Operativity and the superordinate categorization of artifacts

JOURNAL

OF tXPERlMENrA1.

Operativity

CHI1.D

54, 334-354 (t’)‘)?)

PSYCHOI.OGY

and the Superordinate

Categorization

of Artifacts

B. RKTO

ROBERT

ANI)

HARRY BEILIN

Relations are low tial/temporal

between in

urative cues to superordinate

and

of age-equivalent across ordinate cmplars exemplars

and

similarity, Operativity,

atypical i.e..

exemplars

establish nonfigurative relations, categorization. The present study preoperational

and

of superordinate

categorieb

similarity based in appearance or in as an emergent competence to overcome might be expected assessed the relative

concrete-operational

groups

spafig-

to contribute consistency of first

graders

two

categorization tasks employing color drawings of exemplars of supcrartifact categories. Concrete-operational subjects catcgorizcd two cxtogether on a Sample-Match Task if they had previously included both under

the

same

category

on a Category-Membership

Task.

In addition

to membership in the same category. preoperational exemplars bc typical before categorizing them Task. The cognitive levels did not differ m their

subjects required that hoth together on the Sample-Match category membership decisions.

Results

and

knowledge.

arc discussed in terms of both c I’*)~ Acddenllc PX\\. Ill‘

One of the quisition and between level late preschool This Institute doctoral

typical

figurative context.

utilization

acquisition

of superordinatc

more reliable effects in contemporary research on the acdevelopment of natural categories has been an interaction of abstraction and age. While age differences during the and early school years in taxonomic responding at the basic

research was supported by a National Research Service Award of the National of Child Health and Human Development (Grant 5T32 HDO71Y6) funding PostFellowships in the Developmental Psychology Program of the Graduate Center of

the

City University of New York. We acknowledge the cooperation of students and staff at Saint Bartholomew‘s School Northeast Philadelphia and the Fairmount Public School of Hackensack. New Jersey. Correspondence and reprint requests should be addressed to Robert Ricco at the partment of Psychology, California State University, San Bernardino. CA 92407.

in De-

SUPERORDINATE

CATEGORIZATION

335

level are no longer common (Gelman, 1988a, b; Gelman & Markman, 1986, 1987), such age effects persist at the superordinate level across a wide variety of tasks including sample-match procedures (Melkman, Tversky, & Baratz, 1981; Tversky, 1985), sorting tasks (Bjorklund & de Marchena, 1984; Horton & Markman, 1980), free recall (Puff, Tyrrell, Heibeck, & Van Slyke, 1984; Saxby & Anglin, 1983), cued recall (Whitney & Kunen, 1983, but see Melkman et al., 1981), as well as innovative inductive inference procedures (Gelman, 1988a; Gelman & WatsonO’Reilly, 1988) which have otherwise proven quite successful in revealing heretofore unrecognized preschool competencies. Early accounts of the difficulties incurred by young children on superordinate categorization tasks centered on the presumed logical structure of taxonomies (Inhelder & Piaget, 1964, pp. 110-118; Neimark, 1983; Olver & Hornsby, 1966; Osherson & Smith, 1981). It was alleged that both stipulative and natural taxonomies are based on relations of class inclusion and that a domain-general competence with the logic of classes is a prerequisite for an appreciation of how basic object concepts are included within superordinate categories (Inhelder & Piaget, 1964, pp. l-11). However, the fact that natural categories do not seem to be mentally represented as classes (Rosch & Mervis, 1975) led to a deemphasis of the role of logical abilities in the acquisition of superordinates. Any adequate account of the problematic nature of superordinate categories for preschoolers must include the diminished role of figurative similarity (Piaget, 1977) in taxonomic relations, i.e., relations among the exemplars of a category, at the superordinate level. Figurative similarity is based on configurational or static characteristics of experience and it includes perceptual similarity and cooccurrence in space or time (contextual similarity). Though supportive of taxonomic relations at the basic level (Murphy & Smith, 1982; Tversky & Hemenway, 1984), figurative similarity is often at odds with taxonomic relations at the superordinate level. Exemplars of a superordinate category can differ considerably in appearance or typical context of occurrence because category intentions include abstract functional criteria (e.g., clothing provides warmth or protection, vehicles provide transport) whose instantiation is only loosely constrained along figurative lines (Nelson, 1985, pp. 199-206; Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976; Smith, Balzano, & Walker, 1978). One index of figurative similarity is degree of typicality (Rosch et al., 1976). At all levels of abstraction, the less typical an exemplar, the less it has in common with other exemplars of a category in terms of figurative dimensions (Rips, Shoben, & Smith, 1973; Rosch et al., 1976). At the superordinate level, relations between typical and atypical category exemplars are generally low in figurative similarity (Rips et al., 1973: Rosch & Mervis, 1975). object

