**ZELAZO – ARTICLE ON DEVELOPMENT OF CONSCIOUS CONTROL

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*ZELAZO development of self control

 

The development of conscious control

in childhood

Philip David Zelazo

Department of Psychology, University of Toronto, Toronto, ON, M5S 3G3, Canada

Developmental data suggest that the growth of executive

function in childhood can be understood in terms

of the development of consciousness. According to the

‘levels of consciousness’ (LOC) model, there are age related

increases in the highest degree of self-reflection

or LOC that children are able to muster in response to

situational demands. These increases in LOC with age

have consequences for the quality of experience, the

potential for recall, the complexity of children’s explicit

knowledge structures, and the possibility of the conscious

control of thought, emotion, and action. The

hierarchical LOCs identified by this analysis are also

useful for understanding the complex structure of conscious

experience in adults, and they provide a metric

for measuring the level at which consciousness is operating

in specific situations.

Like psychology generally, research on the development of

consciousness in childhood has a short history but a long

past. For early theorists such as Baldwin [1] and Vygotsky

[2], it was the central problem to be addressed by the new

science of psychology. But although there has been an

explosion of research on consciousness during the past

decade, very little of this research has been conducted from

a developmental perspective, and there is currently no

consensus concerning the characteristics of children’s

consciousness. Some theorists consider even infant consciousness

to be adult-like in most respects [3,4]. These

authors attribute to young infants not just sensory

consciousness of present sensations, but self consciousness,

consciousness of other minds, and the ability to act

deliberately in light of conscious representations. At the

other extreme are those who characterize infants essentially

as unconscious automata – capable of cognitive

function but lacking even sensory awareness [5-7].

Understanding children’s consciousness is important

in its own right, but developmental data also have

implications for consciousness in general. Whereas

some models based on adults distinguish between

consciousness and a meta-level of consciousness

(e.g. consciousness versus meta-consciousness [8], primary

consciousness versus higher-order consciousness [9],

core consciousness versus extended consciousness [10]),

it is often the case, as Schooler [8] notes, that these

two levels are conflated. For example, in the influential

information-processing models proposed by Schachter [11]

and Moscovitch [12], consciousness corresponds to a single

system, and information is either available to this system

or not. By contrast, developmental data argue for not

just two, but several dissociable levels of consciousness;

information can be available at one level but not at others.

The levels of consciousness (LOC) model [13-15] is a

developmental, information-processing model that describes

these hierarchically arranged LOCs and provides a metric

for measuring the level at which consciousness is operating

in specific situations. This metric should be useful in a

variety of investigations, not just in research on children’s

consciousness, because although most adults are capable

of high LOCs, the reflective processes that bring these

LOCs about are effortful and resource-demanding, and

adults often operate at relatively low LOCs (e.g. when tired).

Example of a knowledge-action dissociation illustrating

the need for different LOCs

Key aspects of this approach can be illustrated using a

simple example, which I will subsequently locate in the

context of a developmental theory. In the Dimensional

Change Card Sort, children are shown two target cards

(e.g. a blue rabbit and a red car) and asked to sort a series

of bivalent test cards (e.g. red rabbits and blue cars)

according to one dimension (e.g. color). Then, after sorting

several cards, children are told to stop playing the first

game and switch to another (e.g. shape, ‘Put the rabbits

here; put the boats there.’). Regardless of which dimension

is presented first, 3-year-olds typically continue to sort by

that dimension despite being told the new rules on every

trial (e.g. [16-20]; for review see [21]).

These children also show what Teuber [22] called a

‘curious dissociation between knowing and doing.’ That is,

they respond correctly to questions about the post-switch

rules even while perseverating on the pre-switch rules

[23]. For example, children who should be sorting by shape

(but persist in sorting by color) may be asked, ‘Where do

the rabbits go in the shape game? And where do the boats

go?’ Children usually answer these simple questions correctly

(but see [24]). Moments later, however, when told to

sort a test card (‘Okay, good, now play the shape game.

Where does this rabbit go?’), they persist in sorting by color.

