PSYCOLOQUY V2 #8 (2.8.4 Paper: Connectionism/Reading/Skoyles: 288 l)
Stevan Harnad
harnad at clarity.princeton.edu
Wed Sep 25 11:43:38 EDT 1991
----------------------------------------------------------------------
From: ucjtprs at ucl.ac.uk
Subject: 2.8.4 Paper:Connectionism, Reading and the Limits of Cognition/Skoyles
Rationale for Inviting PSYCOLOQUY Commentary:
(a) The literature on reading acquisition is becoming fragmented: Here
is a theory which can bring together the modellers and those collecting
data.
(b) I was brought up upon Thomas Kuhn, so the first things I look for
are anomalies. I think I found two. What better way to bring them to
other people's attention than to show that they are different aspects
of the same phenomena?
(c) Many literate but phonologically disabled readers exist who were
delayed, often to the point of failure, in learning to read. Yet they
eventually learn to read, though often only in their teens. This
suggests that the processes underlying their reading competence are
functionally intact but that something related to their phonological
handicap stops their normal development. At present that link between
phonological disability and reading failure is only understood in terms
of a correlation. By proposing a mechanism I hope to persuade other
researchers if not to adopt my theory then propose other causal
mechanisms. This is important: Only with causal theories can
scientifically based interventions to ameliorate dyslexia develop.
Here are some issues and related questions which might be addressed in
the PSYCOLOQUY Commentary. (Note the length of my own comments does not
indicate importance.)
(1) The nature of connectionist training: Much has been written about
the training rules used to adjust networks )back-propagation, etc., and
effects of the numbers of hidden units). Little (actually I can find
none) has been written about the provision of error-correction
feedback.
Some questions: What happens if error-correction feedback is degraded
-- if it is only sometimes correct: How does this affect learning?
What happens if this feedback is delayed (one reason why it may be
degraded) or its acquisition interferes with the other processes
involved in network training? These questions are important because
networks learn and function in the real world where error correction
feedback may not be synchronised with network training. Or feedback may
only be obtainable by sacrificing the efficiency of other processes,
including those training the network.
(2) Humphries and Evett in a target article in Behavioral and Brain
Sciences argued that adult reading was nonphonetic. That was in 1985.
Are they and their commentators of the same opinion now as then?
(3) What is phonetic reading? It used to be defined in terms of a
person's ability to read nonwords. How could nonwords be read except by
sequential grapheme-phoneme translation? Connectionism shows that
nonword reading can be done purely by processes trained on real words
without the use of special grapheme-phoneme translation processes. I
defined phonetic reading in terms of word recognition processes which
depend for their recognition of words in some way upon a reader's oral
vocabulary. Some commentators may want to challenge this.
(4) Phonology and success at reading is a greatly debated subject. I
have left the exact nature of phonetic reading unstated -- partly
because I believe that the mechanisms involved may vary over time and
between individuals (although all share a common dependence upon access
to oral vocabulary). This may be controversial, however.
(5) Dyslexic and phonology -- there is a link, but its nature is still
unresolved. Some commentators might want to question this link (e.g.,
Bruno Breitmeyer and William Lovegrove).
(6) Reading research has had little effect on educators. There is the
"whole word method" movement, which does not ascribe any importance to
phonology. Representatives of various educational methods might want to
give their views.
(7) Cognitive development rarely discusses the role of error-correction
feedback upon cognitive development (although it would hardly be an
original idea to suggest it is important). In reading development we
have an example of how important it is. I suggest it is not unique.
Commentators might wish to suggest other examples (both involving
endogenous and external sources of feedback).
(8) Dyslexics might like to contribute. I am (or rather was) dyslexic.
I would be interested to contact other dyslexic psychologists.
Connectionism, Reading and the Limits of Cognition
John R. Skoyles,
Department of Psychology,
University College London,
London WC1E 6BT, UK.
Abstract
You read these written words without using your knowledge of how they
sound. A children's ability to do this predicts their success in
learning to read. Connectionist (PDP) models of cognitive processes
using networks can explain why this is so. Connectionism successfully
simulates "nonphonetic" reading skills. Networks, however, learn by
error-correction feedback -- but where does the learner-reader get this
feedback? I suggest that it is from the phonetic identification of
words. This conjecture might help explain (1) the pattern of reading
development in children and (2) dyslexia as well as (3) raising
questions for research aimed at making learning to read easier. In
addition, I suggest that error-correction feedback may have an
important and general role as a "bottle-neck" in the development of
cognition.
Keywords: dyslexia, connectionism, development, error correction, reading.
How did you learn to read these words? Recent reading research has
thrown up two anomalies in the acquisition of word learning. I propose
a theory which links them. It provides a new way of looking at the
development of reading and cognition.
Anomaly 1: You read these words nonphonetically, that is, you
identify them without using your oral knowledge of how words sound
(Humphrey and Evett, 1985). But the best predictors of children's
success in learning to read are language related skills such as initial
phonetic awareness (Stanovitch, Cunningham, & Feeman, 1984) and
phonetic instruction (Bradley and Bryant, 1983) - skills which are
needed for phonetic reading. Why should skills needed for phonetic
reading predict later success in nonphonetic reading?
