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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>R. 2012. Leakproofing the Singularity Arti-
ficial Intelligence Confinement Problem. Journal of Con</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">0304-3975</issn>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Performance of Bounded-Rational Agents With the Ability to Self-Modify*</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Jakub Teˇtek</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Marek Sklenka</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Tom a´sˇ Gavencˇiak</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>University of Copenhagen j.tetek@gmail.com</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>University of Oxford sklenka.marek@gmail.com</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Independent researcher gavento@ucw.cz</string-name>
        </contrib>
      </contrib-group>
      <pub-date>
        <year>2014</year>
      </pub-date>
      <issue>2015</issue>
      <fpage>483</fpage>
      <lpage>492</lpage>
      <abstract>
        <p>Self-modification of agents embedded in complex environments is hard to avoid, whether it happens via direct means (e.g. own code modification) or indirectly (e.g. influencing the operator, exploiting bugs or the environment). It has been argued that intelligent agents have an incentive to avoid modifying their utility function so that their future instances work towards the same goals. Everitt et al. (2016) formally show that providing an option to self-modify is harmless for perfectly rational agents. We show that this result is no longer true for agents with bounded rationality. In such agents, self-modification may cause exponential deterioration in performance and gradual misalignment of a previously aligned agent. We investigate how the size of this effect depends on the type and magnitude of imperfections in the agent's rationality (1-4 below). We also discuss model assumptions and the wider problem and framing space. We examine four ways in which an agent can be boundedrational: it either (1) doesn't always choose the optimal action, (2) is not perfectly aligned with human values, (3) has an inaccurate model of the environment, or (4) uses the wrong temporal discounting factor. We show that while in the cases (2)-(4) the misalignment caused by the agent's imperfection does not increase over time, with (1) the misalignment may grow exponentially.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>
        We face the prospect of creating superhuman (or otherwise
very powerful) AI systems in the future where those
systems hold significant power in the real world
        <xref ref-type="bibr" rid="ref4">(Bostrom 2014;
Russell 2019)</xref>
        . Building up theoretical foundations for the
study and design of such systems gives us a better chance to
align them with our long-term interests. In this line of work,
we study agent-like systems, i.e. systems optimizing their
actions to maximize a certain utility function – the
framework behind the current state-of-the-art reinforcement
learning systems and one of the major proposed models for future
AI systems1.
      </p>
      <p>If strong AI systems with the ability to act in the real
world are ever deployed2, it is very likely that they will have
some means of deliberately manipulating their own
implementation, either directly or indirectly (e.g. via
manipulating the human controller, influencing the development of a
future AI, exploiting their own bugs or physical limitations
of the hardware, etc). While the extent of those means is
unknown, even weak indirect means could be extensively
exploited with sufficient knowledge, compute, modelling
capabilities and time.</p>
      <p>Omohundro (2008) argues that every intelligent system
has a fundamental drive for goal preservation, because when
the future instance of the same agent strives towards the
same goal, it is more likely that the goal will be achieved.
Therefore, Ohomundro argues, a rational agent should never
modify into an agent optimizing different goals.</p>
      <p>
        <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
        examine this question formally and
arrive at the same conclusion: that the agent preserves its
goals in time (as long as the agent’s planning algorithm
anticipates the consequences of self-modifications and uses the
current utility function to evaluate different futures).3
However, Everitt’s analysis assumes that the agent is a perfect
utility maximizer (i.e. it always takes the action with the
greatest expected utility), and has perfect knowledge of the
environment. These assumptions are probably unattainable
in any complex environment.
      </p>
      <p>
        To address this, we present a theoretical analysis of a
selfmodifying agent with imperfect optimization ability and
incomplete knowledge. We model the agent in the standard
1Other major models include e.g. comprehensive systems of
services
        <xref ref-type="bibr" rid="ref8">(Drexler 2019)</xref>
        and ”Oracle AI” or ”Tool AI”
        <xref ref-type="bibr" rid="ref1">(Armstrong, Sandberg, and Bostrom 2012)</xref>
        . However, there are
concerns and ongoing research into the emergence of agency in these
systems (Omohundro 2008; Miller, Yampolskiy, and Ha¨ggstro¨m
2020).
      </p>
      <p>
        2Proposals to prevent this include e.g. boxing
        <xref ref-type="bibr" rid="ref4">(Bostrom 2014)</xref>
        but as e.g. Yampolskiy (2012) argues, this may be difficult or
impractical.
      </p>
      <p>
        3
        <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
        ’s results hold independent of the length of
the time horizon or temporal discounting (by simple utility
scaling).
cybernetic model where the agent can be bounded-rational
in two different ways. Either the agent makes suboptimal
decisions (is a bounded-optimization agent) or has
inaccurate knowledge. We conclude that imperfect optimization
can lead to exponential deterioration of alignment through
self-modification, as opposed to bounded knowledge, which
does not result in future misalignment. An informal
summary of the results is presented below.