On our account, 3-year-olds consciously represent the

post-switch rules at one LOC (which allows them to provide

verbal answers to the explicit knowledge questions),

and they consciously represent the pre-switch rules at that

same LOC (which allows them to keep the pre-switch rules

Corresponding author: Philip David Zelazo (zelazo@psych.utoronto.ca). in working memory to guide their sorting). However, they

12 Opinion TRENDS in Cognitive Sciences Vol.8 No.1 January 2004

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fail to reflect on their representations of the two rule pairs

at a higher LOC, which is why they cannot make a

deliberate decision to use the post-switch rules instead of

the pre-switch rules (which have now become associated

with the act of sorting). As a result, children’s knowledge of

the two rule pairs remains unintegrated (see Figure 1a),

and the particular rule pair that underlies their responses

is determined by relatively local considerations, such

as the way in which the question is asked. By contrast,

4-year-olds, like adults, seem to recognize immediately

that they know two ways of construing the stimuli. These

children spontaneously reflect on their multiple perspectives

on the situation, consider them at a higher LOC, and,

as captured by the Cognitive Complexity and Control

(CCC) theory [16,21], integrate them into a relatively

complex rule structure (Figure 1b). The close connection

between reflection and control is revealed in part by the

robust finding that performance on this task is correlated

with children’s ability to reflect on their own and others’

mental states [16,25,26].

The LOC model

As an information-processing model, theLOC model traces

the flow of information through a functional system,

illustrating the way in which primitive representations

(intentional objects) are processed at various LOCs as

they contribute to the complex hierarchical structure of

consciousness and come to control thought and action

(i.e. executive function). A central claim is that higher

LOCs are brought about by a type of reflection or re-entrant

processing that permits the contents of consciousness at

one level to be considered in relation to other contents at

that same level, resulting in a more complex conscious

experience. As a developmental model, the LOC model

shows how this functional system changes in the course of

ontogeny. Age-related increases in the highest LOC that

children can attain when attempting to solve a problem

are invoked to explain systematic age-related changes in

executive function [27].

Fundamental assumptions: minimal consciousness as

the first LOC

As James [28] noted, ‘Consciousness, however small, is

an illegitimate birth in any philosophy that starts without

it, and yet professes to explain all facts by continuous

evolution.’ Nonetheless, if one assumes that newborn

babies are conscious in some sense at birth, then it is

possible to account for subsequent changes. According to

the LOC model, newborn babies experience minimal

consciousness (minC) (cf. [29]), meant to be the

simplest, but still conceptually coherent, kind of consciousness

that accounts for the behavioral evidence. As

argued elsewhere [30], minC must be characterized by

intentionality in Brentano’s [31] sense (i.e. if one is

conscious in any sense then one must be conscious of

something), and it motivates approach and avoidance

behavior based on pleasure and pain. However, minC is

unreflective, present-oriented, and makes no reference to a

concept of self. So in minC, one is conscious of what one

sees (the object of experience), but not seeing what one

sees, let alone that one’s ‘self ‘ is seeing what one sees.

Subsequently, one cannot recall seeing what one saw.

In adults, minC underlies so-called implicit information

processing, as when we drive a car without full awareness

[29]. Even in the simplest case, where behavioral routines

are elicited directly and automatically, they are elicited as

a function of consciousness of something – say, immediate

environmental stimuli (cf. [32]). Implicit processing does

not occur in a zombie-like fashion; it is simply unreflective

and unavailable for subsequent recollection.

Consider how minC figures in the production of behavior

(see Figure 2). An actual object in the environment

(objA) triggers a ‘description’ from semantic long-term

memory. This particular description then becomes an

intentional object (or IobjA) of minC, which triggers an

associated action program in procedural long-term memory.

A rattle, for example, might be experienced by a minC

baby as ‘small thing’, and this description might trigger

the stereotypical motor schema of sucking.

Figure 1. (a) Unintegrated rule systems. Two incompatible pairs of rules (A vs. B

and C vs. D), corresponding to two different perspectives on the bivalent test

cards in the Dimensional Change Card Sort, are each represented at the same

LOC. Characteristic failures of executive function, such as perseveration and

knowledge-action dissociations, are likely to occur until these rule systems are

integrated into a single, more complex rule system. (b) An integrated rule system.

A degree of reflection is required to consider the two rule pairs in contradistinction

at a higher LOC. A higher LOC is required to formulate the higher order rule (E) for

deliberately selecting between rule pairs.

