Research Article
Research Article
When Development and Learning Decrease Memory Evidence Against Category-Based Induction in Children Vladimir M. Sloutsky and Anna V. Fisher
The Ohio State University
ABSTRACT—Inductive inference is crucial for learning: If one
learns that a cat has a particular biological property, one could
expand this knowledge to other cats. We argue that young
children perform induction on the basis of similarity of com-
pared entities, whereas adults may induce on the basis of cat-
egory information. If different processes underlie induction at
different points in development, young children and adults
would form different memory traces during induction, and
would subsequently have different memory accuracy. Experi-
ment 1 demonstrates that after performing an induction task,
5-year-olds exhibit more accurate memory than adults. Experi-
ment 2 indicates that after 5-year-olds are trained to perform
induction in an adultlike manner, their memory accuracy drops
to the level of adults. These results, indicating that sometimes 5-
year-olds exhibit better memory than adults, support the claim
that, unlike adults, young children perform similarity-based
rather than category-based induction.
The ability to make inductive generalizations is crucial for learning: If
one learns that a cat has a particular unobserved biological property,
one could extend this knowledge to other cats, and possibly to other
mammals. Furthermore, by some accounts, ‘‘inductive inference is the
only process . . . by which new knowledge comes into the world’’
(Fisher, 1935/1951, p. 7).
There is much evidence that even infants and young children can
perform simple inductions (Baldwin, Markman, & Melartin, 1993;
Gelman & Markman, 1986; Sloutsky, Lo, & Fisher, 2001; Welder &
Graham, 2001). However, the representations and processes under-
lying this ability remain unclear.
According to one view, people, including young children, hold
several conceptual assumptions that drive their induction (see Keil,
Smith, Simons, & Levin, 1998, and Murphy, 2002, for reviews of these
assumptions). In particular, people hold a category assumption—they
assume that each individual entity is a member of a class or category,
that count nouns refer to categories, and that members of the same
category share many unobserved properties. Conceptual assumptions
are a priori—they are not learned, but are rather a precondition of
learning, and are present early in development (Gelman & Hirschfeld,
1999; Keil et al., 1998). In the course of induction, people first
identify presented entities as members of categories and then perform
inductive inferences on the basis of categorization (Gelman, 1988;
Gelman & Markman, 1986). Therefore, when presented with a rabbit
and told that it has hollow bones inside its body, a child is more likely
to generalize this property to another rabbit than to a dog because the
child (presumably) understands that both rabbits belong to the same
category, and members of the same category share many properties. It
has been argued that this tendency to perform induction on the basis
of categorization, or category-based induction, is especially pro-
nounced when entities are members of familiar categories (Davidson
& Gelman, 1990). In short, according to this view, induction is a
function of categorization, whereas categorization is a function of a
priori conceptual assumptions.
According to another view, young children perform induction (as
well as categorization) by detecting multiple correspondences, or
similarities, among presented entities (e.g., see Jones & Smith, 2002;
McClelland & Rogers, 2003; Sloutsky, 2003; Sloutsky et al., 2001).
Because members of a category often happen to be more similar to
each other than they are to nonmembers, young children are more
likely to induce unobserved properties to members of the category than
to nonmembers. According to this view, induction and categorization in
young children are variants of the same process, which is driven by the
detection of multiple correspondences rather than by a priori con-
ceptual assumptions. Furthermore, conceptual knowledge often found
in adults (e.g., knowledge that entities are members of categories) is
not a priori, but is a product of learning and cognitive development.
Learning accounts of conceptual knowledge support this position,
while weakening the claims that conceptual knowledge is a priori. For
example, it has been claimed that young children’s tendency to use
similar shape as a reliable categorization cue is a product of a priori
conceptual knowledge (Diesendruck & Bloom, 2003; Soja, Carey, &
Spelke, 1991), whereas a convincing learning account of this shape
bias (Smith, Jones, Landau, Gershkoff-Stowe, & Samuelson, 2002) has
weakened the a priori claims by rendering them unnecessary.
Address correspondence to Vladimir M. Sloutsky, Center for Cogni- tive Science, 208C Ohio Stadium East, 1961 Tuttle Park Place, The Ohio State University, Columbus, OH 43210; e-mail: sloutsky.1@ osu.edu.
