Discovered: We give up searching when targets are few and far between; studying the urban landscape; science teachers release invasive species into the wild; inside the brains of hoarders. 

How to stay on the hunt. If you're an airport security worker tasked with sniffing out weapons but you haven't found any dangerous items in months, staying motivated can be hard. The question of what keeps people looking for needles in a haystack is exactly what Duke University psychologists wanted to study. So they presented test subjects with a number of screens and asked them to pick out specific shapes embedded among a field of similar shapes. For some participants, there were lots of target items to find. For others, the target items were more elusive. Feedback after each screen showed them what they had missed. "Searchers who had found that there could be a lot of targets stayed on task longer," said researcher Matthew S. Cain. "Searchers who had fewer targets to find gave up on a given screen sooner." The findings bolster the researchers "satisfaction of search" theory, which claims that people are unlikely to find subsequent targets after finding a first one. They also theorize that searchers are prone to quitting after the first find when targets appear infrequently, while searchers who come across targets more often will stay with the hunt longer. [Duke]

Breaking down the visual data of cities. People who've lived in distinctive-looking cities can often recognize a city's landscape in even the most nondescript photographs of its unassuming side streets. Researchers from Carnegie Mellon and INRIA/Ecole Normale Supérieure teamed up to study on an atomic level the features that define cities. They created visual data-mining software that automatically detects and processes details like signs, street lamps, railings and other specific architectural designs from 40,000 Google Street View images of cities like Paris, London, New York, and Barcelona. "In the long run, we wish to automatically build a digital visual atlas of not only architectural but also natural geo-informative features for the entire planet," says CMU professor Alexei Efros. [Carnegie Mellon University]

Many science teachers to blame for invasive species. Introducing invasive species into an environment where they don't belong can drastically alter an ecosystem. Even though they're probably aware of this, many science teachers have been releasing invasive species into the wild. Sam Chan, an invasive species expert Oregon State University, conducted a study of science teachers who use live animals to illustrate instruction, and he found that only 10% of respondents participated in a planned release program. "We need to work through the whole chain and educate both the teachers and suppliers about the potential damages—both environmental and economic—that invasive species may trigger," says Chan. [Science Daily]

How hoarders' brains work. For people who don't feel a need to desperately cling to things, it can be hard to understand why those who suffer from hoarding disorder get so upset when their material possessions are threatened. David Tolin of Hartford Hospital and his colleagues used brain scans to better understand how hoarders react when trying to clean their homes. The scans showed strange activity in the anterior cingulate cortex and insula, regions that process the value of objects, assesses risks, and monitor unpleasant feelings. According to the National Institutes for Mental Health, these findings suggest that underlying issues such as "lack of self-insight, indecisiveness, sense that the wrong decision is being made, inflated estimates of the desirability of objects, and exaggerated perception of risk" are key to understanding hoarding disorder. [NIMH]