336

RICCO

AND

BEILIN

The singular status of the superordinate level in terms of both age effects and the independence of taxonomic relations from figurative similarity suggests that contributing to superordinate category acquisition may be a domain-general, emergent competence to suppress or overcome figurative states of affairs and establish nonfigurative similarities (Ricco, 1989). Perhaps the most widely employed measure of such a competence is Piaget’s construct of operativity (Piaget, 1977). Piaget (1977) argues that figurative knowledge cannot provide the structure or inherent organization of experience because the underlying nature of reality is not stability, but change-lawful change-which can only be accessed through cognitive transformations of figurative knowledge (Beilin, 1985; Overton, 1984). Operations, as reversible, i.e., logically coordinate, transformations, are particularly effective sources of organization (Beilin, 1983), establishing powerful forms of nonfigurative knowledge (e.g., the invariance of quantity across transformations of shape). Adult-like mental representation of superordinate categories involves nonfigurative knowledge because superordinate representation requires the construction of relations between figuratively dissimilar exemplars. Relations of similarity based on abstract properties such as commonality of function or internal composition, crucial to the acquisition and implementation of superordinate organizations (Keil, 1987). are nonfigurative similarities, the result of cognitive transformations of figurative states of affairs. Such cognitive transformations have been variously conceived as theory-driven selection or weighting of features (Keil, 1987; Keil & Batterman, 1984), the construction of causal and logical relationships to explain phenomenal clusterings or intercorrelations among features (Keil, 1987; Medin & Wattenmaker, 1987), and an imaginative application of real world knowledge in constructing plausible instantiations of functional properties (Miller, 1977). Reversibility, i.e., an operational status to cognitive transformations, has been implicated in similar cognitive transformations involved in the acquisition of physical knowledge-these include a decentering of attention from salient to less salient features and dimensions (Gold, 1987, pp. 64-70). the construction of necessary and sufficient, i.e., logical, relations among features (Inhelder & Piaget, 1964, pp. l-11), and an expansion of regularities of occurrence to cause-effect relations per se (Piaget & Garcia, 1974). Thus reversibility might be a necessary, logical attribute of cognitive transformations involved in the construction of taxonomic relations at the superordinate level. The above contention that reversibility, an emergent, logical property of thought, is implicated in superordinate category acquisition is not a claim that natural categories are mentally represented as classes, i.e., sets of exemplars meeting certain necessary and sufficient conditions, as argued by Inhelder and Piaget (1964. pp. 100-118). The proposed role for re-

SUPERORDINATE

CATEGORIZATION

337

versible transformations concerns the acquisition and not the representation of categories and is thus consistent with a nonlogical, e.g., exemplarbased, representation for natural categories. Could a competence to overcome figurative dissimilarities and establish nonfigurative similarities be primarily linguistic, rather than cognitive, in origin, as argued by language-based approaches (e.g., Markman, 1987, 1990; Nelson, 1985, pp. 177-212) to the acquisition of superordinate categories? Nelson (1985, pp. 158-159) maintains that preschoolers have difficulty with superordinate categorization because they have not yet established a semantic system of hyponymic relations (i.e., hierarchical relations within language) that is adequately differentiated from the eventbased, thematic structure of the preschool conceptual system. Once the independence of semantic representation from conceptual representation is established, the former can, in turn, facilitate development of specifically taxonomic conceptual representation. Also stressing contributions of the linguistic system to the acquisition of natural categories, Markman (1987,199O) contends that one linguistic factor facilitating the acquisition of superordinate categories is the child’s mastery of distinctions among collective, count, and mass nouns. These grammatical classes differ in whether they organize referents in terms of spatial relations, relations of similarity, or, in the case of mass nouns. a subtle mixture of both dimensions. From within the language-centered accounts of superordinate category acquisition offered by Nelson and Markman, emerging properties of the child’s language system, such as the representation of hyponymic relations and of subtle distinctions among noun classes, provide an important symbolic mode for freeing conceptual representations from spatio-temporal contexts (Nelson, 1985, pp. 163-165). The language-based account, therefore, argues that linguistic advances precede and facilitate conceptual advances, such as the emergence of a superordinate level to natural taxonomies. In contrast with this view, the revised Piagetian approach advocated in this paper proposes that a general cognitive advance (operativity) makes possible both a conceptual advance (superordinate categories) and certain linguistic advances, such as an appreciation of hyponymic relations. These alternative accounts of the acquisition of superordinate categories entail different predictions under appropriate experimental conditions. Thus a general finding of differences in superordinate categorization between age-equivalent preoperational and concreteoperational groups would favor the Piagetian account because there is no clear basis within the language-based account for predicting such differences. As the result of a greater dominance of cognition by figurative relations, preoperational children should be limited relative to concrete-operational children in the employment of superordinate categories as effective or-

338

RICCO

AND

BEILIN

ganizations. Specifically, cognitive level effects should be evident where superordinate taxonomic relations must be established with less typical exemplars. Consistent with this prediction, preoperational subjects have been found to respond on a taxonomic basis significantly less often than chance and significantly less often than concrete-operational subjects on oddity, sort, and category membership tasks employing atypical exemplars of superordinate artifact categories. These cognitive level effects were absent or attenuated when purely typical superordinate exemplars were employed (Ricco, 1989). In addition to cognitive level effects on specific categorization tasks, a second prediction following from the alleged role of operational thought in superordinate category acquisition and explored in the present study is that preoperational subjects should be less stable or consistent than concrete-operational subjects in performance UC~OSScategorization tasks employing categories at this level of abstraction (Alexander & Enns, 1988; Piaget, 1951, pp. 273-291). The previous research establishing cognitive level effects (Ricco, 1989) did not relate the subject’s category membership decisions for a given category to her oddity or sort responses for that category.

