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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Modeling Theory of Mind in ACTransfer</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Stefan M. Wierda</string-name>
          <email>wierda.stefan@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Burcu Arslan</string-name>
          <email>barslan.cogs@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Institute of Artificial Intelligence, University of Groningen</institution>
          ,
          <addr-line>Groningen</addr-line>
          ,
          <country country="NL">The Netherlands</country>
        </aff>
      </contrib-group>
      <kwd-group>
        <kwd>Theory of Mind</kwd>
        <kwd>ACT-R</kwd>
        <kwd>ACTransfer</kwd>
        <kwd>False-belief task</kwd>
        <kwd>Strategic turn-based games</kwd>
        <kwd>Cognitive Modelling</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Introduction</title>
      <p>
        Does playing strategic games improve your performance on other tasks in which you
have to reason about someone else’s beliefs and intentions, as in for example a
falsebelief task? Both tasks require theory of mind—the ability to reason about someone’s
desires, beliefs, and intentions. In reasoning about others’ minds, we can distinguish
different orders of reasoning. When we reason about the reality (e.g., this abstract),
we talk about zeroth-order theory of mind. First-order theory of mind is when we
reason about someone’s mental states (e.g., I think you find this abstract interesting to
read). Second-order is reasoning about someone who reasons about someone’s mental
states (e.g., I think that you think that I find this abstract interesting to read) and so
forth. Several training studies have shown transfer between first-order theory of mind
tasks [
        <xref ref-type="bibr" rid="ref1 ref2">1,2</xref>
        ]. Thus, training in one task improves performance on a different theory of
mind task—a phenomenon called transfer. However, for higher-order theory of mind,
the amount of transfer between tasks is still unclear. To explore the relation between
two different kinds of tasks that require higher-order theory of mind, the overlap
between two tasks that require second-order theory of mind is investigated.
      </p>
      <p>
        The first task is a turn-based strategy-game called marble drop designed by
Meijering et al. [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] that is played with two players—an orange player and a blue player. In
marble drop, a white marble is dropped onto orange and blue trapdoors that are
controlled by the players that have the corresponding color. Behind each trapdoor, there
is either a second pair of trapdoors or a bin containing a certain number of orange and
blue marbles. The goal is to let the white marble reach the bin that contains the most
marbles of your own color, regardless of the number of marbles the other player gets.
Often you cannot reach the goal by just controlling your own trapdoors. Thus, you
have to reason about the other player’s beliefs, intentions and desires to predict which
trapdoor your opponent is going to open.
      </p>
      <p>The second task is a false-belief task. In a false-belief task, a story is told while
corresponding pictures are presented to the participant. In the story, an item is moved
from one location to the other. This movement is not observed by all characters in the
story. Thus, one or more characters have false beliefs about the location of the item.
After the presentation of the story, participants are asked to reason about the beliefs of
one of the characters in the story. In the story modeled in this study, a mother gives a
piece of chocolate to her son Murat. Her daughter Ayla, who witnesses the gift, gets
angry because she does not get one. Now, Murat puts the chocolate into the drawer
and leaves the scene. Ayla then takes the chocolate out of the drawer and hides it in
the toy box—however, Murat is secretly looking through the window and sees Ayla
hiding the chocolate, without Ayla noticing him. Now, Ayla also leaves the scene and
the mother enters. At the end of the story, the mother finds the chocolate in the toy
box and then puts it near the TV. Participants are then asked where Ayla thinks that
Murat is going to look for the chocolate. To answer this question, second-order theory
of mind is required because the participant has to reason about Ayla’s belief about
Murat’s belief. In this case, Murat thinks that the chocolate is in the toy box, because
he did not see the mother move the chocolate. Ayla however, unaware of the fact that
Murat observed her, thinks that Murat will look in the drawer—the location where he
originally put it. The zeroth-order question in this story is “Where is the chocolate?”
The correct answer to this question is the TV—the location where the mother last put
the chocolate.</p>
      <p>
        In 1901, Woodsworth and Thorndike [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] argued that transfer occurs when two
tasks share identical elements of knowledge. However, they did not specify the
identical elements. Decades later, Singley and Anderson [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] specified the identical
elements as cognitive procedures and showed that transfer occurs when two tasks share
the same procedures. However, the question remained open what the most minimal
procedure looks like. Recently Niels Taatgen [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] proposed the primitive elements
(PRIM). In the PRIM theory, cognitive procedures are broken down into two basic
elements of cognition: the movement of information and the comparison of
information. When learning a task, sequentially executed PRIMs evolve and this results in
task-specific and general elements. When two tasks use the same sequence of PRIMs,
transfer occurs. Here, we model the two abovementioned tasks by using the PRIM
theory to identify whether the marble drop task and the false-belief task require the
same underlying theory of mind strategies.
