When people perceive themselves as similar to others, greater liking and closer relationships typically result. In the first randomized field experiment that leverages actual similarities to improve real-world relationships, we examined the affiliations between 315 9th grade students and their 25 teachers. Students in the treatment condition received feedback on 5 similarities that they shared with their teachers; each teacher received parallel feedback regarding about half of his or her 9th grade students. Five weeks after our intervention, those in the treatment conditions perceived greater similarity with their counterparts. Furthermore, when teachers received feedback about their similarities with specific students, they perceived better relationships with those students, and those students earned higher course grades. Exploratory analyses suggest that these effects are concentrated within relationships between teachers and their "underserved" students. This brief intervention appears to close the achievement gap at this school by over 60%.

Early studies examining seasonal variation in academic achievement inequality generally concluded that socioeconomic test score gaps grew more over the summer than the school year, suggesting schools served as “equalizers.” In this study, we analyze seasonal trends in socioeconomic status (SES) and racial/ethnic test score gaps using nationally representative data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010–2011 (ECLS-K:2011), which includes more school-year and summer rounds than previous national studies. We further examine how inequality dynamics are influenced by the operationalization of inequality. Findings are consistent with a story in which schools initially accelerate relatively lower-achieving groups’ learning more so than higher-achieving groups; however, this school-year equalizing is not consistently maintained and sometimes reverses. When operationalizing inequality as changes in relative position, the reversal of school-year equalizing is more pronounced.

There is considerable interest in comparative research on different species’ abilities to respond to human communicative cues such as gaze and pointing. It has been reported that some canines perform significantly better than monkeys and apes on tasks requiring the comprehension of either declarative or imperative pointing and these differences have been attributed to domestication in dogs. Here we tested a sample of chimpanzees on a task requiring comprehension of an imperative request and show that, though there are considerable individual differences, the performance by the apes rival those reported in pet dogs. We suggest that small differences in methodology can have a pronounced influence on performance on these types of tasks. We further suggest that basic differences in subject sampling, subject recruitment and rearing experiences have resulted in a skewed representation of canine abilities compared to those of monkeys and apes.

A method to excite and visualize transverse standing waves on a vibrating string with one or both ends free is described. A stretched coil extension spring serves as the flexible vibrating string. A free end is achieved by attaching one end to a long thin steel wire that stretches the spring and thus provides tension with a nearly inertia-free suspension. The apparatus can be used as a qualitative lecture demonstration or as a quantitative experiment where it can serve as an instructive example of the application of boundary conditions.