Anomaly 2: Connectionist (PDP) neural network simulations of reading
successfully explain many experimental facts found about word
recognition (Seidenberg & McClelland, 1989). Like adult reading, these
simulations are nonphonetic -- they lack any connection with our oral
knowledge about how words sound. But there is a problem with their
success: although they are advocated as models of word learning, they
can, paradoxically, only learn to recognise words if the word learner
can already read.
The problem originates in the need for networks to be tutored with
error correction feedback. Reading networks learn by having their inner
nodes adjusted after the network has read a word. This adjustment (also
called training) depends upon whether the network has read a word
correctly or not: The network's nodes are adjusted differently
depending on whether or not it correctly identifies a word. This error
correction, however, puts an element of circularity at the heart of
network word learning, for it makes successful word learning depend on
the learner's already being a good reader (otherwise the processes
training the network cannot know whether or not the network has read a
word correctly).
This condition in which successful word learning depends on
pre-existing reading does correctly describe learning readers, however
-- the children who learn to read most easily are those who are good
readers already -- if we appreciate that the phonetic identification of
words is a form of reading. The first anomaly raises the question of
why phonetic reading predicts success in nonphonetic reading. The
second anomaly answers it: I conjecture that initial phonetic reading
skills are needed to train nonphonetic skills. The better their
phonetic skills, the easier learning readers find it to provide error
correction feedback (by recognising words phonetically). They are
accordingly in a better position to train their developing reading
networks and thereby learn to read nonphonetically.
I suggest that reading development is a double process, involving a
trade off between the different advantages and disadvantages of
phonetic reading and nonphonetic reading. The underlying story, I
propose, is this: The phonetic identification of words is inefficient
for normal reading, both in terms of speed and its use of mental
attention (because it depends upon the use of oral vocabulary). In
contrast, the nonphonetic recognition of words is suited for the
demands of reading as it is quick and undemanding cognitively (an
important requirement if the mind is to focus upon what it has read
rather than recognising words). However, nonphonetic reading is
difficult to acquire because it needs to be trained with error correction
feedback. The reading development overcomes this limitation by the use
of the less efficient phonetic identification of words to provide this
feedback; afterwards, the phonetic identification of words is dispensed
with.
This suggestion explains other facets of the acquisition of reading
skills. It fits the pattern of normal child reading development:
Children go through a period of phonetic reading before progressing to
nonphonetic reading (Frith, 1985). I suggest that this is due to the
advantage mentioned above for the development of nonphonetic reading
derived from prior skills in recognising words phonetically.
This suggestion may also explain the link between difficulties in
recognising words phonetically and dyslexia (Snowling, 1987). The
majority of dyslexics have impaired phonological skills (particularly,
but not exclusively, phonologically segmenting words), but they seem to
have intact nonphonological processes. Indeed, given time, some of them
(Campbell & Butterworth, 1985) persevere at learning words and become
normal readers -- presumably because they use less efficient means than
phonology to training their nonphonetic reading abilities.
The notion that phonology may play a role in word learning is not new
(e.g., see Jorm and Share, 1983). What is novel, however, is the link
between phonology and the network training. This is unexpected. It also
allows some important questions to be raised. There must be an optimal
time window for error correction to aid network training. How long is
this? There must also be a limit on how cognitively demanding obtaining
error correction feedback can be before it interferes with training and
the reading process, but how demanding? It may be that the importance
of phonetic reading is not just that it provides error correction
feedback but that it provides this information effectively and
nondisruptively when word training processes need it. If these
questions can be answered then this may help in the development of better
methods for helping people with word learning problems.
This model of word learning has wider importance. Word learning in
reading may not be unique. Error correction feedback -- the need for
learners to know whether or not they have performed the skill they are
learning correctly -- may be a general bottle-neck limiting cognitive
growth. No one has looked at cognitive development from this
perspective, so its importance is largely unknown, but it could
explain why cognitive development tends to go in stages: Spurts of
cognitive growth could be due to the development of new strategies and
means for overcoming problems in obtaining this information.
References.
Bradley, L., & Bryant, P. E. (1983). Categorisation of sounds
and learning to read: A causal connection. Nature 301:
419-421.
Campbell, R. & Butterworth, B. (1985). Phonological dyslexia
and dysgraphia in a highly literate subject: A
development case with associated deficits of phonemic
processing and awareness, Quarterly Journal of Experiment
Psychology 37A: 435 - 475.
Frith, U. (1985). Beneath the surface of developmental
dyslexia. In K. E. Patterson, J. C. Marshall, & M.
Coltheart (Eds.), Surface dyslexia. London: Routledge and
Kegan Paul.
Humphries, G. W., & Evett, L. L. (1985). Are there independent
lexical and nonlexical routes in word processing? An
evaluation of the dual-route model of reading. Behavioral
and Brain Sciences 8: 689-740.
Joam, A. F. & Share, D. L. (1983). Phonological recoding and
reading acquisition. Applied Psycholinguistics 4: 103-
147.
Seidenberg, M. S. and McClelland, J. I. (1989). A distributed,
developmental model of word recognition and naming.
Psychological Review 96: 523-568.
Skoyles, J. R. (1988). Training the brain using neural-network
models. Nature 333: 401.
Snowling, M. (1987). Dyslexia: A cognitive developmental
perspective. Oxford: Basil Blackwell.
Stanovitch, K. E., Cunningham, A. F., & Feeman, D. J. (1984).
Intelligence, cognitive skills and early reading
progress. Reading Research Quarterly 19: 278-303.
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