      </p>
      <p>Finally, we explicitly list and discuss the underlying
assumptions that motivate the theoretical problem and
analysis. In addition to clearly specifying the scope of
conclusions, the explicit problem assumptions can be used as a
rough axis to map the space of viable research questions in
the area; see Sections 2 and 6.
1.1</p>
    </sec>
    <sec id="sec-2">
      <title>Summary of our results</title>
      <p>
        The result of
        <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
        could be loosely
interpreted to imply that agents with close to perfect rationality
would either prefer not to self-modify, or would self-modify
and only lose a negligible target value.
      </p>
      <p>We show that when we relax the assumption of perfect
rationality, their result no longer applies. The bounded-rational
agent may prefer to self-modify given the option and in
doing so, become less aligned and lose a significant part of the
attainable value according to its original goals.</p>
      <p>We use the difference between the attainable and attained
expected future value at an (arbitrarily chosen) future time
point as a proxy for the degree of the agent’s misalignment
at that time. Specifically, for a future time t, we consider
the value attainable from time t (after the agent already ran
and self-modified for t time units), and we estimate the loss
of value f t relative to the non-modified agent in the same
environment state. Note that f t is not pre-discounted by the
previous t steps. See Section 3 for formal definitions and
Section 2 for motivation and discussion.</p>
      <p>We consider four types of deviation from perfect
rationality, see Section 4 for formal definitions.
• -optimizers make suboptimal decisions.
• -misaligned agents have inaccurate knowledge of the
human utility function.
• -ignorant agents have inaccurate knowledge of the
environment.
• -impatient agents have inaccurate knowledge of the
correct temporal discount function.</p>
      <p>Note that for the sake of simplicity, we use a very simple
model of bounded rationality where the errors are simply
bounded by the error parameters ; this has to be taken into
account when interpreting the results. However, we suspect
that the asymptotic dependence of value loss on the size of
errors and time would be similar for a range of natural,
realistic models of bounded rationality.</p>
    </sec>
    <sec id="sec-3">
      <title>Informal result statements</title>
      <p>Self-modifying -optimizers may deteriorate in future
alignment and performance exponentially over time, losing
exponential amount of utility compared to -optimizers that do
not self-modify. We show upper and tight lower bounds (by
a constant) on the worst-case value loss in Theorem 7. As
we decrease (increase discounting), the rate at which the
agent’s performance deteriorates increases and the
possibility of self-modification becomes a more serious problem.</p>
      <p>
        Our analysis of bounded-optimization agents is a
generalization of Theorem 16 from
        <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
        in the sense
that their result can be easily recovered by a basic
measuretheoretic argument.
      </p>
      <p>Self-modifying u-misaligned, -ignorant, or -impatient
perfect optimizers can only lose the same value as
non-selfmodifying agents with the same irrationality bounds. This
also holds for any combination of the three types of bounded
knowledge. We give tight upper and lower bounds (up to a
constant factor) for the worst-case performance. See
Section 5.2 for details.</p>
      <p>This implies that unlike bounded-optimization agents, the
performance of perfect-optimization bounded-knowledge
agents does not deteriorate in time. This is because
boundedknowledge agents continue to take optimal actions with
respect to their almost correct knowledge and do not
selfmodify in a way that would worsen their performance in
their view. Therefore, the possibility of self-modification
seems less dangerous in the case of bounded-knowledge
agents than in the case of bounded-optimization agents.
A self-modifying agent with any combination of the four
irrationality types may lose value exponential in the time step
t when the agent optimization error parameter o &gt; 0. We
again give tight (up to a constant factor) lower bounds on the
worst-case performance of such agents. See Section 5.3 for
details.</p>
      <p>Our results do not imply that every such agent will
actually perform this poorly but the prospect of exponential
deterioration is worrying in the long-term, even if it happens
at a much slower speed than suggested by our results. We
focus on worst-case analysis because it tells us whether we can
have formal guarantees of the agent’s behaviour – a highly
desirable property for powerful real-world autonomous
systems, including a prospective AGI (artificial general
intelligence) or otherwise strong AIs.</p>
      <p>Overview of formal results. Here we summarize how much
value the different types of bounded-rational agents may
lose via misalignment. Note that the maximal attainable
discounted value is at most 1 1 and the losses should be
considered relative to that, or to the maximum attainable value
in concrete scenarios. Otherwise, the values for different
value of are incomparable. In all cases, the worst-case
lower and upper bounds are tight up to a constant.
-optimizer agents – bounded optimization, after t steps of
possible self-modification (Theorem 7)
fotpt( ; ) = min( t 1 ; 1
1
)
-misaligned agents – inaccurate utility (Theorem 9)
futil( ; ) =
-impatient agents – inaccurate discounting (Theorem 13)
Here is the correct discount factor and is the agent’s
incorrect discount factor.
