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Like humans, some song sparrows are more effusive than others, at least when it comes to defending their territories. New UW findings show that consistent individual differences exist not only for how aggressive individual song sparrows are but also for how much they use their signals to communicate their aggressive intentions.

The basics of how a muscle generates power remain the same: Filaments of myosin tugging on filaments of actin shorten, or contract, the muscle – but the power doesn’t just come from what’s happening straight up and down the length of the muscle, as has been assumed for 50 years. The rest of the force should be credited to the lattice work of filaments as it expands outward in bulging muscle – whether in a body builder’s buff biceps or the calves of a sinewy marathon runner.