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Mass public shootings have generated significant levels of fear in the recent years, with many observers criticizing the media for fostering a moral panic, if not an actual rise in the frequency of such attacks. Scholarly research suggests that the media can potentially impact the prevalence of mass shootings in two respects: (i) some individuals may be inspired to mimic the actions of highly publicized offenders; and (ii) a more general contagion process may manifest as a temporary increase in the likelihood of shootings associated with a triggering event. In this study of mass shootings since 2000, we focus on short-term contagion, rather than imitation that can traverse years. Specifically, after highlighting the sequencing of news coverage prior and subsequent to mass shootings, we apply multivariate point process models to disentangle the correlated incidence of mass public shootings and news coverage of such events. The findings suggest that mass public shootings have a strong effect on the level of news reporting, but that news reporting on the topic has little impact, at least in the relative short-term, on the subsequent prevalence of mass shootings. Finally, the results appear to rule out the presence of strong self-excitation of mass shootings, placing clear limits on generalized short-term contagion effects. Supplementary files for this article are available online.

Abstract Zebra finches (Taeniopygia guttata) learn to produce songs in a manner reminiscent of spoken language development in humans. One candidate gene implicated in influencing learning is the N-methyl-D-aspartate (NMDA) subtype 2B glutamate receptor (NR2B). Consistent with this idea, NR2B levels are high in the song learning nucleus LMAN (lateral magnocellular nucleus of the anterior nidopallium) during juvenile vocal learning, and decreases to low levels in adults after learning is complete and the song becomes more stereotyped. To test for the role of NR2B in generating song plasticity, we manipulated NR2B expression in LMAN of adult male zebra finches by increasing its protein levels to those found in juvenile birds, using a lentivirus containing the full-length coding sequence of the human NR2B subunit. We found that increased NR2B expression in adult LMAN induced increases in song sequence diversity and slower song tempo more similar to juvenile songs, but also increased syllable repetitions similar to stuttering. We did not observe these effects in control birds with overexpression of NR2B outside of LMAN or with the green fluorescent protein (GFP) in LMAN. Our results suggest that low NR2B subunit expression in adult LMAN is important in conserving features of stereotyped adult courtship song.

The ability to imitate complex sounds is rare, and among birds has been found only in parrots, songbirds, and hummingbirds. Parrots exhibit the most advanced vocal mimicry among non-human animals. A few studies have noted differences in connectivity, brain position and shape in the vocal learning systems of parrots relative to songbirds and hummingbirds. However, only one parrot species, the budgerigar, has been examined and no differences in the presence of song system structures were found with other avian vocal learners. Motivated by questions of whether there are important differences in the vocal systems of parrots relative to other vocal learners, we used specialized constitutive gene expression, singing-driven gene expression, and neural connectivity tracing experiments to further characterize the song system of budgerigars and/or other parrots. We found that the parrot brain uniquely contains a song system within a song system. The parrot "core" song system is similar to the song systems of songbirds and hummingbirds, whereas the "shell" song system is unique to parrots. The core with only rudimentary shell regions were found in the New Zealand kea, representing one of the only living species at a basal divergence with all other parrots, implying that parrots evolved vocal learning systems at least 29 million years ago. Relative size differences in the core and shell regions occur among species, which we suggest could be related to species differences in vocal and cognitive abilities.

Objectives. To examine the independent and joint effects of state legislation on minimum age for purchasing handguns and background checks on the suicide of young adults aged 18 to 20 years. Methods. We used negative binomial regressions with fixed effects for year and generalized estimating equations for state to estimate the effects of state legislation on annual counts of firearm, nonfirearm, and total young adult suicides in all 50 US states from 1991 to 2020. Results. Minimum age laws decreased the incidence rate of firearm suicide among young adults, an effect that was amplified in states with permit to purchase laws; there was no effect on the nonfirearm or total suicide rate. Permit to purchase laws significantly decreased the young adult firearm suicide incidence rate by 39% (incidence rate ratio [IRR] = 0.61; 95% confidence interval [CI] = 0.51, 0.74) and the overall suicide incidence rate by 14% (IRR = 0.86; 95% CI = 0.75, 0.99), with no effect on the nonfirearm suicide rate. Conclusions. Permit to purchase laws are a more promising avenue for reducing young adult suicides than are age-based restrictions. ( Am J Public Health . 2024;114(8):805-813. https://doi.org/10.2105/AJPH.2024.307689).