LINGUIST List 14.986

Thu Apr 3 2003

Review: Cognitive Science/Semantics: Murphy (2002)

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  1. C A Ankerstein, The Big Book of Concepts

Message 1: The Big Book of Concepts

Date: Wed, 02 Apr 2003 22:38:25 +0000
From: C A Ankerstein <hcp02caasheffield.ac.uk>
Subject: The Big Book of Concepts

Murphy, Gregory L. (2002) The Big Book of Concepts, MIT Press, A
Bradford book.

Announced at http://linguistlist.org/issues/13/13-2894.html

Carrie Ankerstein, Department of Human Communication Sciences,
University of Sheffield, England.

OVERVIEW

Gregory Murphy's ''Big Book of Concepts'' is organized around the
issues that surround the study of concepts, i.e. it is not organized
around the various theories of concepts. After the introductory first
chapter, the theories of concepts are discussed in chapters 2 and 3
and the following chapters describes an issue or set of phenomena
within concepts, these chapters end with a discussion of how each
theory of concepts would handle the issue.

The book is aimed towards an advanced undergraduate or beginning
graduate student audience. Murphy assumes that the reader has a
general knowledge of experimental psychology and some experience with
cognitive psychology, though knowledge about concepts is not assumed.

The chapters are self-contained and may therefore be read out of
sequence. Though this is the case, I think it may be useful to read
some chapters before others. For example, Murphy discusses ''Knowledge
Effects'' and ''Induction'' in separate chapters, though these issues
come up again in later chapters. In those later chapters, Murphy is
careful to give adequate background in these issues, however the
reader may find it more fulfilling to have read these chapters
beforehand. Also, since many of the issues discussed in the book are
discussed with reference to the theories of concepts, it is advisable
to at least glance at the theories that Murphy discusses (see Chapters
2-4).

SYNOPSIS

In the first chapter the ''Introduction'', Murphy outlines some
fundamental terminology: a ''concept'' is a mental representation of
classes of things and a ''category'' refers to the classes
themselves. He also states the purpose of his book: ''[it] is not so
much to tell you all about concepts as to provide some kind of basis
to your continuing acquisition of knowledge'' (p. 8).

Chapter 2: Typicality and the Classical View of Categories 
In this chapter, Murphy discusses the Classical or Definitional View
of concepts, which states: concepts are composed of necessary and
sufficient features. On this view, a concept is either an X or it
isn't and all concepts that are X are all on par with each other -- no
member is better than the other. It is these predictions, however
that proved disastrous for the Classical View as typicality effects
were found and the mythical ''necessary and sufficient'' features
weren't.

Chapter 3: Theories After the fall of the Classical View arose the
Prototype View which states that each category is represented by a
single prototype or best example. Very typical members of the category
will share the most overlap of features with the prototype and
atypical members will share only a few features and may share other
features with another prototype of another category (e.g. tomato as a
fruit and/or vegetable). Thus the Prototype View solves many of the
problems of the Classical View: there are no defining features and
typicality effects are predicted. However, this view is not without
problems either.

Another possibility is the Exemplar View: concepts are defined by
personal experience with that concept. For example, ''dog'' is the set
of all dogs that the reader of the word ''dog'' has encountered. The
obvious argument against this is that one does not run through all
dogs one has seen, instead there is a ''general'' idea of dogs.

The last view discussed is the Knowledge Approach which argues that
concepts are part of our general understanding of the world or our
mental theories about the world. This view is often called the
Theory-Theory View.

Chapter 4: Exemplar Effects and Theories The issue discussed in this
chapter is that of generalization or knowing things in general without
thinking about a specific example. Murphy discusses two different
approaches to this view:

1. Exemplar Effects: when people encounter a new item, they use a
 particular remembered exemplar to categorize the new item.
2. Exemplar Models: a formal (usually mathematical) approach to
 similarity quantification.

In this chapter, Murphy also returns to the ''prototype or exemplar''
question that arose in the preceding chapter: are representations best
examples or generalized feature summaries. The question is not
answered, but the discussion is though provoking.

