internalized by the knowledge workers.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Main Results
1

2

3

4

First, we …nd that a crucial parameter in the model is the leadtime for F2F communication. What we mean by lead time is
the …xed cost for communicating F2F, such as the cost ofcommuting to the o¢ ce.
Second, in contrast with our previous work, the steady state
will not, in general, be the state with highest productivity.
The net e¤ect is that achieving and maintaining the highest
productivity pro…le of knowledge in common and di¤erential
knowledge requires more heterogeneity or larger researchgroups than we found in our previous work.
Third, the e¤ect of tacit knowledge on knowledge productivity
is not internalized by the knowledge workers.
Fourth, as net and transport technology improves, knowledge
composition becomes more important than geographicaldistance in the choice of research partners.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Application to Covid Restrictions (Appendix
A)

Applying this framework to pandemic restrictions, we show,for example, how the productivity of knowledge workers withlonger commutes to work is a¤ected less than those withshorter commutes when pandemic restrictions on face to facework are implemented.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Preview of the Results

Preview: Application to Covid Restrictions (Appendix
A)

Applying this framework to pandemic restrictions, we show,for example, how the productivity of knowledge workers withlonger commutes to work is a¤ected less than those withshorter commutes when pandemic restrictions on face to facework are implemented.
This application requires the introduction of multimodal
communication to our model.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.
See paper for literature review

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.
See paper for literature review
Part of our framework here is based on the insightful empirical
paper by Lin et al (2022).

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.
See paper for literature review
Part of our framework here is based on the insightful empirical
paper by Lin et al (2022).
They break down the knowledge creation process into
conceptual and technical phases.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.
See paper for literature review
Part of our framework here is based on the insightful empirical
paper by Lin et al (2022).
They break down the knowledge creation process into
conceptual and technical phases.
The early conceptual phase involves tacit knowledge
deployment, whereas the later technical phase involves explicit
knowledge.

Knowledge Creation through Multimodal Communication
Motivation and Related Literature
Related Literature

Related Literature
Covid, etc.
See paper for literature review
Part of our framework here is based on the insightful empirical
paper by Lin et al (2022).
They break down the knowledge creation process into
conceptual and technical phases.
The early conceptual phase involves tacit knowledge
deployment, whereas the later technical phase involves explicit
knowledge.
Using a large data set, they …nd that face to facecommunication is more e¤ective in the conceptual phase,whereas remote teams can be e¤ective in the technical phase.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Basic Model - Previous Papers: What is an Idea?
This Paper

Recipe for Udon Noodles... ∞Everyone can read the labels, but it takes time to learn thecontents (it takes no time to read the labels).

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Basic Model - Previous Papers: What is an Idea?
This Paper

Recipe for Udon Noodles... ∞Everyone can read the labels, but it takes time to learn thecontents (it takes no time to read the labels).
Ideas are ordered (k)Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Basic Model - Previous Papers: What is an Idea?
This Paper

Recipe for Udon Noodles... ∞Everyone can read the labels, but it takes time to learn thecontents (it takes no time to read the labels).
Ideas are ordered (k)Time is continuous (R+ )Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Basic Model - Previous Papers: What is an Idea?
This Paper

Recipe for Udon Noodles... ∞Everyone can read the labels, but it takes time to learn thecontents (it takes no time to read the labels).
Ideas are ordered (k)Time is continuous (R+ )1 if person i knows idea k at time txik (t ) =0 otherwise

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Basic Model - Previous Papers: What is an Idea?
This Paper

Recipe for Udon Noodles... ∞Everyone can read the labels, but it takes time to learn thecontents (it takes no time to read the labels).
Ideas are ordered (k)Time is continuous (R+ )1 if person i knows idea k at time txik (t ) =0 otherwise
Knowledge of person i at time t :Ki (t ) = (xi1 (t ), xi2 (t ), ...) 2 f0, 1g∞ (Speci…es set of ideas
known by person i at time t.)