If operativity facilitates the independence of taxonomic (e.g., intracategorical) relations from figurative relations, then for the operational child, an appreciation that two objects are exemplars of the same superordinate category, as evidenced on a Category Membership Task, should be a necessary and sufficient condition for categorizing those objects together on a subsequent Sample-Match task (offering both taxonomic and nontaxonomic response alternatives), regardless of the degree of figurative similarity between the objects, i.e., regardless of the typicality of the objects as category exemplars. For the preoperational child, however, recognition that these objects belong to the same category might be necessary but not sujjkient for taxonomic responding on the Sample-Match task. Also necessary should be figurative salience, as obtains between two typical exemplars of a category. Thus for less typical exemplars, exemplars sharing few figurative similarities with other category exemplars, the sample-match performance of preoperational subjects may contradict their previous category membership judgments. Concerning the category membership judgments themselves, preoperational subjects should exclude more atypical exemplars from their categories than do concrete-operational subjects. These predictions were explored in the present study by presenting ageand grade-equivalent preoperational and concrete-operational groups of children with category membership and Sample-Match Categorization Tasks employing color drawings of familiar exemplars of the artifact superordinate categories furniture, clothing, tool, toy, and vehicle. Findings that artifact categories are more graded and afford less agreement as to

SUPERORDINATE

CATEGORIZATION

339

their membership than natural kinds (Barr & Caplan, 1987). suggest that an emergent organizational competence such as operativity might be particularly relevant to the coherence of artifacts. Another purpose of the present study was to explore the extent of any cognitive level effects obtained by testing the fate of these effects across varying task conditions. Earlier research suggests that preschool deficits in taxonomic responding relative to older children can be attenuated through training or additional trials (Smiley & Brown, 1979; Tversky, 1985). In the present study multiple trials were employed on the SampleMatch Task to manipulate, conjointly, task familiarity and either the number or salience of competing response alternatives. The central question addressed by this exploratory manipulation was whether, and to what extent, trial 1 cognitive level effects would be manifest on subsequent trials. In addition, the more optimal conditions for taxonomic responding provided by trial 2, and especially trial 3, allowed a comparison of preoperational and concrete-operational subjects on an ability to discern difficult or problematic conceptual relations. namely, relations between exemplars not included under the same category by the subject on the category membership task. METHOD Subjects

Subjects consisted of 83 first graders (39 males, 44 females) attending St. Bartholomew’s School of Northeast Philadelphia and 12 first graders (6 males, 6 females) attending Fairmount Public School of Hackensack, New Jersey. Participants were white and came predominantly from lower middle-class to upper middle-class homes. On the basis of an Operativity Assessment consisting of conservation and seriation tasks, 20 first graders (10 males, 10 females) were identified as preoperational (mean age=6 years, 9 months; SD = 0.53) and 20 first graders (10 males, 10 females) were identified as concrete operational (mean age= 6 years, 8 months; SD = 0.31). The equivalent numbers of males and females both within and across groups occurred by chance and was not the result of any sampling constraint. Three of the preoperational subjects and three of the concrete-operational subjects came from the Fairmount School sample. The preoperational and concrete-operational groups did not differ significantly in age, t(38) = 0.42. Procedure

Testing was conducted in three sessions. In the first session all subjects received the Conservation of Number, Conservation of Length, and Seriation tasks composing the Operativity Assessment. The order of presentation for these tasks was randomized within and across subjects.

340

KICCO

AND

BEILIN

As a result of the Operativity Assessment, subjects were placed in a preoperational, concrete operational, or transitional group. Subjects assigned to the transitional group did not participate further in the study. Preoperational and concrete operational subjects returned in 2 to 10 days for a second test session in which they were administered the Category Membership Task. In 1 to 2 weeks, these same subjects returned for a third and final test session in which they were presented with the SampleMatch Task. Since the length of time between test sessions could not be held constant for all subjects, preoperational and concrete-operational subjects were matched for length of time between the second and third test sessions. Operativity assessment. The Conservation of Number. Conservation of Length, and Seriation Tasks were administered in accordance with a standard procedure described in O’Connor and Beilin (1980). Scoring criteria for the operativity assessment were adopted from Inhelder, Sinclair, and Bovet (1974). In order to pass a given trial of a conservation task, a subject had to provide both a correct conservation response and an adequate justification (identity, reversibility, compensation). Subjects who gave a correct conservation response but failed to justify it adequately, or who reversed their judgment, were scored as intermediate on that trial. On the Seriation Task, a subject was passed on trial 1 if the sticks were grouped in the correct order with even bases and on trial 2 if the subject selected the sticks for presentation to the experimenter in the correct order. All other outcomes were equivalently scored as failing. The three tasks. each with two trials, yielded a total of six trials. Subjects were scored as preoperational if they failed at least five of the six trials. Subjects were scored as concrete operational if they passed at least five of the trials. Cutegory Membership Tusk. The extensions of the superordinate categories clothing, furniture, tool, toy, and vehicle were assessed on the Category Membership Task. For each category, subjects were presented with a series of exemplars covering the full range of typicality for that category. Eight exemplars were presented for the vehicle category and 13 exemplars were presented for each of the other categories. In addition to category exemplars, the series of items for each category included 3 noncategory exemplars, e.g., umbrella, toothbrush, and eyeglasses for the category clothing (see Table 1 for the category exemplars). Stimuli consisted of 10 x lo-cm color drawings. For each category the items were laid out before the subject in a loose arrangement. The experimenter pointed to each item in turn. naming the object portrayed and asking the subject whether or not it belonged to the category at issue. The order of category presentation, the order of item arrangement before the subject, and the order of item presentation within a category were randomized both within and across subjects.

