Cushman Oxymoron
Cushman Oxymoron
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Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
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Is cognitive neuroscience an oxymoron? 2
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
between input and output of a human chooser of theory they seek to advance, this would beg
over time. Such theories achieve descriptive the question of whether neuroscience methods
adequacy, in the sense that they accurately (e.g., cognitive neuroscience) can inform
describe and predict human behavior (Chomsky, cognitive theory. The answer would be
1965). Cognitive theories, in contrast, guaranteed to be “no” for a trivial reason: Any
additionally achieve explanatory adequacy. That study using apparent “neuroscience” methods to
is, they aim to characterize the set of internal answer cognitive questions would simply have
representations and computations that provide been “cognitive” research all along, by definition.
an explanation for the reliability of descriptive
relations between input and output. Thus, if 1.3 What is “important”?
neuroscience plays an important role in cognitive
research, it must do so by constraining theories What does it mean to say that neuroscience
of representation and computation. has played, or could play, an “important” role in
the development of cognitive theories? This
1.2 What is neuroscience? question is most interesting if it is reframed
pragmatically: If we are interested in developing
Neuroscience is the study of the nervous an accurate model of cognition, is it a useful
system, including its physical and biological strategy to seek evidence from neuroscience
properties. Like all cognitive theories, many methods?
neuroscience theories are motivated by the Thus, neuroscience could be a useful source
ultimate desire to explain the functional of evidence without being sufficient for the
organization of the mind. Yet theories of development of cognitive theories. In other
neuroscience can be distinguished from words, having a complete theory of cognition
cognitive theories in part because they are stated may require us to know about more than just the
over physical and biological terms (or explicit brain. A complete cognitive theory of visual
abstractions from them) rather than over processing, for instance, might depend upon
exclusively representational and computational information about typical scenes in natural
terms. contexts (i.e., the things we see), as well as the
Neuroscience comprises not only a set of functional role of vision in guiding human
theories, but also a set of methods. A neurosci- interactions in the world. Whether cognitive
ence method involves either manipulating or theories must be stated over terms external to
measuring neural processes directly. In other the nervous system is a matter of significant
words, it either involves an intervention upon philosophical controversy. But, even if we adopt
neural processes in a manner that is not the position that a theory of mental representa-
mediated by ordinary perception (e.g., neural tion and computation must be stated partially
stimulation by electrical or magnetic forces, over terms external to the nervous system, the
lesion by natural or artificial means, experi- neurosciences could still play a useful role in
mental control of gene expression, etc.), or else it developing those theories.
involves measuring neural processes in a manner Similarly, neuroscience could be a useful
that is not mediated by ordinary behavior (e.g., source of evidence in developing cognitive
EEG, MRI, single unit recording, etc.). In theories without being a definitive source of
contrast, in “behavioral” methods, the evidence. (Indeed, it’s hard to say whether any
experimenter’s access to mental processes is form of scientific evidence is ever definitive).
mediated by ordinary perceptual and behavioral Presumably neuroscience will constrain
processes. cognitive theories via inference to the best
It is not necessary that neuroscience meth- explanation. That is, certain cognitive theories
ods are used exclusively to inform neuroscience will provide a better explanation for the
theories, or that behavioral methods are used neuroscience evidence, others will provide a
exclusively to inform cognitive theories. This worse explanation, and we can use this to inform
point is crucial: If we defined methods in terms our assessment of the quality of the cognitive
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Is cognitive neuroscience an oxymoron? 3
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
theories. In this method of reasoning the For instance, there are detailed theories of the
neuroscience evidence can play an important cellular mechanisms that enable neuronal firing;
role in adjusting our assessment of the however, these are unlikely to be sufficiently
probability of cognitive theories being correct, related to mental representation and computa-
even without definitively endorsing or defeating tion to play an important role in cognitive
any particular theory. research. Even if every cognitive representation
Neuroscience could also be a useful source of is encoded by the firing of neurons, this does not
evidence without being necessary for the mean that a theory of the mechanics of neural
development of cognitive theories. This point is firing at the cellular level informs a theory of
obvious enough. If I want to know what color cognitive representation.
my socks are, looking at them would be a useful Consider a slightly different question,
source of evidence, but it is certainly not a however: If a scholar wishes to understand the
necessary source of evidence. I could buy a influence of Uncle Tom’s Cabin on American
camera, hire a film crew to shoot a movie of my attitudes towards slavery, would it be useful for
socks, show it to my wife and ask her what color her to read the book—i.e., to interact directly
she sees. But even if it isn’t necessary for me to with it as a physical object? Presumably it
look at my own socks to determine their color, it would, simply because this would provide
could certainly be useful. relevant information about its contents, which
Finally, it might be the case that neurosci- would in turn inform a theory of its influence.