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Knowledge Creation

Creation of new ideas alone - dancing alone: Opening a box
not opened previously by anyone.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Knowledge Creation

Creation of new ideas alone - dancing alone: Opening a box
not opened previously by anyone.
Joint creation of new ideas: Opening a box not opened
previously by anyone together. Becomes knowledge incommon.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Knowledge Creation

Creation of new ideas alone - dancing alone: Opening a box
not opened previously by anyone.
Joint creation of new ideas: Opening a box not opened
previously by anyone together. Becomes knowledge incommon.
All take time. Opportunity cost is time in this model.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Hilbert Cube = [0, 1]H where H = f1, 2, 3, ...gSo for all i, for all t, Ki (t ) is a vertex of the Hilbert cube.
For our analysis today, we treat ideas symmetrically, so we don’t
need to know Ki (t ), but only some statistics about Ki (t ):# of ideas known by i at t:∞

ni (t ) = ∑ xik (t )k =1

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Hilbert Cube = [0, 1]H where H = f1, 2, 3, ...gSo for all i, for all t, Ki (t ) is a vertex of the Hilbert cube.
For our analysis today, we treat ideas symmetrically, so we don’t
need to know Ki (t ), but only some statistics about Ki (t ):# of ideas known by i at t:∞

ni (t ) = ∑ xik (t )k =1# of ideas known by both i and j at t:∞

nijc (t ) = ∑ xik (t ) xjk (t )k =1

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The Hilbert Cube = [0, 1]H where H = f1, 2, 3, ...gSo for all i, for all t, Ki (t ) is a vertex of the Hilbert cube.
For our analysis today, we treat ideas symmetrically, so we don’t
need to know Ki (t ), but only some statistics about Ki (t ):# of ideas known by i at t:∞

ni (t ) = ∑ xik (t )k =1# of ideas known by both i and j at t:∞

nijc (t ) = ∑ xik (t ) xjk (t )k =1# of ideas known by i but not by j at t:
nijd (t ) = ni (t )nijc (t )Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The 2 Person Model: Choices

Consider 2 agents.
If either does not want to meet, then no meeting occurs.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

The 2 Person Model: Choices

Consider 2 agents.
If either does not want to meet, then no meeting occurs.
If both want to meet, then there is a meeting. Myopic core.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Framework above is useful for explaining the model. Whatfollows are the real assumptions. All rates are per unit oftime:Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Framework above is useful for explaining the model. Whatfollows are the real assumptions. All rates are per unit oftime:
Individual Production:yi (t ) = ni (t ) = felicity

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Framework above is useful for explaining the model. Whatfollows are the real assumptions. All rates are per unit oftime:
Individual Production:yi (t ) = ni (t ) = felicity
New ideas created alone at t:
α ni ( t )Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Framework above is useful for explaining the model. Whatfollows are the real assumptions. All rates are per unit oftime:
Individual Production:yi (t ) = ni (t ) = felicity
New ideas created alone at t:
α ni ( t )New ideas created jointly with a meeting at t:hi 31
β nijc (t ) nijd (t ) njid (t )Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Framework above is useful for explaining the model. Whatfollows are the real assumptions. All rates are per unit oftime:
Individual Production:yi (t ) = ni (t ) = felicity
New ideas created alone at t:
α ni ( t )New ideas created jointly with a meeting at t:hi 31
β nijc (t ) nijd (t ) njid (t )Best = Even Split - % common ideas, % ideas exclusive to i,% ideas exclusive to j. Overlap for communication, but
agents are di¤erent. Originality. Like Masa and Marcus, theyknow di¤erent stu¤. Functional form more general in manyof the papers.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Agents are myopic. Their only choice is meeting or not.
Choose option with higher increase in rate of output:
dy /dty
If tied:

max

max

d
dt

dy /dtyKnowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Agents are myopic. Their only choice is meeting or not.
Choose option with higher increase in rate of output:
dy /dty
If tied:

max

max

d
dt

dy /dty

The perfect foresight version of the model is di¢ cult, but wehave some results with it.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Divide all endogenous variables (“n”) by the total # of ideas(for both) to obtain normalized variables “m”, interpreted aspercentages.
mc + mijd + mjid = 1

