Proceedings of the 4th International Conference on Cognitive Science (Sydney, July 2003) pp.439-443

The easy and hard problems in cognitive science.
Ken Mogi (kenmogi@csl.sony.co.jp)
Sony Computer Science Labratories
Tokyo, Japan
http://www.qualia-manifesto.com

Abstract
Chalmers (1995) isolated the so-called "hard problem" of
consciousness from the "easy problems". His thesis did
the research community a great service by pointing out
correctly that the problem of consciousness cannot be
just swept away with a functionalist or connectionist
description. Here, citing some recent studies from
cognitive neuroscience, I argue that the easy and hard
problems are actually inseparable. A functionalist
description of a particular cognitive process is turned
into a hard problem the moment one starts to ask how theindividuality of the symbols used in the description isestablished. The marvel of the human cognition is notthat we are able to have a subjective experience as
separate from the functional operations in thesensorimotor domain, but rather that we are able toconduct functional operations while keeping the ability
to address and to be aware of the phenomenal and “hard”
aspects of subjective experience that accompany these
operations when necessary. Thus, perceiving qualities ofsubjective experience is a part of the human metacognitive abilities, and is related to such cognitive
capabilities as pretend play, theory of mind, andlanguage comprehension. I argue that such a viewpoint isessential in clarifying the often confusing arguments
surrounding the possibility of a computer simulation ofhuman cognitive process, which are based on a strict
distinction between what is computable and noncomputable. Specifically, I argue that cognitive
processes involving phenomenal qualities falls within thedomain of “FAPP” (for all practical purposes)
computability. I discuss how it is possible for a problem
to be in the “computable” or “functionalist” domain but
also “hard.

Introduction
The physical description of the world might seem toprovide a causally closed theory of how the things in
the world evolve, and the hope for someday attaining a“theory of everything” in this sense is still very much
alive (e.g. Taubes 1995). In fact, there is up to today no
grave demonstrated flaw in the physicalist’s program ofproviding a complete theory of the objective behaviorof materials in the world. The physicalist way oflooking at the world is equivalent to the computational
worldview, where every physical process in the world isa manifestation of some computational process. We canalternatively view the physical phenomena in the world

as obeying some physical laws described by a set of
equations or a result of some computational process, e.g.
in the form of cellular automata. In describing the
cognitive processes that occur in the brain, whilebasically assuming physicalism/computationalism, one
may add the functionalist’s point of view, the view thata description of the functionalities that the physically or
computationally implemented activities of neurons haveis a complete characterization of our cognitive process.
The golden triangle of physicalism, computationalism,
and functionalism seems to provide a complete
framework for describing everything under the sun,including our cognition. The difficulty in coming to asatisfactory explanation of the nature of the subjective
experience, however, is an entirely separate issue.
Chalmers (1995) pointed out that the nature of
subjective experiences is the only hard problem toexplain, whereas functional accounts of cognitive
processes, such as the ability to categorize, to direct
one’s attention to something, to remember the things
one experiences in a coherent way, whether consciousor unconscious, are easy problems. Chalmers correctly
pointed out that a conventional neurobiologicalapproach, even at their best, such as the one adapted by
Crick and Koch (1995), does not really address the hard
problem.
Here, while basically adapting Chalmer's viewpoint, I
present an alternative analysis of the problem.
Specifically, I argue that the so-called easy and hard
problems are actually inherently intertwined. The hard
problem cannot really be “solved” or “grasped” as longas we consider it as something separate from or outsideof the functionalist domain. In fact, the hard problem
and the functionalist agenda go hand in hand together.
As an example, one could take an easy approach or
hard one to the problem of the meaning of a word. A
philosopher can argue for many hours what the word
"time" means. When making an appointment with afriend, however, the same philosopher would advisedly
take an "easy" approach to the meaning of time,
adapting a functionalist's interpretation of such a phrase
as "let's meet at the station one hour later". If thephilosopher adapts a "hard" approach to the concept oftime, he is going to miss the appointment.
The same applies to the problem of qualia (Jackson
1982, Chalmers 1995, Mogi 1999b). One could take theorigin and nature of "redness of red" as a hard problem.