1</p>
      <p>)
2
(1</p>
      <p>1</p>
      <sec id="sec-3-1">
        <title>Assumptions and rationale</title>
        <p>Both the statement of the problem and its relevance to AI
alignment rest on a set of assumptions listed below. While
this list is non-exhaustive, we try to cover the main implicit
and explicit choices in our framing, and the space of
alternatives. This is largely in hope of eventually finding a better,
more robust theoretical framework for solving agent
selfmodification within the context of AI alignment, but even
further negative results in the space would inform our
intuitions on what aspects of self-modification make the
problem harder.</p>
        <p>
          We propose consideration of various assumptions as a
framework for thinking about prospective realistic agent
models that admit formal guarantees. We invite further
research and generalizations in this area, one high-level goal
being to map a part of the space of agent models and
assumptions that do or do not permit guarantees, eventually
finding agent models that do come with meaningful
guarantees. Further negative results would inform our intuitions on
what aspects of the problems make it harder.
(i) Bounded rationality model. In the models of
-boundedrational agents defined in Section 4.1, is generally an
upper bound on the size of the optimization or knowledge
error. One interpretation of our results is that value drift
can happen even if the error is bounded at every step. One
could argue that a more realistic scenario would assume
some distribution of the size of the errors, assuming larger
errors less likely or less frequent; see discussion below
and in Section 6.
(ii) Unlimited self-modification ability. We assume the agent
is able to perform any self-modification at any time. This
models the worst-case scenario when compared to a
limited but still perfectly controlled self-modification.
However, embedded (non-dualistic) agents in complex
environments may chieve almost-unlimited self-modification
from a limited ability, e.g. over a longer time span; see
e.g.
          <xref ref-type="bibr" rid="ref6">(Demski and Garrabrant 2019)</xref>
          . We model the agent’s
self-modifications as orthogonal to actions in the
environment.
(iii) Modification-independence. We assume that the agent’s
utility function does not explicitly reward or punish
selfmodifications. We also assume that self-modifications do
not have any direct effect on the environment. This is
captured by Definition 2.
(iv) No corrigibility mechanisms. We do not consider systems
that would allow human operators to correct the system’s
goals, knowledge or behaviour. The problem of robust
strong AI corrigibility is far from solved today and this
paper can be read as a further argument for substantially
more research in this direction.
(v) Worst-case analysis and bound tightness. We focus on
worst-case performance guarantees in abstracted models
rather than e.g. full distributional analysis, and we show
that our worst-case bounds are attainable (up to constant
factors) under certain agent behaviour. Note this approach
may turn out as too pessimistic or even impossible in
some settings (e.g. quantum physics).
(vi) Bounded value attainable per time unit. We assume the
agent obtains instantaneous utility between 0 and 1 at
each time step. This is not an arbitrary choice: A constant
bound on instantaneous value can be normalized to this
interval. Instantaneous values bounded by a function of
time U (t) &lt; t can be pre-discounted when &lt; 1, and
generally lead to infinite future values otherwise, which
we disallow here to avoid foundational problems.
(vii) Temporal value discounting. We assume the agent
employs some form of temporal value discounting. This
could be motivated by technical or algorithmic
limitations, increasing uncertainty about the future, or to avoid
issues with incomparable infinite values of considered
futures (see
          <xref ref-type="bibr" rid="ref3">Bostrom (2011)</xref>
          for a discussion of infinite
ethics). Discounting, however, contrasts with the
longtermist view; see the discussion below.
(viii) Exponential discounting. Our model assumes the agent
discounts future utility exponentially, a standard
assumption in artificial intelligence and the only time-invariant
discounting schema (Strotz 1955) leading to consistent
preferences over time.
(ix) Unbounded temporal horizons. Our analysis focuses on
the long-term behaviour of the agent, in particular
stability and performance from the perspective of future
stakeholders (sharing the original utility function). Note that
our results also to some extent apply to finite-horizon but
long-running systems.
        </p>
        <p>Temporal discounting contrasts with the long-termist
view: Why not model non-discounted future utility
directly? Noting the motivations we mention in (vii), we
agree that models of future value aggregation other than
discounting would be generally better suited for long-term
objectives. However, this seems to be a difficult task, as
such models are neither well developed nor currently used
in open-ended AI algorithms (with the obvious exception
of a finite time horizon, which we propose to explore in
Section 6).</p>
        <p>We therefore propose a direct interpretation of our results:
Assuming we implement agents that are -optimizers with
discounting, they may become exponentially less aligned
over time. This is not the case with perfect optimizers with
imperfect knowledge and discounting.
(x) Dualistic setting. We assume a dualistic agent and allow
self-modification through special actions. This allows us
to formally model one aspect of embedded agency – at
least until there are sufficient theoretical foundations of
embedded agency.</p>
        <p>
          Note that in the embedded (non-dualistic) agent setting, it
is not formally clear – or possibly even definable – what
constitutes a self-modification, since there is no clear
conceptual boundary between the agent and the environment,
as discussed by
          <xref ref-type="bibr" rid="ref6">Demski and Garrabrant (2019)</xref>
          .