TRENDS in Cognitive Sciences

red blue

here there

rabbit boat

there here

red blue

here there

rabbit boat

there here

Color Shape

(A) (B)

(E)

(C) (D)

(A) (B) (C) (D)

(a)

(b)

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On this account, attribution of minC manages to explain

infant behavior until the end of the first year, when

numerous new abilities appear within months (i.e. infants

speak their first words, use objects in a functional way,

point proto-declaratively, and search flexibly for hidden

objects, among other milestones [33,34]). According to the

model, these changes can all be explained by the emergence

of the first new form of consciousness – recursive

consciousness (recC).

Recursive consciousness

The term ‘recursive’ is used here in the sense of a computer

program that refers to itself. In recC (Figure 2), the

contents of minC at one moment are combined with the

contents of minC at another via an identity relation (rel1),

allowing the toddler to label the initial object of minC. The

1-year-old toddler who says ‘dog’, for example, combines a

perceptual experience with a label from semantic longterm

memory, effectively indicating, ‘That [i.e. the object

of minC] is a dog.’ Similarly, on this account, pointing

indicates, ‘That is that.’ Notice that there must be two

things, the experience and the label, in order for one of

them, the experience interpreted in terms of the label, to

become an object of recC (see Box 1).

In the absence of a label, the contents of minC are

fleeting and unrecoverable; they are immediately replaced

by new intero- and exteroceptor stimulation. However,

because a label can be decoupled from the experience

labelled, the label provides an enduring trace of that

experience that can be deposited into both long-term

memory and working memory. The contents of working

memory (e.g. representations of hidden objects) can then

serve as goals to trigger action programs indirectly so the

toddler is not restricted to responses triggered directly by

minC of an immediately present stimulus. Now when objA

triggers IobjA and becomes the content of minC, instead

of triggering an associated action program directly, IobjA

is fed back into minC (called recC after one degree of

reflection) where it can be related to a label (descA) from

semantic long-term memory. This descA can then be

decoupled and deposited in working memory where it can

serve as a goal (G1) that triggers an action program even in

the absence of objA, and even if IobjA would otherwise

trigger a different action program (Figure 2). For example,

Figure 2. (a) A process model of minimal consciousness (minC). An object in the environment (objA) triggers an intentional representation of that object (IobjA) in semantic

long term memory (LTM); this IobjA, which is causally connected (cc) to a bracketed objA, becomes the content of minC, by way of which it triggers an associated action

program stored in procedural LTM, and a response is generated to objA. (b) Recursive consciousness (recC). The contents of minC are fed back into minC via a re-entrant

feedback process (curved red arrow), producing recC. The contents of recC can be related (rel1) to a corresponding description (descA) or label, which can then be

deposited into working memory (right) where it can serve as a goal (G1) to trigger an action program in a top-down fashion from procedural LTM.

TRENDS in Cognitive Sciences

descs descA rel1 <IobjA>

Iobjs IobjA cc <objA>

objA response

Iobjs IobjA cc <objA>

objA response

minC

minC

recC

(a)

(b)

Semantic LTM

Semantic LTM

Procedural LTM

action programs

Levels of consciousness Working memory

Procedural LTM

action programs

G1

items (e.g. goals)

14 Opinion TRENDS in Cognitive Sciences Vol.8 No.1 January 2004

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when presented with a telephone or an object hidden at a

new location, the recC toddler might put the telephone to

her ear (functional play) or search for a hidden object

without perseverating (as in Piaget’s famous A-not-B

task). The toddler responds mediately to the label in

working memory rather than immediately to an initial,

minC gloss of the situation.

The ascent of consciousness through subsequent levels

With each increase in LOC, the same basic processes are

recapitulated, but with different consequences at each

level. In general, however, as one ascends LOCs, which

correspond to minC with additional degrees of reflection,

one moves away from what Dewey [35] called the

‘exigencies of a situation’. Reflective processing is interposed

between a stimulus and a response, and this

permits the increasingly sophisticated selection and

amplification of certain determinants of behavior when

multiple determinants are present. It permits flexibility,

as opposed to perseveration; conscious control, as opposed

to stimulus control.

Self-consciousness

The next major developmental transition occurs at the end

of the second year – a transition so dramatic that Piaget

[36] called it the emergence of symbolic thought. More

recent accounts have tended to focus on implications for

children’s awareness of Self, emphasizing children’s first

use of personal pronouns, their self-recognition in mirrors,

and their display of self-conscious emotions such as shame

[37-39]. Consistent with these accounts, according to the

LOC model, this transition is brought about by another

LOC, referred to as self consciousness (selfC).