Proceedings of the 4th International Conference on Cognitive Science (Sydney, July 2003) pp.439-443

Indeed, how the qualia in our conscious experiencearise as a result of the neural activities in the brain is the
typical “hard problem”, one that cannot be handled withthe concept of “response selectivity” (Mogi 1999a), a
central dogma in neuropsychology for many years.
Despite that, one could equally treat the “redness ofred” within the framework of an easy problem, simply
pushing the button when one sees something red, when
instructed to do so.
Taking these examples at hand, if one examines how
the human cognitive processes occur, one is led to theconclusion that the easy and hard problems are not so
separate after all. The gist of the human cognitive
process is not that it is immersed entirely in the hard
problem, but that we can take alternatively hard or easy
approaches to our own cognition based on the“aspectual shape” (Searle 1992) relevant to the situation.
We are actually able to dynamically switch between
taking the phenomenal aspects of the conscious
experience at their face value and just treating it in thefunctionalist way. The ability of treating the sameprocess as easy and hand problems is actually the
essence of human cognition.

Metacognition
The human ability to treat the same problem (such as
the meaning of the concept “time” or the “redness” ofred) either as an easy or a hard problem is related to theability of metacognition, the ability to assess one’s own
mind state from a meta-level. When processing thecommand “press button when you see something red”,
one may not necessarily be aware of the “redness” ofthe object that has given the “go” signal. To be “aware”
of the sensory qualities of the percepts that support
one’s ability to perform a certain function is an instanceof metacognition, in that it is something that is added on
top of the rudimental functionality of performing theright thing at the right signal. When we are aware ofseeing something “red” in the visual field, we are ineffect having a metacoginition of our own internal state,making a phenomenological “measurement” of theneural activity in the brain at that psychologicalmoment.
In the above sense, metacognition is ubiquitous in our
subjective experience. Whenever we are aware of thesensory qualities (qualia) that make up the phenomenal
experience, we are having a kind of metacognition. In
that everything that we experience consciously has acertain phenomenal quality, consciousness is in its mostgeneral sense a metacognition of one’s internal state interms of qualia. To regard a particular cognitive process
as a hard problem is then dependent upon having ametacognition of phenomenal qualities accompanying
the cognitive process in question. The easy approach tocognitive function is one without the metacognitiveelement.
In order to grasp the relation between having thecapability of metacognition (and therefore being awareof having qualia in one’s conscious experience) and theconventional functionalist description of cognitive
processes, it is necessary to realize that metacognition isprobably not a solely human phenomenon.
The ability of metacognition is likely to have emerged
gradually in the history of evolution. Rhesus monkeys
are able to monitor how certain one is about a memorytask that one is about to perform (Hampton 2001).
When given an option to avoid the task, the probabilityof the monkey to avoid the task appears to increase as
the probability of correct answer decreases. Thus, themonkey seems to be able to assess its internal state,monitoring how certain it is about the memory task.
Being able to explicitly reflect on one’s own internal
state is not likely to be highly developed in lower
animals. However, the rudimentary ability to be awareof the visual qualia in one’s visual field, in itself ametacognitive process in that it adds something on topof the purely functional description of the visual
process, is likely to have emerged before the advent of
more advanced abilities to assess one’s internal state
within the ultimately linguistic intentional framework.
The binding of sensory features, in particular that of“property binding” (Treisman 1996) apparently occurs
in terms of the various visual qualia involved (color,surface texture, transparency, motion, etc) beingorganized into a particular locus in the visual field. The
fact that the ability to perceive the environment in termsof bound features is ubiquitous from lower animals is
consistent with the assumption that the ability to have ametacognition of phenomenal sensory qualities has
occurred early in evolution.
By the very nature of conscious subjective experience(we cannot in principle certify if other humans are infact “zombies” (Chalmers 1996) or not), it is not clear if
the rhesus monkey has the same kind of conscious
experience associated with metacognition in humans.
We do not know what it is like be a bat (Nagel 1974),
but that should not in itself exclude the possibility thatbats have metacognitive abilities. The difficulty ofassigning metacognition to animals comes from the factthat at present it is not clear what essential new element
having a metacognition of something adds on top of theconventional functionalist paradigm of the cognitive
process.

