Date of Award


Degree Type


Degree Name

Doctor of Philosophy



Major Professor

Christopher H. Skinner

Committee Members

Robert L. Williams, William Calhoun, Thomas W. George


The primary purpose of this study is to extend research on increasing accuracy on academic assignments through use of the additive interspersal procedure. Additive interspersal is the addition of brief and/or easy problems among longer, more difficult target problems. Research has shown additive interspersal is effective in promoting student choice in regards to engaging in assignments. Only one study has found an increase in student accuracy on interspersed assignments as compared to control assignments when using additive interspersal. The current study attempted to determine if the results of that study are a statistical outlier or whether the uniqueness of that study using assignments requiring different task demands, can increase problem accuracy.

Students (N=52) from three fifth-grade classes completed six math assignments incorporating two task demands and three ratios of interspersal. The interspersal ratios applied were no interspersal, on interspersed problem per three target problems, and one interspersal problem per one target problem. Each of these three ratios was used in two task demands. In the written (low-attention) task, students completed problems via paper and pencil. In the oral (high-attention) task, students had to compute mathematics problems in their head.

Results showed students performed more accurately on written tasks compared to oral tasks. A target to interspersal problem ratio of 3:1 on oral tasks led to a significant increase in accuracy compared to the no interspersal and 1:1 interspersal conditions. A target problem to interspersed problem ratio of 1:1 on written tasks led to a significant increase in accuracy when compared to the no interspersal condition.

The results of this study suggest the interspersal procedure can be used to increase student accuracy in math. However, the most effective ratio of interspersal to target problems is dependent on task demands. Interspersal studies have shown mixed results regarding student accuracy on assignments under the additive interspersal procedure. Currently, there is no understanding of the causal mechanisms to explain why interspersal increases accuracy in some instances but has no effect in other instances. Future theoretical research that explains the causal mechanism(s) of the interspersal procedure may allow us to maximize its impact on performance.

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