This LOC allows children to consider their own capabilities

vis-a’-vis a situation (i.e. to consider available

means as well as desired ends). Consideration of a means

relative to the goal that occasions it is a major advance that

allows children consciously to follow rules linking means

to ends [40]. As shown in Figure 3, children with selfC can

take as an object of consciousness a conditionally specified

self-description (SdescA) of their behavioral potential.

This SdescA can then be maintained in working memory

as a single rule (R1, including a condition, C, and an

action, A), considered against the background of a goal

(G1). Keeping a rule in working memory allows it to

constrain responses, regardless of fluctuating environmental

stimulation, which might pull for inappropriate

responses.

Reflective consciousness

In contrast to 2-year-olds, 3-year-olds exhibit behavior

that suggests an even higher LOC, reflective consciousness

1 (refC1). For example, they can systematically

employ a pair of arbitrary rules (e.g. things that make

noise versus are quiet) to sort pictures. According to the

model, 3-year-olds can reflect on a SdescA of a rule (R1)

and consider it in relation to another Sdesc (SdescB) of

another rule (R2). This relation (rel2) is a second-order

contrastive relation (as opposed to an identity relation).

Both of these rules can then be deposited into working

memory where they can be used contrastively to control

the elicitation of action programs. As a result, unlike

2-year-olds, 3-year-olds do not perseverate on a single rule

when provided with a pair of rules to use [40].

Of course, there are still limitations on 3-year-olds’

executive function, as seen in their perseveration in the

Dimensional Change Card Sort. This task requires the

integration of two incompatible pairs of rules into a single

structure, and this in turn requires children to adopt an

even higher LOC, reflective consciousness 2 (refC2), at

which the entire contents of refC1 can be considered in

relation to a Sdesc of comparable complexity. Evidence

indicates that this LOC first emerges by around 4 years of

age, together with a range of metacognitive skills studied

under the rubric of ‘theory of mind’ [16,25,26] (Box 2).

Notice that these LOCs are proportional to the degrees

of embedding illustrated in the tree structure in Figure 1

and captured by CCC theory. CCC theory shows how

changes in executive function can be explained by changes

in the maximum complexity of the rules children can

formulate and use when solving problems. The LOC model

shows how these changes in rule complexity are, in turn,

explained by increases in LOC. Together, CCC theory and

the LOC model provide a framework for understanding

executive function in terms of underlying processes, and

they illustrate why both executive function and reflective

processing might depend on the same neural systems

involving prefrontal cortex [41].

Box 1. Language and LOCs

Language has long been held to play an important role in consciousness

(e.g. [2,9,43,44]), and the LOC model follows in this

tradition. Language is required for recC and it plays a similar role at

higher LOCs, promoting increases in LOC (within age-related constraints

on the highest LOC). In particular, labeling one’s subjective

experiences helps make those experiences an object of consideration

at a higher LOC. Increases in LOC, in turn, allow for the flexible

selection of perspectives from which to reason. Therefore, for people

who are capable (in principle) of adopting a particular higher LOC,

labeling perspectives at the next level down will increase the likelihood

that they will adopt this higher LOC.

The effect of labeling on LOCs and flexibility can be illustrated by

work by Jacques, who developed the Flexible Item Selection Task

[45]. On each trial of the task, children are shown sets of three

items designed so that one pair matches on a certain dimension

(e.g. category of object), and a different pair matches on a different

dimension (e.g. size). A set of three items might therefore be a small

yellow teapot, a large yellow teapot, and a large yellow shoe).

Children are first told to select one pair (i.e. Selection 1), and then

asked to select a different pair (i.e. Selection 2). To respond correctly,

children must represent the pivot item (i.e. the large yellow teapot)

according to both dimensions. Four-year-olds generally perform

well on Selection 1 but poorly on Selection 2, indicating inflexibility

[45]. According to the LOC model, although 4-year-oldsmight not do

so spontaneously, they should be capable in principle of comprehending

two perspectives on a single item (as indicated, for example,

by successful performance on the Dimensional Change Card Sort

and a variety of measures of perspective-taking [27]). Therefore, the

model predicts that asking children to label their perspective on

Selection 1 (e.g. ‘Why do those two pictures go together?’) should

increase their tendency to adopt a different perspective on Selection 2,

which is exactly what Jacques found [46]. This was true whether

children provided the label themselves or whether the experimenter

generated it for them.

