This poster outlines an Ecological Theory of Language Acquisition (ETLA). The theory views the early phases of the language acquisition process as an emergent consequence of the interaction between the infant and its linguistic environment. The newborn infant is considered to be linguistically and phonetically naïve but endowed with the ability to register a wide range of multi-sensory inputs along with the ability to detect similarity between the multi-sensory stimuli it is exposed to. The initial steps of the language acquisition process are explained as unintended and inevitable consequences of the infant’s multisensory interaction with the adult.
The theoretical model deriving from ETLA is tested using the experimental data presented in the two additional contributions from our research team (Gustavsson et al, “Integration of audiovisual information in 8-months-old infants”; Lacerda, Marklund et al. “On the linguistic implications of context-bound adult-infant interactions”). The generality of the ETLA’s concept is likely to be of significance for a wide range of scientific areas, like robotics, where a central issue concerns addressing general problems of how organisms or systems might develop the ability to tap on the structure of the information embedded in their operating environments

Gustavsson, Lisa

Klintfors, Eeva

Lacerda, Francisco

Lagerkvist, Lisa

Marklund, Ellen

Sundberg, Ulla

English

CogPrints Cognitive Sciences Eprint Archive

Ecological Theory of Language Acquisition

Cognitive Sciences ePrint Archive

Ecological Theory of Language Acquisition 
Francisco Lacerda*, Eeva Klintfors, Lisa Gustavsson, 
Lisa Lagerkvist, Ellen Marklund and Ulla Sundberg 
Department of Linguistics 
Stockholm University 
SE-106 91 Stockholm 
Sweden 
* frasse@ling.su.se
Abstract 
This poster outlines an Ecological Theory of 
Language Acquisition (ETLA). The theory views 
the early phases of the language acquisition 
process as an emergent consequence of the 
interaction between the infant and its linguistic 
environment. The newborn infant is considered to 
be linguistically and phonetically naïve but 
endowed with the ability to register a wide range of 
multi-sensory inputs along with the ability to detect 
similarity between the multi-sensory stimuli it is 
exposed to. The initial steps of the language 
acquisition process are explained as unintended 
and inevitable consequences of the infant’s multi-
sensory interaction with the adult. 
The theoretical model deriving from ETLA is 
tested using the experimental data presented in the 
two additional contributions from our research 
team (Gustavsson et al, “Integration of audio-
visual information in 8-months-old infants”; 
Lacerda, Marklund et al. “On the linguistic 
implications of context-bound adult-infant 
interactions”). The generality of the ETLA’s 
concept is likely to be of significance for a wide 
range of scientific areas, like robotics, where a 
central issue concerns addressing general problems 
of how organisms or systems might develop the 
ability to tap on the structure of the information 
embedded in their operating environments. 
1. Introduction 
Competent speakers of a language can explore the 
language’s combinatorial power to build up and define 
novel elements that can be recombined hierarchically to 
generate entities, to which a potentially endless recursive 
process can be applied to create new meanings. Indeed, 
even for finite recursions, the exponential growth 
associated with the combinatorial principle rapidly leads 
to such astronomically large numbers of possible 
sequences that the likelihood of random re-occurrence of 
a particular sequence becomes vanishingly small. But 
whereas this combinatorial power is good news for 
communication purposes, it clearly raises the issue of how 
a naïve language learner might be able to make sense of 
this immensely vast linguistic universe. Indeed, the 
famous argument on the “poverty of the stimulus” points 
out that the amount of information available from natural 
sentences is far too limited to allow the naïve language 
learner deriving the linguistic principles used in the 
ambient language, unless guided by an innate “language 
acquisition device” (LAD). 
However, in the ecological language acquisition 
setting the argument of the poverty of stimulus is much 
less relevant than it appears to be for adult-to-adult speech 
because the linguistic structure and the information 
content of the speech input typically directed to young 
infants is, in fact, rather stereotypical and repetitive 
(Lacerda, Marklund et al, 2004). The repetitive character 
of infant-directed speech and the ecological setting in 
which it occurs offer the grounds for the Ecological 
Theory of Language Acquisition (ETLA) that is presented 
in this communication. To be sure, the characteristics of 
the speech input directed to infants are likely to vary 
appreciably as a function of the infant’s age, but such 
changes reflect the adult’s continuous adaptation to the 
perceived linguistic development of the infant and fit well 
in the theoretical model as they complete the picture of 
the unfolding language acquisition process in its 
ecological settings. 
2. Theory outline 
The basic claim of the Ecological Theory of Language 
Acquisition is that early language acquisition is an 
emergent consequence of the multi-sensorial embodiment 
of the information available in ecological adult-infant 
interaction settings. According to ETLA, the basic 
linguistic referential function emerges from correlations 
between two (at least) of the sensory dimensions available 
in the speech interaction scene (Lacerda, 2003; Lacerda, 
Gustavsson, & Svärd, 2003). In spite of its simplicity and 
generality, it is argued that such a correlation mechanism 
is capable of initially capturing the relevant associations 
between the sounds of words and some of the sensory 
characteristics of their referents, given of the special 
characteristics of the speech input available to the infant 
and the ecological context in which infant-directed speech 
occurs. But in order to be able to pick up the referential 
link the infant must attend to the speech signal and indeed 
it is known that even newborns display a strong 