Chapter 5: Miscellaneous Learning Topics 
The chapter is purposely named. In this chapter very specific issues
are discussed as well as broader issues that affect other phenomena
discussed in later chapters. These include: base-rate neglect in
category learning, feature correlations in concepts, category
construction and category use and the implications that follow.

By ''base-rate'' Murphy is referring to what may be considered a
feature that occurs most frequently in a given category, e.g. bird
often fly but mammals don't. In category learning, people will
generally ignore the base-rate or standard set of features and focus
on more defining features, e.g. they won't focus on the fact that
birds often fly, but look for something more distinctive.

Feature correlation refers to the fact that an item is not a
collection of unrelated features, instead these often go together,
e.g. birds have wings and can fly, a knife has an edge and can
cut. Categories are composed of clusters of correlated features that
differ from other categories that have different clusters.

Category construction refers to a commonly used methodology in which
subjects form new categories on their own without being told by the
experimenter what forms a category. By category use, Murphy is
referring to the use of specific exemplars or use of the category as a
whole and how this use can alter the categorization of concepts.

Chapter 6: Knowledge Effects
Many studies of concept learning use novel stimuli, e.g. things people
have never seen before like dot patterns or chimera, to explore the
principles that may be applied to other categories or domains. Though
Murphy questions the relevance of such findings -- they may not be
applicable to real-life concept acquisition.

In this chapter, Murphy discusses the type of effects found in more
realistic stimuli, more specifically, background knowledge and the use
of this knowledge in concept learning. By knowledge, Murphy means the
post-hoc use of the general world knowledge people have (right or
wrong) and use to explain a category when it is being learned. For
example, upon learning that an ostrich is a bird, but it doesn't fly,
people may use their knowledge about birds, wings and flight to
rationalize a reason why ostriches don't fly: their wings are not
strong/big enough to lift the massive body. In the case of novel
stimuli, people are unable to use their knowledge about that category,
because they have never encountered it before.

Chapter 7: Taxonomic Organization and the Basic Level of Concepts
This chapter focuses on the hierarchical structure of concepts. A
taxonomy is ''a sequence of progressively larger categories in which
each category includes all previous ones'' (p. 199),
e.g. animal-mammal-dog-bulldog. Murphy discusses the phenomenon of the
basic level or preferred level of categorization, e.g. cat, dog, tool
as opposed to Siamese cat, Labrador retriever, and wrench. He
addresses the following questions: Is there evidence that people have
basic levels? Do people use such hierarchies?

As Murphy acknowledges, this is rather murky water, but claims that
there are at least two generalizations that can be made about
hierarchies:
1. People are able to learn and use taxonomic relations in order to
 draw inferences.
2. People are able to reason taxonomically about novel categories.

Chapter 8: Induction
If people were unable to make sensible inferences about new things,
there were be little advantage in knowing that something belongs to a
specific category. Categorization is not useful in and of itself, but
it is being able to apply category knowledge that is useful. Murphy
discusses ''induction'' as ''the kind of reasoning that one uses when
drawing conclusions about the category in general'' (p. 243). For
example if you were asked to check up on your neighbor's dog, you
would from your knowledge of dogs know what to do, e.g. feed and water
it, let it out, etc.

The chapter discusses various research tasks that have investigated
the kinds of inductions that people make, how people use multiple
categories when making inductions about things there are uncertain how
to categorize and the different types of methodologies used in these
experiments.

Chapter 9: Concepts in Infancy
Murphy argues that children's concepts are largely ignored in reviews
of the psychology of concepts and he offers two reasons why we should
pay attention to concept development:

1. Development speaks to one of the most central questions of
 cognitive science: how knowledge comes into being.
2. Developmental evidence may place constraints on theories of adult
 competence and performance.

Chapters 9 and 10 discuss these issues. Chapter 9 covers the
development of concepts from birth through the first year of life and
Chapter 10 covers the conceptual development of toddlers through the
early school years.

In Chapter 9, Murphy discusses many studies, focusing not only on
their findings, but also the methods used. Categorization and natural
and artificial concept learning are also discussed.