        </p>
        <p>Assumption categories and the problem space. Each
assumption identifies a subspace of research questions we
would obtain by varying the relevant choices. These
subspaces vary from very technical (e.g. concrete rationality
model) to foundational (e.g. finite values and dualistic agent
models). Along this axis, the assumptions and choices point
to different kinds of prospective problems; we briefly
describe three such categories and their prospects. See
Section 6 for concrete proposals of future work.</p>
        <p>Technical choices: A concrete model of bounded
rationality, unlimited self-modification model, and
modificationindependence. These are likely important for short and
medium time-frames, where even eventually-diverging
guarantees are useful.</p>
        <p>We believe that many models within some realistic and
sufficiently strong model classes would lead to qualitatively
equivalent results in long time horizons; e.g. the agent
divergence would be asymptotically exponential without external
corrigibility, embedded agents in sufficiently complex
environments would be able to self-modify arbitrarily over a
long time (see discussion above) etc. However, these
intuitions call for further verification.</p>
        <p>Problem components: No corrigibility mechanisms,
unbounded time horizon, time-invariant temporal discounting,
focus on the worst-case guarantees. For those, there are
interesting alternatives that may yield more optimistic results.
In particular, it would be valuable to explore formal models
of corrigibility, perform a full probabilistic analysis of agent
development, and develop long-term non-discounted
finitetime settings.</p>
        <p>Foundational assumptions: Dualistic agent model and
finite value of the future. Those are a standard in the area,
but alternative settings may open up important and fruitful
model classes and technical choices that capture currently
pre-paradigmatic aspects (e.g. theory of embedded agency
and non-dualistic agents).</p>
        <p>3</p>
      </sec>
      <sec id="sec-3-2">
        <title>Preliminaries</title>
        <p>
          In this section, we explain our model of a self-modifying
agent, which is borrowed from
          <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
          . We will
extend this model to include bounded rationality in
Section 4.
        </p>
        <p>We use a modified version of the standard cybernetic
model. In this model, an agent interacts with the
environment in discrete time steps. At each time step t, the agent
performs an action at from a finite set A and the
environment responds with a perception et from a finite set E . An
action-perception pair aet is an action concatenated with
a perception. A history is a sequence of action-perception
pairs ae1ae2:::aet. We will often abbreviate such sequences to
ae&lt;t = ae1:::aet 1 or aen:m = aen:::aem. A complete history
ae1:1 is a history containing information about all the time
steps.</p>
        <p>An agent can be described by its policy . The policy4
: (A E ) ! A is used to determine the agent’s next
action from the history at time t. We consider
(boundedrational) utility maximizers, where the policy is (partially)
determined by the instantaneous utility function u, belief
and discount factor . We sometimes use the notation
= (u; ; ), where is called the agent’s knowledge. The
utility function u~ : (A E )1 ! R describes how much the
agent prefers the complete history ae1:1 compared to other
complete histories. We will assume that the total utility is a
discounted sum of instantaneous utilities given by the
instantaneous utility function u : (A E ) ! [0; 1]. Formally,
u~(ae1:1) = Pt1=1 t 1u(ae t). The discount factor
describes how much the agent prefers immediate reward
compared to the same reward at a later time. Smaller means
heavier discounting of the future and stronger preference for
immediate reward. Note that the maximum achievable utility
is 1 1 , which happens when u(aet) = 1 at each step. Also
note that instantaneous utility depends not only on the latest
perception but can also depend on all previous perceptions
and actions.</p>
        <p>In addition to all this, an agent has a belief : (A E )
A ! E where E is the set of full-support
probability distributions over E . This is a function which maps any
history ending with an action onto a probability
distribution over the next perceptions. Intuitively speaking, the
belief describes what the agent expects to see after it
performs an action given a certain history. A belief together
with a policy induce a measure on the set (A E ) using
P (et j ae&lt;tat) = (et j ae&lt;tat) and P (at j ae&lt;t) = 1
if (ae&lt;t) = at and 0 otherwise. Intuitively speaking, this
probability measure captures probabilities assigned by the
agent to possible futures.</p>
        <p>Following the reinforcement learning literature, we define
the value function V : (A E ) ! R as the expected future
discounted utility:</p>
        <p>1
V (ae&lt;t) = E[ X</p>
        <p>t0 tu(ae&lt;t0 ) ]
t0=t
The expectation value on the right is calculated with respect
to belief and assuming the agent will follow the policy .