Language and metacognition
It is illuminating here to consider the role themetacognition of the semantics of language plays in ourdaily conversation.

Proceedings of the 4th International Conference on Cognitive Science (Sydney, July 2003) pp.439-443

Metacognition is a particularly central and important
issue when it comes to the semantics of language. It isdifficult to pin down the meaning of any single wordwhen you come to full grips with the semantic richnessof the language. For example, the usage of the word“light” in the English language cannot be simply
grasped by stating that the word “light” is a shorthandfor the electromagnetic wave that one gets as a solution
for the Maxwell’s equation. Phrases like “she is thelight in my life” certainly demonstrates the almost
infinite nuances in which this particular word can be
employed. The definition of the meaning of andaccounting for the ultimate origin of a single word is as
hard a problem as one can get in cognitive science. In
this sense, the metacognition of a meaning of a word isnever complete.
However, in daily life we use the words as if we
understood their meaning. Taking a behaviorist’s
standpoint, understanding the meaning of words might
be taken to imply that one acts as if one understands themeaning of the word, a philosophically practical
viewpoint taken by the classic paper by Turing (1950).
To understand language in a broader context ofcognitive processes, one would probably have to extend
the linguistic behaviorism introduced by Turing to akind of “neural behaviorism”. The ability to understanda particular system of language is to be found in thecortical circuit of handling semantically rich intentional
aspects of percepts, and does not necessarily have to be
expressed explicitly as a verbal output. One does nothave to be able to utter a single word to behave as if one
understood the meaning of a word in a simple sense.
Even pre-linguistic children, when tested by theparadigm of preferential looking, can exhibit behavior
as if they understood the meaning of a word. For
example, if the children are presented with a pair of
pictures, one of which is a picture of an apple in various
forms and the other is picture of other objects, inconjunction with the auditory stimulus of “apple”, they
preferentially look at a the picture of an apple longer
than at the other one (Sudo and Mogi 2003).
Needless to say, the infants are not likely to have ametacognitive ability to consciously reflect on themeaning of a word. The development of the fluency oflanguage and the ability to verbally improvise seems tocoincide with the ability to reflect in a metacognitive
sense on the meaning of a word, if necessary.
Taking the Turing test paradigm and the idea of auniversal Turing machine that emulates human
linguistic abilities at the face value, it is not at firstglance apparent how the metacognitive process or theability of addressing the hard problem helps in passing
the Turing test or implementing computational abilities
in a universal Turing machine.

The Computability of Cognitive processes
Faced with the apparent hard problems concerning the
subjective experience, and the difficulty of grounding
the phenomenal aspects of cognition on a computationalor functionalist basis, some authors have referred toconcepts that are generally considered to be outside thereach of physical/functional framework that is usuallyassumed in describing the cognitive processes in thebrain as a possible remedy to the problem.
One idea that has been occasionally cited as a sourceof remedy to the hard problem is that of computability.
Penrose (1989) claimed that an essential ingredient of
human conscious cognitive process, i.e. understanding,is something that falls outside what is computable,
citing the incompleteness theorem of Goedel (1931).
Penrose also claimed that the non-computable aspectsof human cognition could be only understood within theframework of a theory of quantum gravity, which will
be presumably formulated in a non-computable
framework.
As Penrose admits, at present it is difficult to come toan actual description of a non-computable process, all
the more so to give a description of physiologicalrealistic non-computable process that actually goes onin the brain. One example of non-computable processthat Penrose gives involves the judgment of the halting
or otherwise of a particular Turing machine. But it isdifficult to envision how such a process could be
implemented in the brain.
Regardless of the practical implementability of a noncomputable process, it is certainly interesting andlegitimate to ask whether conscious cognitive processes
falls within the computable class. In particular, it isinteresting to ask whether aspects of the hard problem
such as qualia or the semantics of words, and our
metacognitive ability to reflect on those phenomenal
properties, fall within what is computable.