SUPERORDINATE

TABLE CATEGORIES

Clothing Skirt T-shirt Dress Robe Pajamas Pants Gloves Necktie Hat Scarf Apron Shoes Earmuffs Norr. Exemplars to least typical.

AND

EXEMPLARS

EMPLOYED

Furniture

are rank

1 ON THE CATEGORY

Tool

Couch Table Chair Bed Rocking chair Stool Bench Cabinet Clock Shelves Lamp Television Mirror ordered

341

CATEGORIZATION

Screwdriver Hammer Saw Drill Scissors Shovel Paint brush Lawnmower Rake R&X Ladder Pencil Broom within

a category

MEMBERSHIP

Vehicle

TOY Yo-yo Jack-in-box TOP Ball Kite Tricycle Bicycle Swing Color book Balloon Crayon Baseball bat Bowling pin by degree

TASK

of typicality,

Truck Car BUS

Motorcycle Train Airplane Ship Rocket Bicycle Tricycle Rowboat Raft

from

most

Sample-Match Tusk. On the Sample-Match Task the probability of selecting a taxonomic similarity (two exemplars of the same category) over alternative nontaxonomic, figurative similarities was assessed as a function of exemplar typicality and the scope or inclusiveness of a given subject’s category. Stimuli again consisted of 10 x lo-cm color drawings, including some of those employed on the Category Membership Task. First-grade familiarity with all task stimuli was established in two previous studies (Ricco, 1987, 1989). Each task item featured four pictures: one sample (e.g., t-shirt) and three matches (e.g., dress, flag, iron). Each sample-match combination constituted a qualitatively distinct similarity. These were taxonomic, perceptual, and thematic. Only the taxonomic match (e.g., dress) belonged to the same taxonomic category as the sample. The perceptual match (e.g., flag) bore a similarity of shape, size, color, and orientation to the sample. The thematic match (e.g., iron) was closely associated with the sample in some familiar event context. Table 2 presents the perceptual and thematic matches employed on the SampleMatch Task. No two items presented to a given subject featured the same perceptual or thematic match. There were three item types, determined by the nature of the taxonomic match. In each item type the sample was a typical exemplar (e.g., t-shirt) of a taxonomic category (clothing) and had been included in that category by the subject at issue. On two item types the taxonomic match had been included in the sample category by the subject and was either a typical exemplar (typical items), e.g., dress, or an atypical exemplar (atypicalinclusive items), e.g., shoes, of the sample category. A third item type

342

KICCO AND BEILIN TABLE PERCEPTUAL

AND THEMATIC

SIMILARITIES

2

EMPLOYED

ON THE SAMPLE-MATCH

TASK

Sample and Match Category

Sample

Perceptual

Thematic

Clothing

Robe T-shirt Chair Table Hammer Screwdriver Y o-y0 Jack-in-box Car Truck

Curtain Flag Jack-in-box Box carton Umbrella Toothbrush Clock Chair Panther Dinosaur

Hanger Iron

Furniture Tool Toy Vehicle

SZlW

Knife-plate-fork Board Hooks Hand Shelves Gas pump Koad

(atypical-exclusive items) featured a taxonomic match which was both an atypical exemplar of the sample category and had been excluded from the sample category by the subject. It was expected that concrete-operational children would select the taxonomic match significantly more often than chance on both the typical and atypical-inclusive items, items where they considered the match to be a member of the sample category, but not on the atypical-exclusive items. Preoperational subjects, however, were expected to select the taxonomic match more often than chance on the typical items only. There were three items of each type. This yielded a total of nine items. No taxonomic category was featured more than twice across the nine items. In addition, no two items of a given item type featured the same taxonomic category. The typical items for a given subject were otherwise randomly selected from a pool of items representing all five taxonomic categories. The taxonomic matches of the atypical-inclusive and atypicalexclusive items were, in the first case, the three least typical exemplars for which an inclusive response was made by the subject on the Category Membership Task and, in the second case, the three least typical exemplars for which an exclusive response was made. This insured that the taxonomic pairings of the atypical-inclusive items would be low in figurative similarity and that the taxonomic pairings of the atypical-exclusive items would represent difficult semantic relations for first graders. Exemplar typicality was determined on the basis of adult category membership norms established in a previous study (Ricco, 1987). These norms provide a measure of an exemplar’s degree of membership in a category by establishing the percentage of an adult sample including that exemplar in the category. In Table 1 all superordinate category exemplars employed in the present study are listed under their appropriate category in order