Opinion TRENDS in Cognitive Sciences Vol.8 No.1 January 2004 15

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Conclusion

According to the LOC model, there are four age-related

increases in the highest LOC that children can muster.

With each increase, reflection has important consequences

for the quality of subjective experience, the potential for

recall, the complexity of knowledge structures, and the

possibility of executive function. First, reflection adds

depth to subjective experience because more details can be

integrated into the experience before the contents of

consciousness are replaced by new environmental stimulation.

Second, each added degree of reflection (higher

LOC) causes information to be processed at a deeper, less

superficial level, which increases the likelihood of retrieval

[42]. Third, higher LOCs allow for the formulation and

use of more complex knowledge structures. Characteristic

errors of executive function, such as perseveration

and knowledge-action dissociations, are likely to

occur until incompatible pieces of knowledge are integrated

into a single, more complex structure via their

subordination to a higher-order rule, which is only possible

at a higher LOC.

Although formulated to explain developmental data,

this model suggests a framework for understanding the

vagaries of human consciousness across the life span,

and it makes predictions for future research. For example,

for each LOC in the model, it should be possible to

demonstrate conscious processing at that level but not

higher levels. These dissociations should be age-related

in childhood (and senescence) but should also occur in

adults in circumstances that demand effortful processing

(e.g. dual-task conditions, damage to prefrontal cortex).

In all cases, however, these dissociations should

have characteristic consequences for the control of

thought and action.

Box 2. HOTs and LOCs

Insofar as the LOC model emphasizes the importance of a secondorder

process for the experience of awareness at level recC, it

resembles a higher-order thought (HOT) theory of consciousness

[29,47]. However, it differs from these theories in crucial ways. HOT

theories claim that consciousness consists in a belief about one’s

psychological states (i.e. a psychological state is conscious when one

believes that one is in that state). By contrast, reflection is simply a

functional process that permits the contents of consciousness to

become an object of consciousness at a higher level, and it entails

no belief regarding psychological states. Indeed, according to the

model, a relatively high LOC (refC2, effected by several degrees of

reflection) is required for the formulation of beliefs about mental

states – often referred to as meta-representation or theory of mind

[48]. This suggestion is supported by the finding that children who

switch flexibly on the Dimensional Change Card Sort also tend to

pass tests indicating that they can reflect on their own (and others’)

mental states as such [16,25,26]. From our perspective, the suggestion

that meta-representation is required for conscious experience

[5] would seem to be a case of the psychologist’s fallacy – the

confusion of the psychologist’s own standpoint with that of the

psychological state in question. One need not have a concept of pain,

for example, to feel it [49].Adevelopmental perspective is instructive

in helping us to appreciate this point, which is supported empirically

by the presence of age-related dissociations between different LOCs.

Figure 3. Subsequent (higher) LOCs, including self consciousness (selfC), reflective consciousness 1 (refC1), and reflective consciousness 2 (refC2). The contents of each

LOC feed into the next level up, allowing increasingly elaborate representations and rules to be held in working memory.

TRENDS in Cognitive Sciences

Iobjs IobjA <objA>

recC

descA <IobjA>

selfC

Sdescs

refC1

refC2

SdescC <SdescB>

rel1

cc

rel2

rel2

rel2

SdescA <descA>

SdescB <SdescA>

objA response

Semantic LTM

descs

Levels of consciousness Working memory

ER1=PR1+PR2

goal; embedded rules

G1; PR1=R1+R2

goal; pair of rules

G1; R1=C1 A1

goal; rule=if c then act

G1

items (e.g. goals)

action programs

Procedural LTM

16 Opinion TRENDS in Cognitive Sciences Vol.8 No.1 January 2004

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Acknowledgements

Preparation of this article was supported by grants from the Natural

Sciences and Engineering Research Council (NSERC) of Canada and the

Canada Research Chairs Program.

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Letters to the Editor

Letters to the Editor concerning articles published in TICS are welcome. The letter will be sent to the authors of the original article to

allow them an opportunity to respond, and the letter and reply will be published together. Letters should be no longer than 400

words. Please note that submission does not guarantee publication and that the Editor reserves the right to edit letters for

publication. Please address letters to:

The Editor, Trends in Cognitive Sciences, 84 Theobald’s Road, London, UK WC1X 8RR

or e-mail: tics@current-trends.com

Opinion TRENDS in Cognitive Sciences Vol.8 No.1 January 2004 17

http://tics.trends.com

 

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