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Our concerns fall into three areas: (1) Barsalou fails to make
clear what simulators are (vs. what they do); (2) activation of
perceptual areas of the brain during thought does not distinguish
between the activation's being constitutive of concepts or a mere
causal consequence (Barsalou needs the former); and (3) Barsalou's
attempt to explain how modal symbols handle abstraction fails.
Preparing words in speech production is normally a fast and
accurate process. We generate them two or three per second in fluent
conversation; and overtly naming a clear picture of an object can
easily be initiated within 600 msec after picture onset. The
underlying process, however, is exceedingly complex. The theory
reviewed in this target article analyzes this process as staged and
feedforward. After a first stage of conceptual preparation, word
generation proceeds through lexical selection, morphological and
phonological encoding, phonetic encoding, and articulation itself. In
addition, the speaker exerts some degree of output control, by
monitoring of self-produced internal and overt speech. The core
of the theory, ranging from lexical selection to the initiation of
phonetic encoding, is captured in a computational model, called
weaver++. Both the theory and the computational
model have been developed in interaction with reaction time
experiments, particularly in picture naming or related word production
paradigms, with the aim of accounting for the real-time processing in
normal word production. A comprehensive review of theory, model, and
experiments is presented. The model can handle some of the main
observations in the domain of speech errors (the major empirical
domain for most other theories of lexical access), and the theory
opens new ways of approaching the cerebral organization of speech
production by way of high-temporal-resolution imaging.
Females' tendency to place a high value on protecting
their own lives enhanced their reproductive success in the environment
of evolutionary adaptation because infant survival depended more upon
maternal than on paternal care and defence. The evolved mechanism
by which the costs of aggression (and other forms of risk taking) are
weighted more heavily for females may be a lower threshold for fear in
situations which pose a direct threat of bodily injury. Females'
concern with personal survival also has implications for sex
differences in dominance hierarchies because the risks associated
with hierarchy formation in nonbonded exogamous females are not
offset by increased reproductive success. Hence among females,
disputes do not carry implications for status with them as they do
among males, but are chiefly connected with the acquisition and
defence of scarce resources. Consequently, female competition is
more likely to take the form of indirect aggression or low-level
direct combat than among males. Under patriarchy, men have held
the power to propagate images and attributions which are favourable
to the continuance of their control. Women's aggression has
been viewed as a gender-incongruent aberration or dismissed as
evidence of irrationality. These cultural interpretations have
“enhanced” evolutionarily based sex differences by
a process of imposition which stigmatises the expression of aggression
by females and causes women to offer exculpatory (rather than
justificatory) accounts of their own aggression.
Although the study of visual perception has made more progress
in the past 40 years than any other area of cognitive science, there
remain major disagreements as to how closely vision is tied to
cognition. This target article sets out some of the arguments for both
sides (arguments from computer vision, neuroscience, psychophysics,
perceptual learning, and other areas of vision science) and
defends the position that an important part of visual perception,
corresponding to what some people have called early vision, is
prohibited from accessing relevant expectations, knowledge, and
utilities in determining the function it computes – in other
words, it is cognitively impenetrable. That part of vision is complex
and involves top-down interactions that are internal to the early
vision system. Its function is to provide a structured representation
of the 3-D surfaces of objects sufficient to serve as an index into
memory, with somewhat different outputs being made available to
other systems such as those dealing with motor control. The paper also
addresses certain conceptual and methodological issues raised by this
claim, such as whether signal detection theory and event-related
potentials can be used to assess cognitive penetration of
A distinction is made among several stages in visual processing,
including, in addition to the inflexible early-vision stage, a
pre-perceptual attention-allocation stage and a post-perceptual
evaluation, selection, and inference stage, which accesses long-term
memory. These two stages provide the primary ways in which cognition
can affect the outcome of visual perception. The paper discusses
arguments from computer vision and psychology showing that vision
is “intelligent” and involves elements of “problem
solving.” The cases of apparently intelligent interpretation
sometimes cited in support of this claim do not show cognitive
penetration; rather, they show that certain natural constraints on
interpretation, concerned primarily with optical and geometrical
properties of the world, have been compiled into the visual system.
The paper also examines a number of examples where instructions and
“hints” are alleged to affect what is seen. In each case
it is concluded that the evidence is more readily assimilated to the
view that when cognitive effects are found, they have a locus outside
early vision, in such processes as the allocation of focal attention
and the identification of the stimulus.
The relations among consciousness, brain, behavior, and scientific explanation are explored in the domain of color perception. Current scientific knowledge about color similarity, color composition, dimensional structure, unique colors, and color categories is used to assess Locke's “inverted spectrum argument” about the undetectability of color transformations. A symmetry analysis of color space shows that the literal interpretation of this argument – reversing the experience of a rainbow – would not work. Three other color-to-color transformations might work, however, depending on the relevance of certain color categories. The approach is then generalized to examine behavioral detection of arbitrary differences in color experiences, leading to the formulation of a principled distinction, called the “isomorphism constraint,” between what can and cannot be determined about the nature of color experience by objective behavioral means. Finally, the prospects for achieving a biologically based explanation of color experience below the level of isomorphism are considered in light of the limitations of behavioral methods. Within-subject designs using biological interventions hold the greatest promise for scientific progress on consciousness, but objective knowledge of another person's experience appears impossible. The implications of these arguments for functionalism are discussed.