SUPERORDINATE

CATEGORIZATION

343

of typicality from most to least typical. As a check on the assumption that adult typicality norms reflect the perceptions of subjects in the present study, similar norms were established post hoc for preoperational and concrete-operational subjects based on the Category Membership Task administered in session two. Atypical exemplars were excluded from their category by from 41 to 85% of the present sample (Mean = 54%) while typical exemplars had a percentage of exclusion of 0 to 12% (Mean = 2.2%). Each task item was presented to the subject in an asymmetrical array, with the sample placed alone to the subject’s left and the three matches arranged in a column to the right of the subject. The positions of the three matches (taxonomic, perceptual, thematic) were randomized both within subjects (across items) and across subjects. The Sample-Match Task involved two trials, with the possibility of a third trial depending upon the subject’s responses on trials 1 and 2. On each trial and for each item, subjects were asked to justify their choice. On trial 1 the subject was instructed to select that match which is “the same kind of thing” as the sample. Following the subject’s selection of a match on trial 1, the chosen picture was removed and the remaining two matches were adjusted in their vertical arrangement so as to be equal distance from the sample. The subject was then told that although neither of the remaining alternatives was, in the subject’s opinion, as good a choice as the subject’s response on trial 1, one of the alternatives was better than the other as a match for the sample. The subject was asked to select the “better match.” For a given item, if the subject did not select the taxonomic match on either trials 1 or 2, that item was presented for a third trial following completion of trials 1 and 2 for all nine items. For the third trial the sample and taxonomic match were combined with a third picture bearing a purely anomalous relation (i.e., neither a figurative nor a nonfigurative similarity) to the sample and taxonomic match, thus providing an optimal setting for discrimination of the taxonomic relation. The three pictures composing trial 3 for an item were presented in the form of a triangular array. The positions of the three stimulus types (sample, match, and anomalous pictures) were randomized within and across subjects. Subjects were instructed to find the two pictures that are the same kind of thing. Before allowing the subject to respond, the experimenter named each picture and pointed out the three possible pairings. RESULTS Category Membership Task

The category membership decisions of preoperational and concreteoperational subjects were compared through a Cognitive Level (2) x Category (5) x Sex (2) analysis of variance on the percentage of exemplars

344

RICCO

AND TABLE

MEAN

PERCENTAGE”

OF EXEMPL.ARS

EXCLUDED

BY COGNITIVE

LEVEL

BEILIN 3 ON .THF. CAXGORY AND

MEMBERSHIP

TASK

CATEGORY

Category Cognitive Level Preoperational Concrete operational

Clothing

Furniture

Tool

Toy

Vehicle

18.1 (13.7) 9.2 (10.8)

35.0 (23.7) 33.1 (16.‘))

46.9 (22.0) 46.5 (21.0)

14.2 (17.0) 23.x (20.4)

22.5 (20.9) 23.8 (22.2)

Note. Numbers in parentheses are standard deviations. ’ There were 8 exemplars in the Vehicle cateogy and categories.

I3 exemplars

m each of the other

excluded from a category. The only repeated measure was Category. Percentages were used, rather than raw scores, because the categories do not contain equal numbers of exemplars. The main effect for Sex and the interactions involving Sex did not approach significance (F values approximated 1.00). The Cognitive Level x Category means are shown in Table 3. The cognitive levels did not differ significantly in their category membership decisions. Neither the Cognitive Level main effect, F( 1, 36) < 1.00, nor the Cognitive Level x Category interaction, F(4, 144) = 1.37, p < .25, were significant. Sample-Match Task To determine whether taxonomic responding was at above chance levels on trial 1, t tests for the significance of a single mean were computed on the number of taxonomic matches selected by preoperational and concrete operational subjects on each item type. There were six analyses, one for each Cognitive Level (2) x Item Type (3) combination. Because there are three response alternatives on trial 1 (taxonomic, perceptual, thematic) the appropriate chance value for these analyses is 0.33. With three items per item type, the mean number of taxonomic matches expected by chance (u) is 1.00 for the analyses. Means are shown in Table 4. Preoperational taxonomic responding was above chance on the typical items, t( 19) = 5.16, p < .OOl, but not the atypical-inclusive items, t(19) = -0.24, and was significantly below chance on the atypical-exclusive items, t(19) = -2.35, p < .05. Concrete-operational taxonomic responding was above chance on the typical items, t( 19) = 11.48, p < .OOl, and atypical-inclusive items, t(19) = 4.50, p < .OOl, but not the atypicalexclusive items, t(19) = - 1.08. To determine whether taxonomic responding on trial 2 alone was above chance a unique expected number of taxonomic responses on trial 2 was

SUPERORDINATE

MEAN

NUMBER’

OF TAXONOMIC

MATCHES

CATEGORIZATION TABLE 4 ON TRIAL 1 BY COGNITIVE Item

Cognitive Level Prcoperational Concrete operational Note. Numbers in parentheses ” Maximum score = 3.0.

34.5

LEVEL AND I.TEM TYPF.

Type

Typical

Atypical Inclusive

Atypical Exclusive

1.95 (0.83) 2.55 (0.61)

0.95 (O.Y5) I.95 (O.YS)

0.65 (0.67) 0.80 (0.83)

are standard

deviations.

