Adolescents math anxiety is commonly assessed using questionnaires that identified the anxiety experienced solving arith-metic problems. A more nuanced understanding of math anxiety would be gained by investigating anxiety associated withmath problems encountered in school at the time they are encountered. To this end, we investigated the anxiety associ-ated with algebraic problem solving ability relationships in 129 14-year-olds. We varied problem difficulty and the timeallowed to solve problems, and assessed students anxiety concurrently as they solved problems. Latent variable mixturemodelling revealed meaningfully different patterns of algebra ability and anxiety relationships that changed as a functionof problem difficulty and time pressure. A second study, examining 257 13- to 15-year-olds, successfully replicated theStudy 1 findings. The results highlight the value of using latent variable analysis to identify subgroup patterns of abilitiesand caution against making overly general claims about the role of anxiety in math problem solving.

Magnetic skyrmions are topologically protected spin textures that exhibit fascinating physical behaviours and large potential in highly energy-efficient spintronic device applications. The main obstacles so far are that skyrmions have been observed in only a few exotic materials and at low temperatures, and fast current-driven motion of individual skyrmions has not yet been achieved. Here, we report the observation of stable magnetic skyrmions at room temperature in ultrathin transition metal ferromagnets with magnetic transmission soft X-ray microscopy. We demonstrate the ability to generate stable skyrmion lattices and drive trains of individual skyrmions by short current pulses along a magnetic racetrack at speeds exceeding 100 m s(-1) as required for applications. Our findings provide experimental evidence of recent predictions and open the door to room-temperature skyrmion spintronics in robust thin-film heterostructures.