FAPP computability
Here, it is helpful to introduce the concept of “for allpractical purposes” (FAPP). The term “for all practical
purposes” was coined to provide an excuse for the
standard interpretation (i.e., the Copenhagen
interpretation) of the wave function reduction process inquantum mechanics (e.g. Bell 1989). There are both
epistemological and ontological difficulties concernedwith the wave-particle duality and wave function
reduction in the Copenhagen interpretation of quantum
mechanics, illustrated by the famous paradox ofSchrodinger’s cat. However, for all practical purposes,i.e., in terms of giving an accurate prediction for the
behavior of particles within the limits of knowability set

Proceedings of the 4th International Conference on Cognitive Science (Sydney, July 2003) pp.439-443

by the general principles of quantum mechanics, theCopenhagen interpretation seems to work without any
practical flaw. The Copenhagen version of quantum
mechanics is a complete theory FAPP, although gravely
unsatisfactory from the point of view of
epistemologically complete description of the world.
There’s an analogy between the point of view that the
Copenhagen version of quantum mechanics is complete
and the idea that it is possible to simulate all objective
aspects of human cognitive processes by computational
means. One could extend behaviorism to neural
behaviorism, and claim that the objective behavior ofneurons, whether it is explicitly reflected on external
bodily movements or not, gives a complete descriptionof human cognitive process. Given the universality ofTuring machines, in addiction to the general freedom
involved in establishing a mapping between the
behavior of physical systems (even those as complex as
the human brain), it is difficult to envisage an instanceof knowably non-computable process that isrepresentative of human cognition. Our intuition thatthe phenomenal aspects of our cognition cannot be
explained by any computational models is a strong one.
Therein lies the ultimate source of inspiration forarguments like the one by Penrose. However, it isdifficult to envisage an aspect of the cognitive processthat is knowably non-computational.
In the rigorous mathematical sense, the difference
between what is computable and what is not is a clear
one. On the other hand, in considering the mapping
between numerical reality and the physical reality, it is
not always apparent if the watershed between what iscomputable and what is not is relevant in physicalreality. One cannot compute an irrational number bymeans of a finite process in a Turing machine withfinite number of states. When irrational numbers are
non-computable in a system, and only rational numbers
can be computed, whether a state is to be represented bya rational or irrational number makes a huge differencein mathematical reality. However, in real physicalsituations, it is not apparent whether the distinction
between a rational and irrational number is relevant or
not. One can find infinitesimally close rational number(which one can compute) given any irrational number(which one may not be able to compute). In mapping
the real physical processes (on which the conscious
cognitive process ultimately supervene) to numbers, thedifference between a rational number and irrational
number does not appear to make any practicaldifference.
In a deep philosophical sense, it is not apparent how
numbers are materialized in the physical process in theworld. The relevance of computability is heavily
dependent on the relation between the numerical andthe physical. In arguing about computability, thedifference between rational and irrational numbers

makes a whole world of difference. In the real world,
we are very much hard pressed to find any processcognitive or otherwise which critically hinges upon adistinction between what is computable and what is not.
For all practical purposes, therefore, it seems
reasonable to assume that all cognitive processes,
whether conscious or unconscious, are computable. The
FAPP computability of cognitive processes, including
those conscious processes involving qualia and selfconsciousness, has important implications for the natureof conscious experience, and its relation to such
conventional viewpoints as functionalism andconnectionism.