ence is a possible source of evidence without Reading the book might not be necessary. The
being a practical one. For instance, the film- scholar could rely on indirect sources of
crew approach is a possible method of attaining evidence about its content, and many of the
evidence about the color of my socks, but it isn’t inferences she would wish to draw about its
a very practical one. Although practicality is influence wouldn’t depend on knowing its
important, I won’t address it much further. precise contents anyway. Nor, of course, would
reading the book be sufficient to answer all the
2. A priori analysis scholar’s questions. But if the scholar had never
read the book before, and if it sat on her shelf,
The brain is the principal physical substrate surely she would be crazy not to pick it up.
of human cognition. Doesn’t this guarantee that This analogy highlights the utility of distin-
theories of brain function will be relevant to guishing between neuroscience theory and
theories of cognition? In fact it does not, as a neuroscience methods. A general theory of
simple analogy illustrates. Consider a scholar “books” as a physical object might be stated over
who wishes to develop a theory of the influence terms irrelevant to the informational content of
of Uncle Tom’s Cabin on American attitudes any given book—e.g., principles of chemical
towards slavery. This novel was distributed in bonding, methods of manufacture, etc. Such
printed books, and so the influence of its content theories would typically be useless to a scholar
upon readers was fully mediated by physical interested in their informational content. Yet,
objects. Would it be useful, then, for the scholar the “method” of interacting physically with
to investigate properties of those objects, such as particular books (i.e., reading them) is obviously
their material composition (paper and ink) or a very useful method of understanding their
method of manufacture? Probably not: This informational content. Similarly, it might be the
approach would fail because general information case that theories of neuroscience typically
about the material composition of the book or its generalize over properties of neural systems that
method of manufacture are not sufficiently are not particularly informative about mental
related to the information contained in the book, organization at the level of representation and
which is what shaped American attitudes computation. Yet, interacting directly with the
towards slavery. physical substrate of a neural system might be a
The same is true for many properties of very useful method of learning about the
neural systems when applied to cognitive theory.
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Is cognitive neuroscience an oxymoron? 4
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
representations and computations instantiated in work, which is an ideal case study of the
one. potential for neuroscience to advance cognitive
Of course, reading the brain is not as easy as research.
reading a book. If your uncle Tim is acting oddly Feed-forward visual processing begins when
and you want to understand why, it probably light hits a photoreceptor in the retina. These
makes more sense to use behavioral methods photoreceptors relay through another layer of
(i.e., observing the relationship between cells to eventually activate retinal ganglion cells,
perceptual inputs and behavioral outputs) than which transmit information from the eye to the
to crack open his head and take a close look at brain. In the years surrounding World War II, a
his brain. In order for the “direct” investigation number of researchers performed single-unit
of the neural system to usefully inform recordings of the evoked response of retinal
psychology, we must have theories capable of ganglion cells during the presentation of brief
relating physical data to cognitive theories, and visual stimuli to the eye (Barlow, 1953; H.
instruments capable of collecting that data. Hartline, 1940; H. K. Hartline, 1938; Kuffler,
Given such theories and instruments, however, it 1953). This line of investigation lead to a pivotal
is hard to see how neuroscience methods could characterization of a type of receptive field
fail to be informative for cognitive research. common to many retinal ganglion cells: “center
surround” (Figure 1).
3. A case study
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Is cognitive neuroscience an oxymoron? 5
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
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Is cognitive neuroscience an oxymoron? 6
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
neuroscience, however, it is easy to grasp how neuroscience will, of course, tend to cite that
pivotal the role of neuroscience evidence was in very neuroscience. Thus, we might ask whether
this case. A characterization of the receptive cognitive research that cites neuroscience is
fields of individual neurons across multiples subsequently more cited. This evidence would
stages of representation enabled Hubel and be consistent with the hypothesis that cognitive
Weisel to posit an account of the representations research that is influenced by neuroscience is of
and computations contained in early visual a higher quality (or at any rate more influential),
processing that had not really been entertained although it is also consistent with some
in any serious way by prior theorists. In other alternatives.
words, they made a big step, relatively fast, and Of course, it is crucial that this hypothesis is
there is little indication that the step would soon tested on papers that are unambiguously devoted
have occurred without reliance on neuroscience. to the development of cognitive theory. It is
Above, I introduced the conceptual distinc- possible, for instance, that neuroscience research
tion between neuroscience theory and is more cited that cognitive research, but this is
neuroscience methods. The key contribution of not the question. Our goal is not to establish
Hubel and Weisel’s research to a cognitive whether neuroscience is influential in general.