Dienes & Perner (D&P) argue that nondeclarative
knowledge can take multiple forms. We provide empirical support
for this from two related lines of research about the development
of mathematical reasoning. We then describe how different forms
of procedural and declarative knowledge can be effectively modeled
in Anderson's act-r theory, contrasting this computational
approach with D&P's logical approach. The computational
approach suggests that the commonly observed developmental progression
from more implicit to more explicit knowledge can be viewed as
a consequence of accumulating and strengthening mental representations.
Cognitive impenetrability (CI) of a large part of visual
perception is taken for granted by those of us in the field of
computational vision who attempt to recover descriptions of space
using geometry and statistics as tools. These tools clearly point out,
however, that CI cannot extend to the level of structured descriptions
of object surfaces, as Pylyshyn suggests. The reason is that visual
space – the description of the world inside our heads –
is a nonEuclidean curved space. As a consequence, the only
alternative for a vision system is to develop several descriptions of
space–time; these are representations of reduced intricacy and
capture partial aspects of objective reality. As such, they make sense
in the context of a class of tasks/actions/plans/purposes, and thus
cannot be cognitively impenetrable.
The scenario used by Dienes & Perner to show that individual
representation can be implicit when property representation is explicit
can be adapted to show that property representation can be implicit when
individual representation is explicit. So there is no hierarchy of
explicitness, contrary to their claim. There is a reading of the
“implicit/explicit” distinction that does appear to exhibit
an asymmetry parallel to that alleged to hold between individual and
property. But this is not a distinction Dienes & Perner mention,
nor is it one that could be easily incorporated into their framework.
The qualitative and quantitative properties of color sensations and neuronal color coding are discussed in relation to physiological color exchanges and their evolutionary constraints. Based on the identity mind/matter thesis, additional physical measurements on color sensations are described that will allow us, at least in principle, to compare the qualitative properties of color sensations in different brains.
Campbell's analysis of the evolution of human sex
differences to include selection pressures on the female is generally
welcomed. This commentary raises some specific issues about the
evidence cited: the impact of paternal death on survival prospects; a
possible mechanism underlying a sex difference in fear; the selective
advantage of dominance hierarchies; and the absence of evidence that
testosterone causes human aggression.
Levelt et al.: Lexical access in speech production
Levelt et al. describe a model of speech production in which
lemma access is achieved via input from nondecompositional conceptual
representations. They claim that existing decompositional theories
are unable to account for lexical retrieval because of the so-called
hyperonym problem. However, existing decompositional models have
solved a formally equivalent problem.
Three major attempts by Barsalou to specify what makes a
perceptual symbol perceptual fail. One way to give such an account is to
use symbols' causal/nomic relation to what they represent, roughly
the way contemporary informational psychosemanticists develop their
theories, but this fails to draw the distinction Barsalou seems to have
A comprehensive theory of implicit and explicit knowledge
must explain phenomenal knowledge (e.g., knowledge regarding one's
affective and motivational states), as well as propositional
(i.e., “fact”-based) knowledge. Findings from several
research areas (i.e., the subliminal mere exposure effect, artificial
grammar learning, implicit and self-attributed dependency needs) are
used to illustrate the importance of both phenomenal and propositional
knowledge for a unified theory of implicit and explicit mental
This commentary discusses Pylyshyn's model of
perceptual processing in the light of the philosophical distinction
between the conceptual and the nonconceptual content of perception.
Pylyshyn's processing distinction maps onto an important
distinction in the phenomenology of visual perception.
It is worth considering whether particular behavioral measures from observers are ever consciously (or preattentively) transformed a priori so as to render inferences about them indistinguishable. This is unlikely, but recent experiments indicating color sensitivity and selectivity without visual awareness suggest that the distinction between what can and cannot be explained about color experience using behavioral responses may not be as obvious as Palmer concluded.
Levelt et al.: Lexical access in speech production
Though weaver has knowledge that gets activated
by words and pictures, it is incapable of responding appropriately to
these words and pictures as task demands are varied. This is because
it has a most severe case of attention deficit disorder. Indeed, it
has no attention at all. I discuss the very complex attention demands
of the tasks given to weaver.
Campbell's evolutionary explanation of women's
typically lower rates of interpersonal aggression is plausible, but
some supporting evidence requires scrutiny. Women may not commit less
interpersonal violence than men against small children. Women are more
vulnerable than men in same-sex encounters. The link between dominance
and reproductive success for males is less secure than was once
The perceptual symbol approach to knowledge representation
combines structured frames and dynamic imagery. The perceptual symbol
approach provides a good account of the representation of scientific
models, of some types of naive theories held by children and adults,
and of certain reconstructive memory phenomena. The ontological status
of perceptual symbols is unclear and this form of representation does
not succeed in accounting for all forms of human knowledge.
According to Pylyshyn, the early visual system is able to
categorize perceptual inputs into shape classes based on visual
similarity criteria; it is also suggested that written words may be
categorized within early vision. This speculation is contradicted by
the fact that visually unrelated exemplars of a given letter (e.g.,
a/A) or word (e.g., read/READ) map onto common
In Homo sapiens and other species, promiscuity,
risk-taking, and aggression are less matters of sex (having XX vs. XY)
than gender (giving PI vs. resources and/or genes). Classic role
reversals include: sea-horses, polyandrous birds, and a few heiresses
in England and Rome. Unlike other females, but like many males, they
are assertive, they take chances, and they are not chaste.