Gary Lupyan
http://www.cnbc.cmu.edu/~glupyan/
Lupyan, G.
(2008). The Conceptual Grouping Effect:
Categories Matter (and named categories matter more). Cognition, 108: 566-577
Abstract
Do conceptual
categories affect basic visual processing? A conceptual grouping effect for
familiar stimuli
is reported using a visual search paradigm. Search through conceptually-homogeneous
non-targets was
faster and more efficient than search through conceptually-heterogeneous
non-targets. This
effect cannot be attributed to perceptual factors and is not explained by a
long-term representational reorganization due to perceptual-learning. Rather, conceptual
categories seem to modulate visual representations dynamically, and are
sensitive to task-demands. Verbally labeling a visual target further
exaggerates the degree to which conceptual categories penetrate visual
processing.
_
Keywords: Concepts; Categories; Visual search; Labels; Top-down effects;
Visual processing; Attention
Lupyan,
G. (2008). Taking
symbols for granted? Is the discontinuity between human and non-human minds the
product of external symbol systems? Commentary on Penn, Povinelli, & Holyoak. Behavioral
and Brain Sciences, 31: 140-141. doi:10.1017/S0140525X0800366X.
Abstract:
The target article provides a convincing argument that
nonhuman animals cannot process role-governed rules, relational schemas, and so
on, in a human-like fashion. However, actual human performance is often more
similar to that of nonhuman animals than Penn et al. admit. The kind of rule-governed performance the authors take for granted
may rely to a substantial degree on language on external symbol systems such as
those provided by language and culture.
Nonhuman
and human brains are made of the same stuff. Yet, as Penn et al. point out,
there appear to be deep discontinuities between them. Owing to nonlinear
interactions between genotypes, environment, and the resulting phenotypes, functional
discontinuities are a common product of continuous evolutionary tinkering. At
issue is whether apparent discontinuities in human mental function result
directly from biological adaptations such as the “supermodule” hypothesized by
the relational reinterpretation (RR) hypothesis or whether human mental
abilities – differing quantitatively from those of nonhuman animals – are made qualitatively different by external symbol systems made
possible by language, culture, and education.
At
the same time as Penn et al. present the evidence against symbolic thinking in
nonhuman animals, they tacitly
assume
that human cognition is innately symbolic and propositional. For instance, they
claim that the “propensity to evaluate [similarity] based on causal-logical and
structural characteristics rather
than on shared perceptual features appears quite early and spontaneously in all
normal humans” (sect. 2.1, para. 1). Yet, one of the authors has himself argued
that generating spontaneous analogies poses substantial challenges even for
adults who can be easily misled by perceptual similarities (Gick & Holyoak
1980).
Although
subsequent work went on to provide numerous demonstrations of children’s and
adults’ sensitivity to structural relations (e.g., Holyoak et al. 1984), it is
not obvious that this type of reasoning arises spontaneously. For instance, Gentner
and colleagues (Kotovsky & Gentner 1996; Rattermann & Gentner 1998b)
have argued for the role of relational labels aligning object representations:
Hearing three differently sized objects referred to as “daddy, mommy, and baby”
seemed to highlight the size relationship among the objects, enabling the 4- to
5-year-old children to transfer the relation to new objects. Without the
relational labels, the relationship among the objects remained opaque. Namy and
Gentner (2002) further argued that hearing common labels for objects
facilitates taxonomic choices, leading children to group objects in more
abstract ways (although Penn et al. mention some of this evidence, their
dismissal of it is perhaps premature). Importantly, there is evidence that
language
is not only used as a “training tool,” but may continue to play an online role
in relational thinking, as
suggested
by studies using patients with linguistic impairments.
For
instance, the patient LEW (Druks & Shallice1996), whose primary impairment
is severe anomia showed a similar pattern of performance to that of 4- and
5-yearold children on tasks requiring relational reasoning. The
addition
of meaningful labels for stimuli induced a similar increment in performance to
that found in children
(Davidoff
& Roberson 2004). It seems that when external aids (here, words) are
unavailable, performance becomes more concrete and, to a greater degree, driven
by perceptual similarities.
Humans
can certainly reason analogically and perform relational judgments. The critical
question is where these
abilities
come from. Are they the natural outcomes of the human genome? Or are they made
possible by external
aids such
as the use of relational language? Penn et
al. Correctly point out that “normal human cognition clearly
depends
on normal linguistic capabilities” (sect. 9.3.1, para.1). It remains possible that human performance that is
qualitatively
different from nonhuman performance may depend on an
immersion in human culture and language.
The
evidence discussed in the target article fails to rule out this possibility.
The
authors’ assumption of innate symbolic reasoning by humans is also apparent in
the section on language in
which
Penn et al. claim that it is “widely recognized that the ability to freely
generalize relational operations
over
role-based variables is a necessary condition for using human languages” (sect.
3, para. 1). Although many researchers do hold this view, there is substantial
evidence to the contrary. Some of this evidence is reviewed in the very article
used by the authors to support their contention: Gomez and Gerken (2000). For
instance, both infant and adult learners become more sensitive to the invariant
structure (longdistance dependencies) in an artificial-grammar learning task when
the variability of the intervening elements is increased (Gomez 2002) – the
kind of token-based performance Penn et al. argue is characteristic of the
performance of nonhuman
animals
(e.g., sect. 2.2., para. 2). Penn et al.’s discussion of language acquisition
also omits the work on construction grammars (Goldberg 2006) and item-based
learning (Tomasello 2003), which have offered ample demonstrations that
children’s language learning is intensely shaped by specific examples both at
the lexical and syntactic levels.
Computational
modeling provides sufficiency proofs that item-based learning can produce the
appearance of abstract role-based categories (Elman 2004). Evidence also
indicates that adult language comprehension, rather than demonstrating knowledge
of abstract role fillers (e.g., noun and verb phrases) instead demonstrates
fluid interactions between word-specific knowledge and syntactic frames (Hare
et al. 2003; 2004). Thus, although it remains to be explained how humans
formulate explicit theories about language, actual human language use may rely
less on abstract rules than the authors admit.
The
human ability to reason about unobservable causes, to draw inferences based on
hierarchical and logical relations, and to formulate highly abstract rules is not
in dispute. Much of this thinking is compatible on an intuitive level with Penn
et al.’s RR hypothesis. But although it is indeed “highly unlikely that the
human ability to reason about higher-order relations evolved de novo and
independently with each distinctively human cognitive capability” (sect. 11,
para. 7), it is not unlikely that such uniquely human abilities depend on the
use of external symbol systems. The ability to invent such systems and benefit
from them in turn may depend on quantitative improvements in a range of
domains: memory, imitation, shared attention, sequence learning, and so on
(Elman 2005). The hypothetical child magically kept alive by itself on a desert
island will inherit these quantitatively superior abilities in a range of cognitive
domains. But would this child have all the abilities Penn et al. list as being
uniquely human in the absence of the scaffolding afforded by external symbol systems
offered by language and culture more broadly? The evidence that Penn et al.
offer is insufficient to dismiss the conclusion that such a child would “not
differ very much” from other great apes (Tomasello & Rakoczy 2003).
Although the authors provide a compelling demonstration for an insensitivity to
structural relations and the use of symbols by nonhuman animals, in taking for
granted the biological basis for these abilities in human animals, the very
premise of a biologically based fundamental discontinuity between human and
nonhuman minds remains unfulfilled.
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