computed for each subject based upon the number of items for which a taxonomic match was not made on trial 1. Since there are two response alternatives on trial 2, a 0.50 chance value was used in computing the expected values. For example, if a given subject failed to select the taxonomic match on two of the three typical items on trial 1, then that subject’s expected value for trial 2 responding on this item type was 1.00 (i.e., 0.50 x 2.00). The unique expected values for a given cognitive level on a given item type were then summed and averaged to obtain a mean expected value for that analysis. Preoperational taxonomic responding continued at chance levels on trial 2 for both the atypical-inclusive (M = 1.28; SD = 0.75; u = 1.14), t(17) = 0.79, and atypical-exclusive items (M = 1.35; SD = 0.93; U= 1.18). t(19) = 0.84. Likewise, concreteoperational responding on the atypical-exclusive items also failed to reach significance on trial 2 (M = 1.26; SD = 0.81; u = 1.16), t(l8) = 0.56. To directly compare concrete-operational and preoperational subjects, a Cognitive Level (2) x Item Type (3) x Sex (2) analysis of variance with one repeated measure (Item Type) was computed on the number of taxonomic matches made on the first trial of the Sample-Match Task (see Table 4 for the relevant cell means). There were no significant effects involving Sex (F values approximated 1.00). Both the Cognitive Level, F( 1, 36) = 10.97, p < .002, and the Item Type, F(2, 72) = 43.19, p < ,001, main effects were significant. In addition, the Cognitive Level x Item Type interaction was significant, F(2, 72) = 3.36, p < .04. An analysis of Cognitive Level at each Item Type yielded significant simple main effects of Cognitive Level for the typical items, F(1, 100) = 5.38, p < .05, and the atypical-inclusive items, F(1, 100) = 14.95, p < .Ol. The cognitive levels did not differ on the atypical-exclusive items, F(1, 100) < 1.00. For the typical and atypical-inclusive items only, concreteoperational subjects made significantly more taxonomic matches than preoperational subjects.

346

RICCO AND BEILIN TABLE

MEAN

NUMBER’

OF TAXONOMIC

5

MATCHES ON TRIAL.S 1 AND 2 w COGN~TIVB TYPE, AND SEX

LEVEI..

ITEM

Item Type Cognitive Level Preoperational Concrete operational Preoperational Concrete operational

Typical

Atypical Inclusive

Atypical Exclusive

2.50 (0.71) 3.00 (0.00)

Boys 2.30 (0.68) 2.50 (0.53)

2.20 (0.79) 1.70 ( 1.M)

2.X0 (0.42) 3.00 (0.00)

Girls I .90 (0.74) 7.90 (0.32)

I.XO (0.79) 2.30 (0.82)

Note. Numbers in parentheses are standard deviations. ” Maximum score = 3.00.

Preoperational and concrete-operational subjects were more comparable in their taxonomic responding by trial 2 as indicated by a Cognitive Level (2) x Item Type (2) x Sex (2) analysis of variance on the mean number of taxonomic matches across trials 1 and 2. The typical items could not be included in this analysis because concrete operational subjects achieved perfect scores by trial 2. Cell means are shown in Table 5. Neither the Cognitive Level, F(1, 36) = 2.98, p < .lO, nor the Cognitive Level x Item Type interaction F(1, 36) = 3.62, p < .065, were significant, though the latter approached significance. The Cognitive Level x Sex interaction, F(1, 36) = 6.66, p < .02, was significant. All other effects involving Sex were not significant (F values < 1.00). An analysis of Cognitive Level for each sex yielded a significant simple main effect of Cognitive Level for girls. F(1. 36) = 4.61, p < .05, but not for boys, F(1, 36) < 1.00. Although the Cognitive Level x Sex interaction across trials 1 and 2 indicates some persistance of cognitive level differences from trial 1, these differences are, in general, significantly attenuated by trial 2. On item types where taxonomic responding across trials 1 and 2 was not above chance, i.e., the atypical-inclusive items for preoperational subjects and the atypical-exclusive items for subjects of both cognitive levels, would subjects select the taxonomic match under the optimal conditions of trial 3, where the only competing response alternatives are anomalous relations? To determine whether taxonomic responding on trial 3 alone was above chance, t tests for the significance of a single mean

SUPERORDINATE

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347

were computed on the mean number of taxonomic responses, As in the analysis of trial 2 responses, a unique expected number of taxonomic responses on trial 3 was calculated for each subject based upon the number of items for which a taxonomic response was not made on trials 1 or 2. There are three response alternatives on the oddity task format of trial 3. Therefore a 0.33 chance value was employed in calculating the expected values. Concrete-operational taxonomic responding on trial 3 for the atypicalexclusive items was above chance (M = 1.08; SD = 0.67; u = 0.55), t(l1) = 2.63, p < .05. Preoperational subjects did not select the taxonomic pair significantly more often than chance for either the atypical-exclusive items (M = 0.80; SD = 0.68; u = 0.44), t(14) = 2.06, p < .065, or the atypical-inclusive items, (M = 0.71; SD = 0.73; u = 0.42), t(13) = 1.52, p < .17. When trial 3 responding is examined without regard for item type, i.e., collapsing across item type, taxonomic responding is above chance for both preoperational (M = 1.56; SD = 1.04; u = 0.83), t(17) = 2.98, p < .Ol, and concrete operational (M = 1.38; SD = 0.87; u = 0.66), t(12) = 3.00, p < .02 subjects. Thus, the addition of trial 3 responses for the typical items raised preoperational trial 3 taxonomic responding above chance levels. To what extent can subjects articulate the semantic relation between taxonomic pair members and how do the cognitive levels compare in this regard? Subject justifications for taxonomic responseswere scored by two independent judges on the basis of two familiar dimensions of semantic organization. A given justification was scored as necessary if it mentioned at least one property shared by both taxonomic pair members and necessary to the taxonomic category at issue, i.e., a property which, in the estimation of the judges, must be possessed by any exemplar of the category. A justification was scored as eliminative if it mentioned at least one property shared by both taxonomic pair members and not possessed by any of the other objects from which the subject was choosing on any of the trials for that item. Finally, a justification was scored as necessary and eliminative if it contained at least one shared property meeting both of the above criteria. Individual justifications could be scored into more than one of the three categories. Separate interjudge reliabilities were computed for the necessary (93.5%), eliminative (87.6%), and necessary and eliminative (90.1%) categories. Disagreements between judges in scoring were resolved through discussion. For each of the three scoring categories (necessary, eliminative, and necessary and eliminative) a separate Cognitive Level (2) x Item Type (3) x Sex (2) analysis of variance was computed on the percentage of taxonomic response justifications (across all three trials) meeting the criteria of the scoring category at issue (see Table 6 for cell means). One preoperational subject was omitted from the analysis because he did not

