A behavior-based circuit model of how outcome expectations organize learned behavior in larval Drosophila

Drosophila larvae combine a numerically simple brain, a correspondingly moderate behavioral complexity, and the availability of a rich toolbox for transgenic manipulation. This makes them attractive as a study case when trying to achieve a circuit-level understanding of behavior organization. From a series of behavioral experiments, we suggest a circuitry of chemosensory processing, odor-tastant memory trace formation, and the "decision" process to behaviorally express these memory traces--or not. The model incorporates statements about the neuronal organization of innate vs. conditioned chemosensory behavior, and the types of interaction between olfactory and gustatory pathways during the establishment as well as the behavioral expression of odor-tastant memory traces. It in particular suggests that innate olfactory behavior is responsive in nature, whereas conditioned olfactory behavior is captured better when seen as an action in pursuit of its outcome. It incorporates the available neuroanatomical and behavioral data and thus should be useful as scaffold for the ongoing investigations of the chemo-behavioral system in larval Drosophila.     

Assessing School Academic Productivity: The Case of Chicago School Reform

This paper considers the issues raised in using standardized achievement test scores for purposes of examining the academic productivity of schools. We critique some commonly used practices by urban school districts and suggest an alternative approach – the school productivity profile. This profile is based on an assessment of each school's contribution to student learning, or value-added, rather than just the overall level of student attainment. We illustrate, using 10-year achievement trend data from the Chicago Public Schools (CPS), both the problems with some commonly reported indicators of school effectiveness and the idea of a school productivity profile. While our analyses suggest broad-based improvements in student learning in many Chicago schools over the past 10 years, we also found that the current testing system is not well designed to make such judgments accurately. We conclude that extant standardized testing systems, like the ITBS used in Chicago, do not afford an accurate basis for assessing school productivity and how this might be changing over time. These results have important policy implications. As school districts seek to become more outcome oriented, they will need to invest in better testing and reporting systems in order to know whether they are making genuine progress in this regard.     

Describing the Acquisition of Determiners in English: A Growth Modeling Approach

This paper, based on naturalistic data, describes the acquisitional course and use of the articles a and the in young English-speaking children (18-61 months), with special emphasis on the role of individual variation. A growth modeling approach to the data reveals that children's individual acquisition schedules are similar in trend, but vary in the rate at which they omit determiners at a given point of time. This picture suggests that an analysis that presumes homogeneous development will seriously misrepresent the fluctuations between and within individuals. Interestingly, this variation does not reflect a variation in children's abilities to use determiners correctly-irrespective of the rate in which they used determiners, children seldom used determiners incorrectly. The analysis also reveals that children's optional omission of determiners in obligatory contexts, beginning at 18 months of age, gradually decreases on average by 3-4% a month until 36 months of age, and thereafter plunges by a factor of 10 to an average of 0.3% per month. At 36 month of age the majority of children use determiners at a near-mastery level (Brown, 1973). These findings provide a useful framework for theorizing about possible mechanisms underlying the nature of early language development pre- and post-36 months of age.