Consciousness and functionalism
If we embrace the FAPP computability of conscious
process, the arguments on consciousness dependent on
the hypothesized non-computability of conscious
process become irrelevant.
The Weltanschauung that needs to be taken, then, is
one where the phenomenological and functionalist
descriptions of the cognitive processes are intertwined.
The phenomenal aspect of subjective experience is not
something that is beyond or outside functionalism, butsomething that goes with it.
When we reflect on the way that the human cognitive
processes are actually organized, we discover that what
is on the surface within the domain of functionalism istightly coupled with the phenomenal properties ofpercepts, especially when metacognition is involved.
When performing a simple numerical manipulationsuch as Euclid’s algorithm, we may appear to be
performing a purely computational task. When
metacognition of the sensory qualities (qualia) of thepercepts involved in the apparently computational
process is taken into consideration, however, we
discover that qualia are involved in, and underlie, thecomputational operations as they are perceived in our
subjective experience. The easy and hard aspects of ourcognitive processes are thus tightly intertwined, while
everything can be grasped in the FAPP computable
domain as far as the objective behavior is concerned.
The significance of the human cognitive abilities toswitch between the easy and hard stances is clear insuch cases as pretend play and theory of mind (BaronCohen et al. 1985). It is in general a hard problem to beable to pretend to be somebody else, or to come to anunderstanding of other’s mind. Taking an “easy”
approach, one may perform cognitive tasks startingfrom a simple assumption, e.g. in such cases as a boy
pretending to be a girl or guessing what caused thesadness of one’s friend based on external observationand knowledge. One may even claim that some aspectsof the pretend play and theory of mind can be
implemented as an algorithm. On the other hand, when

Proceedings of the 4th International Conference on Cognitive Science (Sydney, July 2003) pp.439-443

coming to terms to the phenomenal aspects of actual
subjective experience of being a girl or one’s sad friend,
hard aspects of the problem suddenly emerge. In ourdaily cognitive activities, we basically perform the tasks
adapting the easy stance, while reflecting on themetacognitive aspects that eventually lead to the hard
problem when relevant. The fact that the human being
can lead a highly social life is very much dependent on
the ability to treat the potentially hard problem ofpretending and guessing other’s mind as an easy
problem, while maintaining the metacognitive ability to
immerse oneself in the hard problem when necessary.

Conclusions
Nobody can deny that conscious experience exists.
I once had an argument with a colleague of mine in
University of Cambridge, U.K., when he claimed that
there is no such a thing as consciousness. When I faced
him with the question “but surely you admit that there
is a clear difference in your subjective experience
between when you are awake and when you are
sleeping”, he claimed that as far as he was concerned,
there was no essential subjective difference between theawake state and the sleeping state (Pelah, 1997). I am
still hard pressed to come to a reasonable interpretationof his remark, although it was certainly a consistent one
from somebody who denied the existence of
consciousness.
The idea that the functional or computationaldescription of the neural processes in the brain is allthat is required is epistemologically unsatisfactory but
probably FAPP true. The great difficulty experienced
by those trying to go beyond the functionalist kingdom
is probably due to the fact that people have been
looking at the wrong places.
The reality of the human cognitive processes is that theeasy and hard problems are inseparable. Our ability toswitch between the easy and hard stance is thefoundation for the flexible adaptation to the natural andsocial environment. The solution for the admittedly
difficult problem of accounting for the phenomenal
qualities of our subjective experience is to be sought inthedelicatemannerinwhich
thephysicalist/computationalist/functionalist
description
can go hand in hand in our cognition. The neuralmechanism underlying metacognition, in the broadest
sense of the term including awareness of sensory qualia,
would provide the essential springboard for theunderstanding of consciousness.

Acknowledgments
I thank my colleagues Takashi Ikegami and Yukio
Gunji for helpful discussions concerning the issues
addressed in this paper.

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