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TABLE 6 PERCENTAGE OF NECESSARY, EIJMINATIVE. AND NECESSARY AND EL.IMINAIIVE JUSTIFICATIONS BY ITEM TYPE AND COGNI.TIVE LEVEL. Item

Cognitive Level

Type

Typical

Atypical Inclusive

Preoperational Concrete operational

64.S

Necessary 53.2

Preoperational Concrete operational

Xl.3

71.3

91.6

Now.

N = for preoperational

60. 1 6X.0 subjects.

35.X

x3.1

Necessary Preoperational Concrete operational

Atypical Exclusive

5x.2

Eliminative 63.0

37.5

79.8

hl.S

and eliminative 37.2

32.3

73.1 N = 20 for concrete

4x.7 operational

subjects.

make any taxonomic responses to the atypical-exclusive items. Results indicated that concrete-operational subjects gave a greater percentage of necessary justifications, F(1, 35) = 7.24, p < .Oll, eliminative justifications, F(1, 35) = 5.41, p < .026, and necessary and eliminative justifications, F(1, 35) = 5.01, p < .032. than preoperational subjects. The Cognitive Level x Item Type interaction did not reach significance in any of these analyses, F(2, 70) = 1.55 for the necessary justifications; F(2, 70) < 1.00 for each of the other scoring categories. Thus the greater articulation of the semantic relation by concrete-operational subjects held for each item type. No effects involving Sex were significant across these analyses. The largest F value obtained in this regard was for the Sex main effect on the necessary and eliminative justifications, F(L. 35) = 2.83, p < .lO. DISCUSSION The present study sought to extend previous findings (Ricco, 1989) suggesting a link between operativity and the acquisition of superordinate categories. Superordinate categorization requires an appreciation of taxonomic relations involving figurative dissimilarity. Operativity has been implicated as a general competence of this kind (Gold, 1987, pp. 7-15). In the present study it was hypothesized that concrete-operational subjects would show greater stability or consistency across superordinate categorizations than preoperational subjects. This general hypothesis was con-

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firmed. For concrete operational subjects, the inclusion of two exemplars under the same superordinate category on the Category Membership Task was necessary and sufficient for subsequent selection as a taxonomic pairing on the Sample-Match Task, regardless of exemplar typicality. Thus taxonomic responding by concrete-operational subjects on the SampleMatch Task was above chance for both the typical items and the atypicalinclusive items, and did not differ from chance on the atypical-exclusive items. For preoperational subjects, co-inclusion under the same superordinate category was necessary but not sufficient for taxonomic responding on the sample-Match Task. An additional necessary condition for preoperational taxonomic responding was the typicality of the taxonomic match. Thus preoperational taxonomic responding on the Sample-Match Task was above chance for the typical items only. The greater consistency across categorization tasks exhibited by concrete-operational subjects relative to preoperational subjects was accompanied by a greater selection of taxonomic matches on the typical and atypical-inclusive items on the Sample-Match Task. Despite confirmation of the general hypothesis, the results of the present study failed to replicate a previous finding. In an earlier study (Ricco, 1989)) preoperational category membership decisions for the categories clothing and furniture, the only two categories tested, were found to be more conservative than concrete-operational decisions, specifically concerning atypical exemplars. In the present study, however, preoperational and concrete-operational subjects did not differ in their membership decisions for any of five superordinate categories, including clothing and furniture. This failure to replicate the category membership finding raises the possibility that the various cognitive level effects obtained in the present and previous studies might reflect a difference between preoperational and concrete-operational subjects in the utilization of superordinate knowledge on specific tasks rather than a difference in superordinate knowledge per se. By operationally defining taxonomic pairings on the Sample-Match Task on the basis of the subject’s category membership decisions, the present study tested a general ability to utilize existing superordinate knowledge. Cognitive level effects were in evidence in regard to this ability. On the other hand, the Category Membership Task, on which no cognitive level effects were present, is a gross index of superordinate knowledge itself, specifically category inclusiveness or extension. If operativity is implicated in the utilization, but not the acquisition, of superordinate natural categories, then the importance of operativity to superordinate categorization might not lie in the appreciation of taxonomic relations involving figurative dissimilarity. Such relations might be available to preoperational subjects. Operativity could facilitate utilization of superordinate knowledge by fostering a decentering of attention from