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Divide all endogenous variables (“n”) by the total # of ideas(for both) to obtain normalized variables “m”, interpreted aspercentages.
mc + mijd + mjid = 1
Know mijd , mjid =) know mc

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Divide all endogenous variables (“n”) by the total # of ideas(for both) to obtain normalized variables “m”, interpreted aspercentages.
mc + mijd + mjid = 1
Know mijd , mjid =) know mc
We are now within δ of having all the notation. Most
everything else will be pictures.

Knowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Divide all endogenous variables (“n”) by the total # of ideas(for both) to obtain normalized variables “m”, interpreted aspercentages.
mc + mijd + mjid = 1
Know mijd , mjid =) know mc
We are now within δ of having all the notation. Most
everything else will be pictures.
δ = 0 () No meetingKnowledge Creation through Multimodal Communication
The Model Basics for All of the Papers

Divide all endogenous variables (“n”) by the total # of ideas(for both) to obtain normalized variables “m”, interpreted aspercentages.
mc + mijd + mjid = 1
Know mijd , mjid =) know mc
We are now within δ of having all the notation. Most
everything else will be pictures.
δ = 0 () No meetingδ = 1 () MeetingKnowledge Creation through Multimodal Communication
A Short Rest

A Short Rest - The Arch

Knowledge Creation through Multimodal Communication
A Short Rest

Cardinals

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

The Model with 2 Persons in the Stationary State

Figure 2. The activity tree for knowledge creation by person i in
Isolation.

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Figure 3. The activity tree for joint knowledge creation

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary StateThe Structure of One Period - JOINT Work

Conceptual

Independent

Technical

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead TimeλCF = Time spent in Conceptual work Face to faceKnowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead TimeλCF = Time spent in Conceptual work Face to face
λCN = Time spent in Conceptual work on the Net

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead TimeλCF = Time spent in Conceptual work Face to face
λCN = Time spent in Conceptual work on the Net
The two persons can jointly choose λCF and λCN freely,
subject to the following constraint:(1 + εF ) λCF + λCN = 1, λCF

0, λCN0where εF > 0 represents the lead time of joint thinking forconceptual development F2F.

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead TimeλCF = Time spent in Conceptual work Face to face
λCN = Time spent in Conceptual work on the Net
The two persons can jointly choose λCF and λCN freely,
subject to the following constraint:(1 + εF ) λCF + λCN = 1, λCF

0, λCN0where εF > 0 represents the lead time of joint thinking forconceptual development F2F.
In practice, εF re‡ects the time cost of preparing for a F2F
meeting, such as commuting time to the common CBD o¢ ce(or common university), or travel time between two cities or
two countries where each of the two persons reside separately.

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead TimeλCF = Time spent in Conceptual work Face to face
λCN = Time spent in Conceptual work on the Net
The two persons can jointly choose λCF and λCN freely,
subject to the following constraint:(1 + εF ) λCF + λCN = 1, λCF

0, λCN0where εF > 0 represents the lead time of joint thinking forconceptual development F2F.
In practice, εF re‡ects the time cost of preparing for a F2F
meeting, such as commuting time to the common CBD o¢ ce(or common university), or travel time between two cities or
two countries where each of the two persons reside separately.
Lead time for Net is normalized to zero.

Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead Time

Face 2 Face
Conceptual Sub-Period

RemoteKnowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead Time

Face 2 Face

RemoteConceptual Sub-Period

Lead Time

Face 2 Face
Technical Sub-Period

RemoteKnowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead Time

Face 2 Face

RemoteConceptual Sub-Period

Lead Time

Face 2 Face

RemoteTechnical Sub-Period
Workers can choose % mode of communication in each
Sub-Period: F2F (at work) and Remote (at home)Knowledge Creation through Multimodal Communication
The Model with 2 Persons in the Stationary State

Lead Time

Face 2 Face

RemoteConceptual Sub-Period

Lead Time

Face 2 Face

RemoteTechnical Sub-Period
Workers can choose % mode of communication in each
Sub-Period: F2F (at work) and Remote (at home)
Covid restrictions limit the sum total of F2F acrossConceptual and Technical sub-periods.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivityE¤ect of F2F lead time on the mode of communicationand joint knowledge productivity
Assumption 1. In both the phase of conceptual development
and the phase of technical development, thinking jointly F2F
is more e¤ective than thinking jointly through the Net.
Furthermore, the e¤ectiveness of F2F relative to the Net isgreater in conceptual development than in technicaldevelopment.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivityE¤ect of F2F lead time on the mode of communicationand joint knowledge productivity
Assumption 1. In both the phase of conceptual development
and the phase of technical development, thinking jointly F2F
is more e¤ective than thinking jointly through the Net.
Furthermore, the e¤ectiveness of F2F relative to the Net isgreater in conceptual development than in technicaldevelopment.
This assumption is based on two ideas. First, tacit knowledge
is best developed and exploited face to face. Nonaka and
Takeuchi (1995) provide case studies, including the inventionof the …rst automatic home bakery machine by Matsushita
and the development of the City car model by Honda. Bothinvolved the exploitation of tacit knowledge. Second,
empirical evidence developed by Lin et al (2022) is consistent
with this assumption.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

Figure 4. The parameter value of F2F lead-time and the threeranges ofcommunication mode εF when αCF /αCN = 2 and ατF /ατN = 1.5.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

Figure 5. h (εF ) is the relative productivity of joint work at εF incomparison with the productivity of joint work at εF = 0 over thethree ranges of parameter εF .

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

No Net Technology

Figure 5 can be interpreted as representing the impact of thedevelopment of net-communication technology, where thebroken curve represents the relative productivity at each εF
when no net-technology is available, whereas the real curve
represents the relative productivity under the e¤ective use ofmodern net-technology.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

No Net Technology

Figure 5 can be interpreted as representing the impact of thedevelopment of net-communication technology, where thebroken curve represents the relative productivity at each εF
when no net-technology is available, whereas the real curve
represents the relative productivity under the e¤ective use ofmodern net-technology.
The case where no net-technology is available is studied byInoue et al (2022), since the internet didn’t exist during the
Spanish ‡u epidemic.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

No Net Technology

Figure 5 can be interpreted as representing the impact of thedevelopment of net-communication technology, where thebroken curve represents the relative productivity at each εF
when no net-technology is available, whereas the real curve
represents the relative productivity under the e¤ective use ofmodern net-technology.
The case where no net-technology is available is studied byInoue et al (2022), since the internet didn’t exist during the
Spanish ‡u epidemic.
Without this substitute for F2F, the e¤ect on knowledge
creation was severe.

Knowledge Creation through Multimodal CommunicationE¤ect of F2F lead time on the mode of communication and joint knowledge productivity

Figure 6. The impact of the advancement of net-technology on therelative productivity curveKnowledge Creation through Multimodal Communication
Knowledge composition, productivity, and choice of work mode

Knowledge composition, productivity, and choice ofwork mode

To understand stu¤ graphically, it’s useful to look at the symmetricstates:mijd = mjid = md
Once symmetric, always symmetric.

Knowledge Creation through Multimodal Communication
Knowledge composition, productivity, and choice of work mode

Figure 7. The knowledge growth rate curve gJ (md ) and the Bliss
Point mB .

Knowledge Creation through Multimodal Communication
Knowledge composition, productivity, and choice of work mode

Figure 8. Knowledge growth rate curves gJ (md ; εF ) forεF = 0 < εF < εCF , sharing the same Bliss Point mB , and the shareof di¤erential knowledge for each of three potential partners.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Dynamics of the two-person system

Figure 9. The dynamics of two-person system whenmE < m̃ < mB .