Intuitively, the value function describes how promising the
future seems. When the value V (ae&lt;t) of a history is high,
it means we can expect an agent with policy to collect a
lot of utility in the future starting from this history. Note that
when calculating V-values, instantaneous utilities are
multiplied by t0 t rather than t0 . This means that V-values
can remain high throughout the whole history and are not
affected by discounting. We define the Q-value of an action
as the expected future discounted utility after taking that
ac4For a set S, S denotes the set of finite sequences of elements
from S</p>
        <p>Q (ae&lt;tat) = E[u(ae1:t) + V (ae1:t)]
where the expectation is over the next perception drawn
from the belief (note that belief is a probability distribution)</p>
        <p>The Q-value measures how good an action is given that
the agent will later follow policy . A policy is an optimal
policy when V (ae&lt;t) = sup V (ae&lt;t) for all histories
ae&lt;t (such a policy always exists, as shown in (Lattimore
and Hutter 2014)).
3.1</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>Self-modification model</title>
      <p>In this section, we extend the formalism above to include the
possibility of self-modification. Since we are interested in
the worst-case scenario, we assume the agent has unlimited
self-modification ability. Worst-case results derived for such
an agent will also hold for agents with limited ability to
selfmodify.</p>
      <p>Definition 1. A policy self-modification model is defined as
a quadruple (A; E ; P; ) where A is the set of world actions,
E is the set of perceptions, P is a non-empty set of names
and is a map from P to the set of all policies .</p>
      <p>At every time step, the agent chooses an action at =
(at; pt+1) from the set A = (A P). The first part at
describes what the agent “actually does in the world” while the
second part chooses the policy t+1 = (pt+1) for the next
time step. We will also use the notation at = (at; t+1),
keeping in mind that only policies with names may be
chosen. This new policy is used in the next step to pick the
action at+1 = t+1(ae1:t). Note that only policies with names
can be chosen and that P = is not a possibility because it
entails a contradiction: j j = j(A E
2j j &gt; j j. A history can now be written as:
)jj(A E
) j &gt;
ae1:t = a1e1a2e2:::atet = a1 2e1a2 3e2:::at t+1et
The subscripts for policies are one time step ahead because
the policy chosen at time t is used to pick an action at time
t + 1. The subscript denotes at which time step the policy is
used. Policy t is used to choose the action at = (at; t+1).
No policy modification happens when at = (at; t).</p>
      <p>In the previous section, we used these rules to calculate
the probability of any finite history: P (et j ae&lt;tat) = (et j
ae&lt;tat) and P (at j ae&lt;t) = 1 if (ae&lt;t) = at and 0
otherwise. However, the second rule doesn’t take into
consideration that the agent’s policy is changing. Therefore, to
account for self modification, we need to modify the second
rule into “P (at j ae&lt;t) = 1 if t(ae&lt;t) = at and zero
otherwise”. To evaluate the V and Q-functions for self-modifying
agents, we need to use probabilities of complete histories
calculated in this way.</p>
      <p>Definition 2. Let ae1:t denote the history ae1:t with
information about self-modification removed so that ae1:t =
a1e1a2e2:::atet. A function f : (A E ) ! (anything)
0
is modification-independent if ae1:t = ae1:t implies that
f (ae1:t) = f (ae01:t).</p>
    </sec>
    <sec id="sec-5">
      <title>Modification-independence assumption: In the rest of</title>
      <p>the paper, we will assume that the agent’s belief and
utility function as well as the correct belief are
modificationindependent.</p>
      <p>4</p>
      <sec id="sec-5-1">
        <title>Definitions of bounded-rational agents</title>
        <p>
          We now extend the model from
          <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
          by
defining two types of bounded-rational agents which we will be
using throughout the paper: bounded-optimization agents
(described in Section 4.1) and bounded-knowledge agents
(described in Section 5.3). Bounded-knowledge agents can
be subdivided further into misaligned, ignorant and
impatient agents.
4.1
        </p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>Bounded-optimization agents</title>
      <p>We introduce the notion of -optimizers. Intuitively
speaking, the expected future discounted utility gained by an
optimizer is no more than lower than the optimal one in
any situation they could get into (that is, for any history).
Definition 3. We say that agent A is an -optimizer for
history ae&lt;t if it holds that</p>
      <p>Q(ae&lt;t (ae&lt;t))
sup Q(ae&lt;t 0(ae&lt;t))</p>
      <p>0</p>
      <p>When the utility function, belief and discount factor is
obvious from the context (or unimportant), we also speak of
policy being -optimizing (with respect to the utility
function and belief), meaning that the corresponding agent is an
-optimizer.
4.2</p>
    </sec>
    <sec id="sec-7">
      <title>Bounded-knowledge agents</title>
      <p>We consider agents with inaccurate knowledge of the correct
utility function (Definition 4), inaccurate knowledge of the
world (Definitions 5 and 6), and inaccurate knowledge of
the correct discount factor (how much future reward is worth
compared to reward in the present).</p>
      <p>Misaligned agents We define -misaligned agents as
agents whose utility function u has absolute error with
respect to the correct utility function u .</p>
      <p>Definition 4. We say that the instantaneous utility function
u has absolute error with respect to the correct utility
function u if</p>
      <p>sup ju(ae&lt;t)
t2N;ae&lt;t
u (ae&lt;t)j =
Ignorant agents We define -ignorant agents as agents
whose belief has error (absolute or relative depending on
the context) with respect to the correct belief .</p>
      <p>For belief, we define both relative and absolute error. This
is in contrast with utility, for which this does not make sense
in our setting. This is because when one speaks of relative
utility, one usually compares it to some default action of
“doing nothing” which we do not have.</p>
      <p>Bounded-rational agents
Definition 5. We say that a belief has absolute error with
respect to the correct belief if for any t 2 N, history ae&lt;t
and action a,</p>
      <p>k (ae&lt;ta) (ae&lt;ta)kT V (?)