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salient perceptual or thematic similarities which, if present in a set of stimuli, could interfere with the construction of semantic relations among the stimuli. In addition, operativity might facilitate utilization by enabling a recognition of the superiority of taxonomic organization over alternative, figurative bases. Viewing the role of operativity in superordinate categorization as one of utilization remains consistent with Piaget’s account of development as a progressive differentiation of cognition from figurative functions (Gold, 1987, pp. 70-71). Also, implicating operativity in the utilization of knowledge is consistent with a Neo-Piagetian interpretation of operativity as a lifting of constraints on information processing capacity or efficiency (Case, 1985, p. 422; Pascual-Leone & Smith, 1969). From within Pascual-Leone’s account of development. one direct outcome of a domain-general increase in mental capacity is more effective boosting of or task-relevant schemes (e.g., taxonomic categories) and inhibition suppression of task-irrelevant schemes (e.g., figurative representations) (Johnson, Fabian, & Pascual-Leone, 1989; Pascual-Leone, 1987). In addition, the adoption by several Neo-Piagetian theorists of the figurativeoperative distinction suggests that Neo-Piagetian theories (Case, 1987; Pascual-Leone, 1987) might provide an effective alternative characterization of domain-general change in the utilization of taxonomic knowledge. A contention that preoperational limitations reside in the utilization or implementation of a taxonomic competence, rather than in the existence of that competence per se. receives additional support from the results of the present study. Some of the disparities between preoperational and concrete-operational performance were limited to trial 1. By the second trial of the Sample-Match Task, the number of taxonomic matches selected by preoperational subjects was comparable to that of concreteoperational subjects. Thus there is some indication that preoperational taxonomic responding can increase as a result of task familiarity, practice, or a reduced array of competing response alternatives. Nontheless, the bulk of the trial 2 and 3 results suggest that preoperational and concrete-operational subjects differ in a general competence to appreciate taxonomic relations involving figurative dissimilarity. Prcoperational taxonomic responding continued at chance levels for both the atypical-inclusive and atypical-exclusive items on each of trials 2 and 3. Fatigue is not a likely explanation of these results because preoperational taxonomic responding was above chance on trial 3 for the typical items. Concrete operational taxonomic responding was above chance on trial 3 for each of the item types, indicating that concrete-operational subjects could discern the problematic taxonomic relation of the atypical-exclusive items under the ideal conditions of trial 3. The justification data further support the contention that operativity is implicated in the appreciation

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of superordinate semantic relations and therefore in the acquisition of superordinate categories. In providing justifications for their taxonomic responses on the Sample-Match Task, concrete-operational subjects were able to articulate the taxonomic relation to a greater extent than preoperational subjects by making greater reference to properties necessary to the category at issue and by providing rationales for their taxonomic selection which specifically excluded the alternative responses. The purely correlational nature of the present study must qualify any conclusion that differences between preoperational and concrete-operational subjects represent developmentally based, cognitive differences, whether in the acquisition or merely the utilization of superordinate representations. In particular, the absence of any control on verbal IQ raises the possibility that concrete and preoperational subjects differed on some general and nondevelopmental verbal ability. It is not clear, however. that partialing out or covarying a verbal IQ measure would have been appropriate in this study. The statistical control of IQ is problematic because implicit in the hypotheses at issue in this study is a claim that the emergence of operativity will have an impact upon verbal intelligence. One strength of the present design is the control of age and grade. Age/grade is an index of several variables previously linked to the acquisition of superordinates and which might otherwise constitute alternative accounts of the present findings. These include: (a) knowledge base (Carey, 1985), (b) the operation of a general learning procedure which is not itself subject to development (Nelson, 1985; Rosch & Mervis. 1975), (c) theory or model change, i.e., domain-or content-specific reorganization of knowledge (Carey, 1985; Gelman & Markman, 1986), and (d) the effects of language development in general, and semantic development in particular, on conceptual development (Benelli, 1988: Markman. 19X7, 1990; Nelson, 1985). The general finding that figurative properties of category exemplars influence the categorizations of preoperational children but not those of concrete-operational children is consistent with, and predicted by, both Piagetian and Neo-Piagetian, domain-general accounts of cognitive dcvelopment (Case, 1987; Gold, 1987, pp. 7-15). Domain-specific accounts of category acquisition (e.g., Carey, lYX5, pp. 194-201; Keil, 19X7), stressing the embedding of categories in naive theories or cognitive models, cannot readily explain why a measure of conservation or seriation should be related to the categorization of artifacts. In explaining theory or model change, domain-specific accounts appeal, primarily, to increases in knowledge base, while downplaying domain-general facets of development such as emergent logical organization or increases in information processing capacity (Carey. 1985, pp. 181--X1; Medin & Wattenmaker, 1987). The fact that research supporting a domain-specific account typicalfy fails to

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control for age leaves open the possibility that domain-general change may drive both theory or model change and change in conceptual development . Language-based accounts of superordinate category acquisition (Markman, 1990; Nelson, 1985) are hard pressed to explain systematic differences in categorization performance between age-and grade-equivalent groups. where the latter are established through a presumably cognitive variable. This is particularly true for the present findings where cognitive level effects are tied to relations of figurative similarity and dissimilarity among category exemplars. It is a central claim of language-based accounts that an appreciation of the independence of superordinate taxonomic relations from figurative similarity is primarily motivated by semantic development rather than cognitive development (Nelson, 1985, pp. 15% 159). The present and previous findings (Ricco, 1989) suggest that superordinate categorization has an emergent and domain-general component to it. Operativity is one possible formulation of such a component. Whether the specific role of operativity in superordinate categorization resides in the acquisition of category representations or in the utilization of knowledge inherent in category representations cannot currently be determined. The present findings extend previous research by providing additional support for the relevance of operativity to acquisition while suggesting the utilization hypothesis. A more accurate picture must await further research. REFERENCES Alexander. Child

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