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Tacit Knowledge

Next we shall de…ne tacit knowledge and then explain how it arises
in our context. The the ideas behind “tacit knowledge” originate
with Polanyi (1958). Polanyi (1966, p.4) famously states, “We
can know more than we can tell.”Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Tacit Knowledge“...we classify human knowledge into two kinds. One is
explicit knowledge, which can be articulated in formal
language including grammatical statements,
mathematical expressions, speci…cations, manuals, and soforth. This kind of knowledge can be transmitted acrossindividuals formally and easily. This has been thedominant mode of knowledge in the Western
philosophical tradition. However, we shall argue, a more
important type of knowledge is tacit knowledge, which is
hard to articulate with formal language. It is personal
knowledge embedded in individual experience andinvolves intangible factors such as personal belief,
perspective, and the value system. Tacit knowledge has
been overlooked as a critical component of collective
human behavior.” Nonaka and Takeuchi (1995, p. viii)

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Figure 10. Dual dynamics of formal-K and total-K for thetwo-person system.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

The presence of tacit knowledge causes this.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

The presence of tacit knowledge causes this.
The di¤erence between the two switching rules becomes clear
when we consider this situation in the context of the academic
world.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

The presence of tacit knowledge causes this.
The di¤erence between the two switching rules becomes clear
when we consider this situation in the context of the academic
world.
An evaluation committee always faces the di¢ cult problem of
how to evaluate the contribution of each author when papers
are written jointly.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

The presence of tacit knowledge causes this.
The di¤erence between the two switching rules becomes clear
when we consider this situation in the context of the academic
world.
An evaluation committee always faces the di¢ cult problem of
how to evaluate the contribution of each author when papers
are written jointly.
A simple, drastic rule would be that when a paper is writtenby 2 authors, the contribution of each author just equals one
half of the contribution of the paper.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

In the actual academic world, however, an evaluationcommittee tends to adopt a more generous rule.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

In the actual academic world, however, an evaluationcommittee tends to adopt a more generous rule.
That is, if we consider e¢ cient growth of the total knowledgeof each (young) researcher in the long-run, when a paper iswritten by 2 persons, the evaluation committee is justi…ed toallocate much more than one half of the paper’s contribution
to each author.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Switch Point

In the actual academic world, however, an evaluationcommittee tends to adopt a more generous rule.
That is, if we consider e¢ cient growth of the total knowledgeof each (young) researcher in the long-run, when a paper iswritten by 2 persons, the evaluation committee is justi…ed toallocate much more than one half of the paper’s contribution
to each author.
That is because tacit knowledge accumulates during theknowledge production process; such knowledge is invisible in
the …nal product, namely the paper itself.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Sink Point

There is only one other potential partner, and the partners
become too similar (md is too small).

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Sink Point

There is only one other potential partner, and the partners
become too similar (md is too small).
This happens even if there is no tacit knowledge.

Knowledge Creation through Multimodal Communication
Dynamics of the two-person system

Ine¢ ciency in Sink Point

There is only one other potential partner, and the partners
become too similar (md is too small).
This happens even if there is no tacit knowledge.
Need a Square Dance.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Summary
Building on our earlier work, we have developed a model ofknowledge creation in the context of two persons when
multiple modes of communication are available, andknowledge workers can independently use the internet for the
purpose of search.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Summary
Building on our earlier work, we have developed a model ofknowledge creation in the context of two persons when
multiple modes of communication are available, andknowledge workers can independently use the internet for the
purpose of search.
Departing from our earlier model based on modelingknowledge creation as a single activity, we have elaborated theentire process of joint knowledge creation as an activity tree.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Summary
Building on our earlier work, we have developed a model ofknowledge creation in the context of two persons when
multiple modes of communication are available, andknowledge workers can independently use the internet for the
purpose of search.
Departing from our earlier model based on modelingknowledge creation as a single activity, we have elaborated theentire process of joint knowledge creation as an activity tree.
It has been shown that with the advancement of net
technology, joint knowledge creation can be conducted over awide range of geographical area without losing muchproductivity.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Summary
Building on our earlier work, we have developed a model ofknowledge creation in the context of two persons when
multiple modes of communication are available, andknowledge workers can independently use the internet for the
purpose of search.
Departing from our earlier model based on modelingknowledge creation as a single activity, we have elaborated theentire process of joint knowledge creation as an activity tree.
It has been shown that with the advancement of net
technology, joint knowledge creation can be conducted over awide range of geographical area without losing muchproductivity.
Tacit knowledge, missing from earlier models, plays a hugerole in our analysis of the dynamics of the system.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