where k kT V is the total variational distance.</p>
      <p>Recall that (on discrete measure spaces where all subsets
are measurable) for two distributions (formally two
probability measures) , on E , the total variational distance is
defined as
k kT V = sup j (E)</p>
      <p>E E
Definition 6. We say a belief
spect to the correct belief
ae&lt;t, action a, and percept e,
1</p>
      <p>(ejae&lt;ta)
1 +
(ejae&lt;ta)
1 +</p>
      <p>(E)j
has relative error with
reif for any t 2 N, any history
Impatient agents We define impatient agents as agents
whose discount factor is smaller than the correct discount
factor . This means they have a stronger preference for
immediate reward compared to the same reward in the
future.</p>
      <sec id="sec-7-1">
        <title>5 Exposition of the results</title>
        <p>We now formally describe our results, including statements
of the theorems. Proofs and description of the techniques
used to prove these results are included in the full version of
this paper.</p>
      </sec>
    </sec>
    <sec id="sec-8">
      <title>5.1 Performance of -optimizers can deteriorate</title>
      <p>
        In their paper,
        <xref ref-type="bibr" rid="ref9">Everitt et al. (2016)</xref>
        show that, for
modification-independent belief and utility function, if we
start with a perfect expected utility maximizer and at any
time replace the current policy by the initial policy, the
expected discounted utility stays the same. Therefore, later
policies cannot be worse than the initial policy and no
deterioration happens. We show that in the case of -optimizers,
such a replacement can never decrease the expected
discounted utility by more than (Inequality (2)) but can
increase it more, meaning that agent’s behaviour can
deteriorate with time (Inequality (1)). Specifically, it can
deteriorate at an exponential rate, until its actions become
arbitrarily bad – that is, until the expected future utility lost is the
maximum achievable utility (which is 1 1 ).
      </p>
      <p>Theorem 7. Let and u be modification-independent.
Consider a self-modifying agent which is an -optimizer for the
empty history. Then, for every t 1,</p>
      <p>Eae&lt;t [Q (ae&lt;t t (ae&lt;t))]</p>
      <p>Eae&lt;t [Q (ae&lt;t 1 (ae&lt;t))]
min( t 1 ; 1
1
)
(1)
where the expectation is with respect to ae&lt;t such that the
perceptions are distributed according to the belief and the
actions are given by ai = i (ae&lt;i).</p>
      <p>Moreover, for all histories ae&lt;t given by ai = i (ae&lt;i)
for which the agent is an -optimizer it holds that
Q (ae&lt;t 1 (ae&lt;t)) +</p>
      <p>Q (ae&lt;t t (ae&lt;t))
(2)
Equality in Inequality (1) can be achieved up to a factor of
at most .</p>
      <p>The expectation in inequality (1) is necessary as can be
demonstrated by the following example. Consider an
environment in which the first perception is with probability
(1 ) and otherwise. Regardless of the first perception,
the utility in the future is always 1 if the action following
this perception is a and 0 if b. An -optimizing agent which
performs action a may choose to self-modify to an agent
which performs action a after perception and b after
perception , thus losing 1 utility in the case of perception
, regardless of how small is.</p>
      <p>
        Setting = 0 allows us to easily recover Theorem 16 from
        <xref ref-type="bibr" rid="ref9">(Everitt et al. 2016)</xref>
        , showing that self-modifications do not
impact expected discounted utility gained by perfectly
rational agents. This proof is also considerably simpler than the
one in the original paper.
      </p>
      <p>If we only care about future discounted utility, this
deterioration in performance doesn’t need to concern us
because it only happens at future times when utility is heavily
discounted. From the definition of an -optimizer, the
maximum utility lost is indeed only . On the other hand, if we
care about long-term performance of the agent and have only
introduced the discount factor for instrumental reasons (as
would likely be the case), the possibility of self-modification
becomes a serious problem. The discount factor might be
introduced because optimizing the long-term future might be
computationally intractable.</p>
    </sec>
    <sec id="sec-9">
      <title>Bounded-knowledge agents are -optimizers</title>
      <p>In this section, we discuss perfect utility maximizers with
bounded knowledge and show performance guarantees for
such agents. In Section 5.3, we combine these results, show
how to relax the assumption of perfect optimization and,
most importantly, show how the performance of a
boundedrational agent differs between the cases with and without
self-modification.</p>
      <p>In Lemma 8, we show that if the agent’s estimate of the
expected discounted utility is at most away from the true
value, the agent will be a 2 -optimizer. In sections 5.2 to 5.2,
we show bounds on how inaccurate the agent’s estimate of
expected discounted utility can be, thus proving bounds on
optimization. In Section 5.2, we proceed differently: we
formulate the worst case as a solution of an optimization
problem which we then solve analytically.</p>
      <p>Lemma 8. Let A be a (possibly self-modifying) perfect
expected utility maximizer with knowledge = (u; ; ). Let
= (u ; ; ) be the correct knowledge. Assume that
jV (ae&lt;t)</p>
      <p>V (ae&lt;t)j
for all policies and histories ae&lt;t. Then, A is a 2 -optimizer
with respect to .