Chapter 10: Conceptual Development
In this chapter, the fundamental question is: Are children's concepts
radically different to adult concepts? After showing that children
perform similarly to adult on many of the tasks generally used in the
study of concepts, Murphy discusses the developmental counterparts of
the issues that surround adult concepts: typicality, taxonomic
organization and knowledge effects.

He concludes that though there are some differences in the content of
children's concepts and their performance on experimental tasks, there
is no radical difference between adult and child concepts.

Murphy also discusses other aspects of concept acquisition including
constraints on conceptual learning: syntactic constraints and fast
mapping. Syntactic constraints apply limits to the possible referents
of new words, e.g. Look at the quassle! In this case ''quassle'' can
only refer to a thing rather than an action. Fast mapping refers to
the ability of children to use a word after minimal exposure, e.g. 2
or 3 instances. Without such constraints, concept learning would be an
unbelievable achievement.

Chapter 11: Word Meaning
Murphy discusses the relationship between ''words'' and ''concepts''
though the distinction has not been made in preceding chapters. In
this chapter he discusses the distinction. A ''concept'' is ''a
nonlinguistic psychological representation of a class of entities in
the world'' and ''word meaning'' is ''the aspect of words that gives
them significance and relates them to the world'' (p. 385).

Murphy's own claim is that ''word meanings are psychologically
represented by mapping words onto conceptual structures'' (388) and
there are many possibilities to how this might work, e.g. there may be
a one-to-one mapping where each word is mapped onto one concept. This
is unlikely though, as soon as one begins to think about polysemy --
the multiple senses of a word such as theater can be used to refer to
the institution which puts on plays or the building in which plays are
performed. Murphy offers a more complicated, though satisfactory
relationship based on three principles which take into account the
problem of ambiguity that arises out of polysemy.

Chapter 12: Conceptual Combination
This chapter addresses the fact that we rarely deal with concepts in
isolation, instead they general come in linguistic chains, e.g. ''I
found a really great dog book yesterday'' where ''dog book'' refers to
a separate concept, combined by the concept of ''dog'' and
''book''. The question is: How do people construct complex concepts
out of these parts? The chapter is mostly a presentation of the
various models that try to explain concept combination. He concludes
with the importance of the role that knowledge plays in the
combination of concepts.

Chapter 13: Anti-Summary and Conclusions
Murphy concludes the book with issues that have not been discussed and
why, including: computational models of conceptual processes
(e.g. categorization, learning, induction), perception (the role of
perceptual information in categorization and judgments), similarity
and cross-cultural issues. After acknowledging these left-overs, he
quickly sums up the theories discussed, the messiness of the field and
future directions in the study of concepts and defends his
organization and approach in the writing of the book, e.g. focusing on
the issues surrounding the study of concepts rather than the theories
of concepts.

CRITIQUE

Murphy's book covers a lot of the more interesting issues surrounding
concepts. He adds some new insights into the field. The style is
generally light, witty and clear, though not always concise. His
approach of organizing the book according to issues and phenomena is
novel and refreshing as most books on concepts focus on theories
without integration of issues and things that affect them all.

There are, however a few things that have been surprisingly left
out. For instance, nowhere is there a discussion of the view that
concepts may not be featural representations, but instead atomistic
representations (the Conceptual Atomism View). All the theories and
discussions in the book approach concepts as featural representations,
though there is an opposing view to this. Murphy assumes a featural
approach without pausing to defend it.

Though Murphy covers the development of concepts, claiming its
importance to the study of adult concepts, he neglects to mention the
deterioration of concepts as seen in semantic dementia. Though the
issue of semantic breakdown is complicated, e.g. is access to concepts
or the conceptual store itself damaged, it does offer some very
interesting insight into the organization and content of conceptual
knowledge -- compatible with some views discussed in the book and
problematic for others.

ABOUT THE REVIEWER

Carrie Ankerstein is a PhD student in the department of Human
Communication Sciences at the University of Sheffield, England. She
has a Masters in Applied Linguistics from the University of Cambridge,
England and a Bachelor's degree in German Linguistics from the
University of Wisconsin-Madison, USA / University of Freiburg,
Germany. Her research interests include the organization and
representation of concepts in semantic memory.
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