2
      </p>
    </sec>
    <sec id="sec-2">
      <title>Methods</title>
      <p>
        In this study, an extension of the cognitive architecture ACT-R [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] is used that
implements the PRIM theory (http://www.ai.rug.nl/~niels/actransfer.html). By using
such an architecture, the model inherits the cognitive constrains that the architecture
implements on for example working memory and declarative memory.
      </p>
      <p>
        The model of the marble drop game is based on a forward-reasoning plus
backtracking algorithm [
        <xref ref-type="bibr" rid="ref3 ref8 ref9">3,8,9</xref>
        ]. The model first searches for the highest payoff (forward
reasoning), and then tries to determine whether the payoff is attainable (backtracking).
If a trapdoor of the opponent is encountered during the backtracking phase, the model
switches perspective and then recursively uses the algorithm to determine the best
choice for the other player and so forth.
      </p>
      <p>The model for the false belief task is inspired on the model of Arslan, Taatgen, and
Verbrugge [10]. Whereas their model has all the story facts in its declarative memory,
the current model builds an internal representation as the story is presented. At the
end of the story, it tries to backtrack the actions and observations of each of the
characters. First, the model will come up with a zeroth-order answer, the current location
of the chocolate. Next, the model backtracks the movements of the chocolate and
checks who performed or observed these actions. The model then infers the beliefs of
the characters and answers the question.</p>
      <p>In total, the model was run 20 times in four conditions that each had three blocks
of 40 trials. The first two control conditions consisted of three blocks of the marble
drop game (md-md-md) and three blocks of the false belief task (fb-fb-fb). The last
two transfer conditions consisted of two blocks of the marble game with one block of
the marble drop game in between and vice versa (fb-md-fb and md-fb-md,
respectively). To examine transfer, only log-transformed reaction times of correct trials are
considered. If the difference of the experimental block 2 and control block 3 is
divided by the difference of the control bock 2 and control block 3, the transfer between
the two tasks can be calculated.
The transfer for the false-belief task on the marble drop game is 11.14%. The transfer
for the marble drop game on the false-belief task is 44.2%. As can be seen in Fig. 1,
the last block of the fb-md-fb condition (green line) lies between the second and third
block of the fb-fb-fb condition (red line). A t-test shows that the reaction times indeed
differ for the second control block and the second experimental block (t = -3.67, p &gt;
0.002). In contrast, the error bars of last block in the md-fb-md condition (blue line)
do overlap with the error bars of the second block of the control condition md-md-md
(purple line). Also, a t-test does not reveal any significant differences (t = -0.59, p =
0.563).
4</p>
    </sec>
    <sec id="sec-3">
      <title>Discussion and outlook</title>
      <p>Transfer is found for the marble-drop task onto the false-belief task, but not the other
way around. This finding could be explained by the complexity of both tasks. The
marble drop task is a more complex task and requires more use of the
workingmemory than the false-belief task—thus the model gets more training in specific
working-memory strategies when doing marble drop. For developmental studies, the
difference in complexity might mask transfer-effects. A recent study showed indeed
that there is no transfer from the false-belief task onto the marble-drop game [11].
Whether there is transfer the other way around still remains an open question.</p>
      <p>Further eye-tracking studies could help validate or invalidate proposed models.
Furthermore, learning effects that occur in the last block could potentially inflate the
amount of transfer found. Modelling a non-related task of the similar complexity that
also demand inhibition and recursion could control these issues.
5
of the 12th International Conference on Cognitive Modeling, pp. 1426-1431. Carleton
University, Ottawa (2013)
10. Arslan, B., Taatgen, N.A., Verbrugge, R.: Modeling Developmental Transitions in
Reasoning about False Beliefs of Others. In R. West &amp; Stewart (Eds.), Proceedings of the 12th
International Conference on Cognitive Modeling, pp. 77-82. Carleton University, Ottawa
(2013)
11. Arslan, B., Verbrugge, R., Taatgen, N.A., Hollebrandse, B.: Teaching Children to
Attribute Second-order False Belief: A Training Study. In J. Szymanik &amp; R Verbrugge (Eds.),
Proceedings Second Workshop ‘Reasoning about Other Minds: Logical and Cognitive
Perspectives’: CEUR proceedings. (forthcoming)</p>
    </sec>
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</article>