PSYCHOLOGICAL SCIENCE
Volume 15—Number 8 553Copyright r 2004 American Psychological Society
Overall, the two positions have several fundamental differences.
According to the former position, when entities are members of fa-
miliar categories, induction is a function of categorization, and cate-
gorization is a function of conceptual knowledge. Therefore, induction
is a function of conceptual knowledge. In addition, conceptual
knowledge is a priori rather than learned. According to the latter
position, early in development induction and categorization are a
function of perceptual similarity among entities, whereas conceptual
knowledge is a product of learning and development. Thus, the two
positions assume different kinds of processing underlying induction
and different developmental courses of induction and categorization.
One way of contrasting these theoretical positions is to compare pre-
dictions derived from them. For example, there is evidence in memory
research that spontaneous categorization of items may lead to memory
distortions, such as false recognition of critical lures, or nonpresented
items that belong to the same category as previously presented items
(Koutstaal & Schacter, 1997). These distortions may occur because
participants form category-level or gist representations, whereas de-
tails of each individual item are not encoded or are encoded poorly
(Brainerd, Reyna, & Forrest, 2002; Koutstaal & Schacter, 1997). When
participants are required to focus on perceptual properties of items,
they amply encode individual items, thus exhibiting accurate memory
(Marks, 1991; McDaniel, Friedman, & Bourne, 1978).
Thus, similarity-based induction and category-based induction may
result in differential remembering of information presented during an
induction task: Whereas similarity-based induction may lead to accu-
rate memories for perceptually distinct individual items, category-based
induction may result in memory distortions, such as poor discrimination
of presented items and critical lures. Therefore, if an induction task
precedes a memory test, the memory test would reveal processing un-
derlying induction. If people perform category-based induction and
form category-level memory traces, their ability to discriminate items
seen during the induction task from critical lures should be poor
(compared with their performance on a baseline no-induction task).
However, if they perform similarity-based induction, they should amply
encode perceptual information, forming item-specific memory traces,
and their discrimination should be as high as the baseline level.
It has been argued that when entities are members of familiar
categories, adults may perform induction in a category-based manner
(Osherson, Smith, Wilkie, Lopez, & Shafir, 1990), in which case an
induction task should attenuate their recognition memory compared
with the baseline. In contrast, if young children perform induction in a
similarity-based manner, they should exhibit high accuracy in both
baseline and induction conditions. Thus, following an induction task,
young children may exhibit greater memory accuracy than adults. The
prediction is nontrivial because typically adults’ memory is markedly
more accurate than that of young children (see Schneider & Bjork-
lund, 1998, for a review).
If adults’ induction with familiar categories is indeed category
based, whereas young children’s induction is similarity based, how
does this category-based induction develop? The category-based po-
sition argues that conceptual knowledge (e.g., the category assump-
tion) is a priori rather than learned (Gelman & Hirschfeld, 1999; Keil
et al., 1998). However, providing a learning account of category-based
induction weakens this position by rendering the a priori nature of
conceptual knowledge unnecessary.
To test the target prediction, we conducted Experiment 1, in which
we compared the effects of an induction task on recognition memory of
5-year-olds and adults. In Experiment 2, we trained 5-year-olds to
perform category-based induction and examined the effects of training
on their recognition memory.
EXPERIMENT 1
Method
Participants
Participants were 77 young children (M age5 5.43 years, SD5 0.28
years) and 71 introductory psychology students (M age5 19.3 years,
SD5 1.33).
Materials, Design, and Procedure
Materials were 44 color photographs of animals presented against a
white background (see Fig. 1 for examples of the stimuli). During the
study phase, participants were presented with 30 pictures, 1 picture at
a time, from three categories (10 cats, 10 bears, and 10 birds). During
the recognition phase, they were presented with 28 pictures, 1 picture
at a time, and were asked whether they had seen each exact picture
during the study phase. Half of the recognition pictures had been
presented during the study phase, and the other half were new pic-
tures. These recognition pictures also represented three categories:
cats (7 old and 7 new), bears (all 7…