2 sources of ine¢ ciency in the modelKnowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

2 sources of ine¢ ciency in the modelE¢ cient growth of total knowledge requires that the switchfrom working in isolation to joint work should occur muchearlier, where the growth rate of total knowledge per person in
joint work is equal to the growth rate of total knowledge inisolated work.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

2 sources of ine¢ ciency in the modelE¢ cient growth of total knowledge requires that the switchfrom working in isolation to joint work should occur muchearlier, where the growth rate of total knowledge per person in
joint work is equal to the growth rate of total knowledge inisolated work.
To remedy the ine¢ ciency caused by a myopic switching rule
based on per capita output of patent production, a publicagent may subsidize a signi…cant portion of the revenue frompatent-sales.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

Second, a more interesting and more important ine¢ ciency isthat the growth rate of formal-K at the sink point issigni…cantly lower than at the Bliss Point.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

Second, a more interesting and more important ine¢ ciency isthat the growth rate of formal-K at the sink point issigni…cantly lower than at the Bliss Point.
When the research partners are in a low-productivity sinkpoint trap, what possible mechanism could enable the partners
to escape from this trap and attain much higher productivity?

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Correcting Ine¢ ciencies

Second, a more interesting and more important ine¢ ciency isthat the growth rate of formal-K at the sink point issigni…cantly lower than at the Bliss Point.
When the research partners are in a low-productivity sinkpoint trap, what possible mechanism could enable the partners
to escape from this trap and attain much higher productivity?
Answer: A modi…ed square danceKnowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Extensions
It is our hope, more generally, that the model of knowledge
creation through multimodal communication developed in thispaper can be extended and applied in a broader context suchas e¢ cient development of international academic societies in
the age of rapidly developing ICT and AI.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Extensions
It is our hope, more generally, that the model of knowledge
creation through multimodal communication developed in thispaper can be extended and applied in a broader context suchas e¢ cient development of international academic societies in
the age of rapidly developing ICT and AI.
It would be of interest to allow other forms of agent
heterogeneity, such as large and small city residents, or CBD
and suburban residents.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Extensions
It is our hope, more generally, that the model of knowledge
creation through multimodal communication developed in thispaper can be extended and applied in a broader context suchas e¢ cient development of international academic societies in
the age of rapidly developing ICT and AI.
It would be of interest to allow other forms of agent
heterogeneity, such as large and small city residents, or CBD
and suburban residents.
Intergenerational transmission of knowledge and improvements
in internet search productivity due to the increasing stock ofknowledge over time should be investigated.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Extensions
It is our hope, more generally, that the model of knowledge
creation through multimodal communication developed in thispaper can be extended and applied in a broader context suchas e¢ cient development of international academic societies in
the age of rapidly developing ICT and AI.
It would be of interest to allow other forms of agent
heterogeneity, such as large and small city residents, or CBD
and suburban residents.
Intergenerational transmission of knowledge and improvements
in internet search productivity due to the increasing stock ofknowledge over time should be investigated.
To sum up, there is much further work to be done to analyze
the microeconomic dynamics of knowledge creation in settings
with tacit knowledge and multiple modes of communication.

Knowledge Creation through Multimodal Communication
Summary, correcting ine¢ ciencies, extensions

Time to sing?