-misaligned agents are 0-optimizers We now consider
agents with an inaccurate utility function and derive bounds
on 0 such that the misaligned agent is an 0-optimizer.
Theorem 9. Let A be a perfect utility maximizer with
utility function u and error with respect to the correct utility
function u . Then it is a 12 -optimizer with respect to u .
Moreover, this bound is tight.</p>
      <p>In the random-error case when for any ae&lt;t, we
randomly choose u(ae&lt;t) from the set fmax(0; u (ae&lt;t)
); min(1; u (ae&lt;t) + )g, we give a simple lower bound that
is only a factor 4 away from the upper bound. Consider an
environment with only one perception 1 and actions f0; 1g
and u (1jae&lt;t0) = 1 2 and u (1jae&lt;t1) = 1. With
probability 1=4, it holds that u(1jae&lt;t1) = u(1jae&lt;t0), in which
case the agent may take the suboptimal action 0, thus losing
2 in instantaneous utility. At every step, it therefore loses
=2 instantaneous expected utility. In total, it then loses in
expectation 2(1 ) . We have thus proved the following:
Theorem 10. Let A be a perfect utility maximizer whose
utility function u is such that for any et; ae&lt;tat, the value
u(etjae&lt;tat) is chosen independently and uniformly from the
set fmax(0; u (etjae&lt;tat) ); min(1; u (etjae&lt;tat) + )g.
Then, the amount of utility lost is in expectation
2(1
)
-ignorant agents are 0-optimizers In this section, we
discuss agents with inaccurate belief. Theorem 11 gives
bounds on the utility lost as a result of the agent having an
inaccurate belief. We give an upper bound in terms of the
(weaker) absolute error and lower bounds in terms of both
absolute and relative error, showing that the upper bound is
tight up to factors of 2 and 4 for absolute and relative error.
Theorem 11. Let A be a perfect expected utility maximizer
whose belief has absolute error with respect to the
correct belief . Then it is a ( 1 2 1 (21 ) )-optimizer with
respect to and this bound is tight up to a factor of 2.
Moreover, if is the relative error, this bound is tight up to a
factor of 4.</p>
      <p>So far, we have considered the worst-case scenario. In
the next theorem, we show that in the case of both absolute
and relative error, the upper bound is tight up to a constant
factor even in the case when the error at each timestep is
randomly chosen from the set f ; g (that is, (etjae&lt;tat)
is chosen uniformly from the set fmax(0; (etjae&lt;tat)
); min(1; (etjae&lt;tat) + )g in the case of absolute error
and f (et1j+ae&lt;tat) ; min(1; (1 + ) (etjae&lt;tat))g in the case
of relative error), independently of other timesteps.
Theorem 12. Let A be a perfect expected utility
maximizer whose belief is such that for any et; ae&lt;tat,
the value (etjae&lt;tat) is independently for any argument
chosen uniformly from the set fmax(0; (etjae&lt;tat)
); min(1; (etjae&lt;tat) + )g in the case of absolute error
and f (et1j+ae&lt;tat) ; min(1; (1 + ) (etjae&lt;tat))g in the case
of relative error.</p>
      <p>Then, in expectation, the amount of expected discounted
utility lost is respectively
1
1</p>
      <p>=8)</p>
      <p>Impatient agents are -optimizers In this section, we
discuss the case when an agent has an incorrect discount factor
and give a bound on the performance of this agent with
respect to the correct discount factor. We only consider the
case when the agent discounts faster than the correct
discount rate – we deem this to be the interesting case as,
generally speaking, while optimizing in the long-term might be
desirable, it is difficult to achieve, so the agent is likely to
optimize in shorter term than desired. Bounds for the other
case can be derived by the same method. To simplify the
1 .
