Publication Date


Document Type


First Advisor

Pillow, Bradford H.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Psychology


Science inquiry involves reasoning and drawing conclusions about properties or constructs that may not be directly observed and are not immediately verifiable. Prior scientific reasoning investigations have examined children’s reasoning about observable items and immediately verifiable conclusions. The current investigation examined children’s evaluations of the certainty of conclusions drawn from evidence when reasoning about both immediately observable properties and unobservable properties with the same task. Kindergarten, first grade, third grade, and adult participants (N = 70) were presented with an online experimental procedure. The procedure included two conditions (Observable vs. Unobservable) each involved reasoning about three levels of evidence (conclusive vs. inconclusive vs. guess). The Observable condition assessed participant’s ability to reason about observable properties using animated cues, and the Unobservable condition assessed children’s ability to reason about unobservable properties using animated cues. A 4×2×3 ANOVA (Age × Condition × Evidence Level) was conducted, with Age (kindergarten, first grade, third grade, adults) as a between-subjects factor and Condition (observable vs. unobservable) and Evidence Level (conclusive vs. inconclusive vs. guess) as within-subjects factors. For the Observable condition, the ANOVA revealed a significant effect of Evidence Level. Kindergarten children gave significantly higher certainty ratings for the conclusive compared to the inconclusive trials. In contrast, first graders, third graders, and adults, reported significantly higher certainty ratings for the conclusive trials compared to the inconclusive and conclusive trials compared to the guess trials. The Unobservable condition revealed a significant effect of Evidence Level and a significant Age × Evidence Level interaction. Kindergarten and first grade children demonstrated difficulty differentiating the three levels of evidence resulting in no significant differences. However, third grade children reported significantly higher certainty ratings for conclusive compared to inconclusive trials and adults reported significantly higher certainty ratings for conclusive compared to inconclusive trials and conclusive compared to guess items. Results indicate a difference in reasoning between observable and unobservable evidence across levels of evidence. By kindergarten, children can begin to distinguish different levels of evidence with certainty ratings when reasoning about observable properties. The comparison of the Unobservable condition demonstrated improved performance with age, it was not until third grade that children could successfully reason about unobservable properties. The participants’ certainty ratings suggest a progressive differentiation between levels of evidence with increased age, especially for the unobservable outcomes. The current investigation promotes greater understanding of the extent of abilities for scientific reasoning across age groups.


116 pages




Northern Illinois University

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