Is the most representative skunk the average or the stinkiest? Developmental changes in representations of biological categories

Abstract

People often think of categories in terms of their most representative examples (e.g., robin for BIRD). Thus, determining which exemplars are most representative is a fundamental cognitive process that shapes how people use concepts to navigate the world. The present studies (N = 669; ages 5 years - adulthood) revealed developmental change in this important component of cognition. Studies 1-2 found that young children view exemplars with extreme values of characteristic features (e.g., the very fastest cheetah) as most representative of familiar biological categories; the tendency to view average exemplars in this manner (e.g., the average-speeded cheetah) emerged slowly across age. Study 3 examined the mechanisms underlying these judgments, and found that participants of all ages viewed extreme exemplars as representative of novel animal categories when they learned that the variable features fulfilled category-specific adaptive needs, but not otherwise. Implications for developmental changes in conceptual structure and biological reasoning are discussed.

Keywords: Biological reasoning; Conceptual development; Ideals.

Fig. 1.

In Study 1, all participants saw illustrations of familiar animal kinds (cheetahs, elephants, porcupines, giraffes, skunks, kangaroos, sharks, and lions), one at a time, each as a scale of five exemplars ranging from least to most extreme on a characteristic adaptive feature (e.g., faster cheetahs, stinkier skunks; top panel). We described variability in the relevant property (e.g., “This cheetah runs the fastest, this cheetah runs the slowest, and this cheetah is in the middle, it runs faster than some cheetahs and slower than some other cheetahs.”) In the testing phase, participants in the Best condition gave a prize to the “best” exemplar (lower-left panel); participants in the Representative condition chose an exemplar to put in the book to teach a novice (a puppet named “Feppy” for children, “the stranger” for adults) about the category (lower-center panel). Participants in both conditions then completed a forced-choice induction question about each animal kind (lower-right panel) in which they heard that the most extreme exemplar had one unfamiliar property while the average exemplar had a different one; they chose which of the two properties another member of the kind would have. Study 2 used the same method as Study 1 except that a different prompt was used for the Representative condition, with participants asked to select the “real, cheetah-y cheetah.”

Fig. 2.

Average exemplar selected (as the best or most representative) in Study 1 (N = 152), by age group and condition. Higher values represent exemplars that are more extreme on a characteristic adaptive property (e.g., faster cheetahs, stinkier skunks) across all eight animal trials. Exemplar 3 represents selecting the animal in the middle of the scale. Large shapes represent group means by age group and condition; error bars show 95% Confidence Intervals. Small lines are responses to individual trials.

Fig. 3.

Average exemplar selected (as the best or most representative) in Study 2 (N = 211), by age group and condition. Higher values represent exemplars that are more extreme on a characteristic adaptive property (e.g., faster cheetahs, stinkier skunks) across all eight animal trials. Exemplar 3 represents selecting the animal in the middle of the scale. Large shapes represent group means by age group and condition; error bars show 95% Confidence Intervals. Small lines are responses to individual trials.

Fig. 4.

In Study 3, after completing a scale-training phase as in Studies 1 and 2, participants made representativeness and informativeness judgments about eight novel animals, one at a time, each presented as a scale of five exemplars ranging from least to most extreme on a single feature (e.g., snout length). Depending on condition in a 2 × 2 design, participants heard different types of information about each animal kind: functional information (given, not given), and contrast category information (present, not present). All participants then selected which exemplar was most representative (e.g., “the real, tulver-y tulver”) and which (of all five exemplars) was most informative about the category (e.g., “which should we look at to learn about tulvers?”). Responses were scored from 1 to 5, with higher numbers indicating exemplars that better met functional goals (when functional information was present) and lower numbers indicating exemplars that were more contrastive (when a contrast category was present).

Fig. 5.

Average exemplar selected, by age group and functional ideal information, collapsed across both levels of contrast category information (N = 296). Higher values represent more functionally valuable exemplars. Exemplar 3 represents selecting the animal in the middle of the scale. Large shapes are means by age group and condition across all eight trials; error bars show 95% Confidence Intervals. Small lines are responses to individual trials. The top graph shows representativeness responses (e.g., “which is the real, tulver-y tulver?”); the bottom graph shows informativeness responses (e.g., “which would you look at to learn about tulvers?”).