theory of visual processing appears to have been Rather, the goal is to assess whether neurosci-
their use of neuroscience methods, not their ence improves cognitive research. Thus, we
development of a general theory of neuroscience. want to consider only articles that are cognitive
In other words, the information they obtained research, asking whether those that cite
about neural responses did not influence neuroscience (i.e., are influenced by it) are
cognitive theory by way of some general theory subsequently more cited (i.e., are of a higher
of the nervous system—i.e., a theory that quality, or more influential).
generalized over physical rather than We assessed this question in a sample of
informational properties of the brain. Hubel and articles drawn from the journal Cognition. This
Weisel instead moved directly from data about journal publishes articles almost exclusively on
the neural system, collected by neuroscience cognition. It publishes almost no research
methods, to theory of information processing. employing neuroscience methods (e.g. fMRI),
Although their theory of information processing and the few articles that do employ neuroscience
could also be construed as a “neuroscience methods are designed to address theories of
theory”—after all, it described the implementa- cognition. Indeed, among the sample of articles
tion of a algorithm in terms of the firing of and that we targeted, a search on the Thomson
connections between neurons—it was no less a Reuters Web of Science did not reveal any that
theory of cognition. By marrying an algorithmic included “fMRI” in its title or abstract. The
specification of cognitive processing to a audience of Cognition is primarily psychologists,
biological plausible neural implementation and it is among the more influential and widely
(Marr, 1982) it was, without irony or contradic- read journals specific to the field of cognitive
tion, an instance of true “cognitive neurosci- psychology.
ence”. This analysis focuses on articles published
during the calendar years 2008, 2009 and 2010.
4. Quantitative analysis This affords a large sample of published articles
(N = 540) for which we could obtain adequate
If neuroscience is important to the develop- citation information from the Web of Science.
ment of cognitive theories, then cognitive We chose this range of dates because it seemed
research that is directly informed by neurosci- late enough for the published articles to have
ence will tend to be of a superior quality. How potentially benefitted from the explosive growth
can we test this hypothesis by quantitative of cognitive neuroscience in the preceding
analysis? A common proxy for the quality of decade, but early enough to have amassed a
scientific research is its citation index. And, meaningful number of citations representative of
cognitive research that is “influenced” by their quality.
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Is cognitive neuroscience an oxymoron? 7
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
For each article we recorded the number of sample. This pattern of correlations may
Web of Science indexed citations (hereafter obscure the predicted effect of neuroscience
“citations”) through August 2015 (the date at references on subsequent citations, and so it is
which this manuscript was initially prepared); important to statistically control for the effect of
this is our measure of the article’s quality and time. Third, articles that contained more
influence. We used an automated text extraction references overall were more likely to contain at
algorithm to identify the references cited in each least one reference to neuroscience, and also to
article PDF (hereafter, “references”). This receive more citations (e.g., perhaps because of
algorithm identified 21,159 references, including variable rates of citation across subdisciplines,
many to the same sources. We then categorized reciprocity among authors, a correlation
references targeting “neuroscience” (versus not) between an exhaustive literature review and
by assessing whether each referenced article was article quality, etc.). This pattern of correlations
published in any of 62 neuroscience journals, or may artificially inflate the predicted effect; again,
whether its title contained word stems it is important to statistically control for it.
associated with neuroscience (e.g. “Neur”, Thus, we performed a regression that
“Brain”, etc.). predicted the natural logarithm of the number of
The sample of articles we analyzed were citations received by each article in our sample.
cited an average of 31 times each. Out of 540 We included three predictors: a dichotomous
total articles, 311 (58%) referenced at least one variable that coded whether each article
neuroscience article, while 229 (42%) referenced contained any references to neuroscience, a
none. Articles that contained at least one variable coding the year of publication, and the
neuroscience reference received an average of 34 total number of references contained in each
citations, while those that contained no article. Again, we found a statistically significant
neuroscience references received an average of effect indicating that articles that referenced
26 citations, which is a statistically significant neuroscience were more likely to receive
difference t(538) = -2.88, p < .005. In other subsequent citations, p < .005, after controlling
words, articles that referenced neuroscience for the other two predictors.