bounds, we define k = d lg e
Theorem 13. Let and be perfect expected utility
maximizers with respect to discount factors and
respectively for some , either with or without the ability to
self-modify. Let u, be their utility function and belief. Then
k 1
jV
(ae&lt;t)</p>
      <p>V
(ae&lt;t)j
k +
1
For ! 1, it holds that d lg1 e lg1 . This enables us to
simplify the previous result to get a good approximation for
when is close to 1:
k +
In this section we combine the results from sections 5.1
and 5.2 and present a bound on the utility lost by an agent
which is misaligned, ignorant, impatient and has bounded
optimization, all at the same time. It is an interesting feature
of this bound that the worst-case performance guarantee can
in some cases be improved by adjusting its discount rate.</p>
      <p>Recall that the functions f in the following theorem have
been defined in Section 1.1.</p>
      <p>Theorem 14. Let A be an o-optimizer for the empty history
with either (1) the ability to self-modify and
modificationindependent utility function and belief, or (2) without the
ability to self-modify and with a possibly
modificationdependent utility function and belief. Let be the agent’s
discount rate, u the error in its utility function wrt. the
correct utility function u and its absolute error in belief with
respect to the correct belief . Then at timestep t:
(1) If we let 0 be the smallest possible number such that A
at time t is an 0-optimizer, then Eae&lt;t [ 0] fopt( o; ) +
futil( u; ) + fbel( ; ) + fdisc( ; ) where the
expectation is over histories where perceptions are distributed
according to and actions are given by the agent’s policy.
Moreover, if o = 0, then 0 fopt( o; ) + futil( u; ) +
fbel( ; ) + fdisc( ; ) almost certainly.
(2) A will be an 0-optimizer, with respect to the correct
discount rate , where 0 o + futil( u; ) + fbel( ; ) +</p>
      <p>Moreover, when 1=2, there exists an agent which
achieves equality up to a factor of at most 8 and up to a
factor of 16 if is the relative error.</p>
      <p>6</p>
      <sec id="sec-9-1">
        <title>Future work</title>
        <p>We propose several directions for future research. In general,
it would be interesting to explore the central problem of
selfmodification safety under different agent and environment
models and with different assumptions.</p>
        <p>Bounded rationality models. We analyzed a model of
bounded-rationality with a strict upper bound on the size of
errors (of several kinds). While this shows that even agents
guaranteed to have small errors may self-modify in
detrimental ways, the analysis would be significantly different
for fully stochastic bounded rationality models (e.g.
negligible expected errors with non-negligible variance). One such
model of interest is Information-Theoretic Bounded
Rationality of Ortega et al. (2015).</p>
        <p>Awareness of own bounded-rationality. Whatever
underlying decision procedure the agent uses somehow
implicitly takes its -optimality into account – in particular since
the assumed -optimality depends on the behavior of future
agent versions. In our formulation, we do not assume the
agent to have explicit knowledge of its bounded rationality
model and , which would at least intuitively seem useful to
know.</p>
        <p>Note, however, that in our framing such explicit
knowledge would not be necessarily useful, as any deliberation
about it is subject to the same error within -optimality.
Therefore it may be interesting to explore bounded
rationality models where the information about own bounded
rationality could be explicitly reasoned about (with more
precision than e.g. modelling the trajectory of the full
environment). Would the agent then be more reluctant to
selfmodify?</p>
      </sec>
    </sec>
    <sec id="sec-10">
      <title>Time horizons and discounting. Avoiding temporal dis</title>
      <p>
        counting would likely yield results with stronger
implications (Section 2). We propose analysing the finite-time
undiscounted case, as well as exploring other means of
future value aggregation (finite or infinite, as explored by
        <xref ref-type="bibr" rid="ref3">Bostrom (2011)</xref>
        ).
      </p>
      <p>Model of self-modification. As noted above, embedded
agents with a strong influence on the environment may
self-modify by exploiting the environment. However, the
extent of this self-modification, and the strength and
stability of mechanisms against self-modification (e.g. via
modification-dependent utility function) require further
research.</p>
      <p>Probabilistic analysis. Build stochastic models of agent
rationality and self-modification, and perform full
probabilistic analysis. This may e.g. inform us about required
safety margins. In particular, approaches based on
statistical physics and information theory seems to be promising
here and have already proven fruitful in analyzing existing
optimization problems and algorithms.</p>
      <p>7</p>
      <sec id="sec-10-1">
        <title>Acknowledgements</title>
        <p>This work was carried out as part of the AI Safety Research
Program 2019. We are grateful to Vojteˇch Kovarˇ´ık, Jan
Kulveit, and Gavin Leech (in alphabetical order) for their
valuable inputs.</p>
        <p>Copyright © 2020 for this paper by its authors. Use
permitted under Creative Commons License Attribution 4.0
International (CC BY 4.0).
Miller, J. D.; Yampolskiy, R.; and Ha¨ggstro¨m, O. 2020. An
AGI Modifying Its Utility Function in Violation of the
Orthogonality Thesis. arXiv preprint arXiv:2003.00812 .
Russell, S. 2019. Human compatible: artificial intelligence
and the problem of control. New York, New York: Viking.
ISBN 9780525558613.</p>
        <p>Strotz, R. H. 1955. Myopia and inconsistency in dynamic
utility maximization. The review of economic studies 23(3):
165–180.</p>
      </sec>
    </sec>
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