preference towards listening to speech, in particular the 
mother’s voice. Whereas this might be seen as a sign of 
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Proceedings of the Fourth International Workshop on Epigenetic Robotics
Lund University Cognitive Studies, 117, ISBN 91-974741-3-4
innate propensity for speech, the Ecological Theory of 
Language Acquisition attempts to frame the newborn’s 
preference for the spoken language as the result of a 
general recognition process that happens to link the 
infant’s pre- and post-natal auditory experiences. 
Indeed the newborn’s preference for speech can be 
explained as a consequence of perinatal continuity that 
does not involve specialized speech-oriented mechanisms. 
Because the fetus’ auditory system is functional by about 
150 days after gestation, the newborn’s preference for the 
speech signal may result from the infant’s recognition of 
familiar prosodic and rhythmic patterns from its pre-natal 
exposure to the speech produced by the pregnant woman. 
Thus, rather than being a specific interest for speech, as 
such, the newborn’s preference towards speech is seen as 
a consequence of a general recognition process that would 
apply to a very broad range of acoustic stimuli to which 
the infant might have been exposed to before birth. 
Undoubtedly, under typical circumstances, the speech 
signal is likely to induce particularly salient 
representations in the pre-natal infant as a consequence of 
the pregnant woman’s normal spoken interaction, but the 
crucial point here is that such a salience is not particularly 
related to the speech signal per se, but rather to its 
availability as a frequent acoustic signal during the last 
months of gravidity. Furthermore, because the speech 
signal available to the fetus is dominated by low 
frequencies due to the low-pass (LP) filter characteristics 
of the transmission over the amniotic liquid in which the 
fetus is immersed, it may be predicted that the newborn 
will tend to focus on the low-frequency aspects of the 
speech signal, mainly associated with prosodic and 
temporal aspects. (Nazzi, Bertoncini, & Mehler, 1998; 
Ramus, Hauser, Miller, Morris, & Mehler, 2000) 
After birth, the infant’s recognition of the prosodic 
patterns of speech fits nicely with the typically enhanced 
F0 modulations occurring in Infant-Directed Speech, as 
adults tend to reinforce the phonetic aspects of the speech 
signal that seem to be preferred by the infant. The 
newborn’s interest for the prosodic characteristics of the 
speech signal is likely to be an important initial 
component but, within the framework of the ETLA, it 
cannot account by itself for the infant’s subsequent 
language acquisition process. Thus, in the pursue of the 
mechanisms underlying the early language acquisition 
process, the characteristics of the speech input available to 
the young infant in its ecological context have to be 
considered and integrated with the infant’s perception and 
production capabilities. 
Although the prosodic characteristics of infant-
directed speech (IDS) are most likely engage the young 
infant’s attention (Fernald, 1989), the young infant is 
obviously also exposed to other types of speech that the 
infant can hear – like adult-directed speech, (ADS), adult 
speech directed to children (the infant’s older siblings, for 
example), child to infant, child to adult, etc., in the 
infant’s neighborhood. In fact, an extensive study of the 
language input available to a Dutch infant between six and 
nine months of age (van de Weijer, 1999) indicated that 
IDS, produced by an adult occurred on average for about 
14% of the speaking time that the infant was exposed to. 
Yet, during the period of IDS, the speech was produced 
with the infant at close range, which is likely to result in 
high salience for this type of speech. Considering that IDS 
is typically repetitive and refers to objects and situations 
in the infant’s immediate neighborhood (Lacerda, 
Marklund et al, 2004, this conference), the salience of the 
correlated auditory and visual information is likely to be 
high, providing an optimal ground for the emergence of 
the linguistic referential function. 
3. Modeling early language acquisition 
The principles of the Ecological Theory of Language 
Acquisition are being implemented in a mathematical 
model of early language acquisition that will be 
demonstrated in this communication. The model is based 
on multi-sensory unsupervised hierarchical pattern 
recognition and general memory processes. It operates on 
the particular type of input available to the infant in its 
ecological context. The model results will be tested 
against experimental data from language comprehension 
tests carried out with 8-month old infants (Gustavsson et 
al, 2004, this conference). 
The theory of language acquisition proposed in this 
communication has potential wide implications that go 
beyond the issue of language acquisition proper. Because 
it addresses the fundamentals of an emergent learning 
process, the theory may have significance for general 
problems concerning the discovery of hidden structure 
embedded broad classes of multi-dimensional input 
signals. 
Acknowledgements 
Research carried out with grants from the Swedish 
Research Council and the Bank of Sweden Tercentenary 
Foundation. 
Reference List 
Fernald, A. (1989). Intonation and communicative intent 
in mothers' speech to infants: is the melody the message? 
Child Dev., 60, 1497-1510. 
Lacerda, F. (2003). Phonology: An emergent consequence 
of memory constraints and sensory input. Reading and 
Writing: An Interdisciplinary Journal, 16, 41-59. 
Lacerda, F., Gustavsson, L., & Svärd, N. (2003). Implicit 
linguistic structure in connected speech. In (pp. 69-72). 
Umeå. 
Nazzi, T., Bertoncini, J., & Mehler, J. (1998). Language 
discrimination by newborns: toward an understanding of 
the role of rhythm. J.Exp.Psychol.Hum.Percept.Perform., 
24, 756-766. 
Ramus, F., Hauser, M. D., Miller, C., Morris, D., & 
Mehler, J. (2000). Language Discrimination by Human 
Newborns and by Cotton-Top Tamarin Monkeys. Science, 
288, 349-351. 
van de Weijer, J. (1999). Language Input for Word 
Discovery. MPI Series in Psycholinguistics. 
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