Published online by Cambridge University Press: 26 September 2008
Prior empirical work in semantic development has produced an impressive finding showing that children can reliably detect a modal's relative force (e.g. that must is stronger sounding than may) by five-and-a-half years of age. We investigate the extent to which a representation of relative force can account for an understanding of epistemic modals when their logical meaning is considered (i.e. when modals are interpretable as expressions of necessary and possible conclusions). Experiment 1 presents a replication of Hirst & Weil's hidden-object task, which originally included the supremely forceful indicative is. Thirty-two five-year-olds were required to find a peanut hidden under one of two containers based on a pair of statements that contrasted is with has to, has to with might, or is with might. Half the children were entitled to search for the peanut upon hearing the two statements and half were required to indicate only where they would look. Results largely confirmed the influence of relative force in this paradigm. Both groups of children usually searched under the container associated with the stronger-sounding term. Experiment 2 employed a modified version of the hidden-object task in which contrasts presented one true and one false modal statement and 32 five-year-olds, 20 seven-year-olds, 16 nine-year-olds and 20 adults were asked to determine which of two statements was correct. Half the contrasts presented a relatively weaker-sounding modal term in the true statement and the other half presented equally forceful modal terms in the two statements. No age group systematically endorsed a false stronger-sounding modal statement over a true weaker-sounding one. The five-year-olds' rate of correct responding overall was above levels predicted by chance. Mature logical modal understanding was found among seven-year-olds who routinely endorsed a contrast's true modal statement. These findings suggest that deductive inference is an early semantic component of modal terms.
This research was supported in part by grants from the National Institute of Mental Health (MH15755-14) and the National Institutes of Child Health and Human Development (T32 HD-07151 and HD-27376). Portions of this study were presented at the Jean Piaget Society Meeting in Chicago, June, 1994. The authors would like to express their gratitude to the late Martin Braine, to Bill Charlesworth, Karen Freeman, Michael Maratsos, Eric Reittinger, Dan Sperber, two anonymous reviewers, and Katharine Perera for their comments on various parts of this work, to Valerie Abel for help in piloting an early version of Experiment 2, to Ying-rui Yang for explicating certain issues concerning modal logic, and to the principals, teachers and students of the Friends School of Minneapolis, The Torah Academy and the Minneapolis Jewish Day School.