tended to receive about eight more citations on Although we find clear evidence in this
average than articles that did not, an increase of model that referencing any neuroscience is
31% in the frequency of citation. A comparison correlated with a higher citation index, we do
of the most cited to least cited articles helps to not find evidence that referencing more
illustrate this trend. Among the 20 most cited neuroscience helps. Specifically, after
articles (mean = 148 citations), 17 contained at controlling for the presence versus absence of
least one neuroscience reference. In contrast, any neuroscience reference, there is no further
among the least cited articles (mean = 3 statistical relationship with the specific number
citations), only 9 contained at least one of neuroscience references (p > .50) or the
neuroscience reference. proportion of neuroscience references out of all
This analysis can be improved in a few references (p > .50). On the one hand, this
simple ways. First, citations are not distributed provides some evidence against the hypothesis
normally across this sample of articles; rather, that articles referencing neuroscience are cited
the distribution is highly right skewed, violating more only when they actually contribute to the
an assumption of the parametric statistical tests neuroscience literature (i.e., report neuroscien-
we employed to analyze our data. A log tific results, address neuroscientific theories,
transformation of citation counts produces an etc.) Were this the case, presumably an article
adequately normally distributed dependent that cites many neuroscience findings (and thus
variable. Second, as might be expected, articles more likely contributes to the neuroscience
published earlier (e.g. 2008) tended to receive literature) would receive more citations than an
more citations than articles published later (e.g. article that cites only one or two neuroscience
2010), while the likelihood of neuroscience findings (and thus likely does not contribute to
references also increased over this range in our the neuroscience literature). On the other hand,
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Is cognitive neuroscience an oxymoron? 8
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
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Is cognitive neuroscience an oxymoron? 9
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
This hypothesis is more likely, and also harder to articles that did not refer to neuroscience). This
rule out based on our data. Because the citation analysis, however, is compromised by a marked
advantage that we observe is not eliminated reduction in statistical power.
when controlling for the total number of In summary, our analysis provides strong
citations, we can at least provide some evidence evidence that references to neuroscience articles
against a pure effect of peer-to-peer reciprocity are associated with higher citation rates for
in citation (assuming that neuroscientists are no cognitive research in Cognition. Yet, this data is
more prone to such reciprocity than non- compatible with a number of rival hypotheses
neuroscientists), but other versions of the and does not provide exclusive support the
hypothesis are not addressed by this analysis. conclusion that neuroscience has an important
There is a third version of this alternative influence on cognitive research.
that is perhaps the most likely, but is friendly to
the overall claim that cognitive research is 5. Conclusion
improved by engagement with the neuroscienc-
es. Possibly, cognitive research that engages Cognitive neuroscience aims to characterize
seriously and directly with neuroscience is also the interface between computation and biology,
more useful to neuroscientists who are working and it is not an oxymoron. A priori, there is good
on cognitive questions—i.e., cognitive reason to believe that cognitive neuroscience
neuroscientists. For instance, research that uses will advance cognitive theory. Although it is not
behavioral methods to investigate early visual clear whether “theories” of neuroscience will
representations would likely benefit from often play this role, there is every reason to
research on this topic using neuroscience believe that neuroscience methods will be
methods; in turn, it is especially likely to inform pivotal. This depends, of course, on the
future research using neuroscience methods. In existence of theories that map between physical
this case, our effect might be driven by citations properties of the brain and computational
from neuroscientists, and yet it would still be properties of the mind. A case study of an early
diagnostic of the underlying quality and broad advance in cognitive neuroscience, the mapping
applicability of the research for the development of receptive fields in the retinal ganglion and
of cognitive theories. early visual cortex, shows that this approach can
Based on the set of citation records available succeed in practice. This case study underscores
to us we could not develop a reliable method to the utility of neuroscience methods for
directly assess whether our effect was due describing representations and computations
entirely to enhanced rates of citation by that are many stages of processing removed from
neuroscience for those articles in our sample that behavior and, thus, difficult to characterize by
referenced neuroscience. The most relevant behavioral methods alone. Of course, this case
evidence we found targets a different, but related study may be anomalous. Yet, in an analysis of a
question: Are references to neuroscience related sample of articles developing cognitive theories,
to increased citation from articles that are not we find that references to past neuroscience
neuroscience? In order to assess this, we research are associated with a greater impact as
analyzed the number of citations for each article measured by citation index. This is at best an
in our sample, focusing exclusively on indirect proxy for the underlying “quality” of
subsequent articles also published in Cognition. cognitive research, however, and the evidence
In other words, we asked, “For three years’ presented here is consistent with several
worth of articles published in Cognition, if they alternative hypotheses.
referenced neuroscience, were they then more Each of the methods used above—a priori
likely to be cited by subsequent articles also analysis, case study and quantitative analysis—
published in Cognition?” In this case we found has its own drawbacks. Together, however, their
no significant difference in citation rates; indeed, complementary strengths provide a unified
if anything the citation rates trended in the account of the important role that evidence from
opposite direction (i.e., more citations for
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Is cognitive neuroscience an oxymoron? 10
Forthcoming: Current Controversies in Philosophy of Cognitive Science, Eds. S. Cullen, S.J. Leslie & A. Lerner
Acknowledgements
References
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