American Scientist

In this roundup, associate editor Nicholas Gerbis summarizes notable recent developments in scientific research, selected from reports compiled in the free electronic newsletter Sigma Xi SmartBrief.

The Brain’s Reality Check

Human imagination produces fanciful images by hijacking the neurological equipment the brain uses to process actual visual input. So how does our brain separate the visual from the visionary? Scientists at University College London suggest that certain frontal brain areas base this judgement on the strength of a “reality signal” from the bilateral fusiform gyrus in the midlevel visual cortex. Dreamed-up images produce weaker signals than visually seen objects do, possibly because the latter include signals from the eyes, whereas the former use only processes from within the brain. The team identified this mechanism through an experiment in which participants viewed a screen filled with visual noise and were told to perceive, imagine, or perceive and imagine a faint pattern of left- or right-slanted diagonal lines. Researchers noted changes in brain activity when the relevant pattern was absent, present, or present and oppositely oriented. When subjects were primed to imagine an image that was present, they became more confused regarding whether the pattern was really there. The findings have important implications for understanding perception, imagination, and our experience of reality.

Dijkstra, N., T. von Rein, P. Kok, and S. M. Fleming. 2025. A neural basis for distinguishing imagination from reality. Neuron 113:1–7.

Waste Forms Rocks in Decades

University of Glasgow scientists report that rocks can form from anthropogenic waste in less than 35 years. That’s a geological eyeblink compared to the thousands to millions of years nature takes to produce clastic rocks—sedimentary rocks composed of fragments (clasts) of eroded and transported stone—and demonstrates the rapid environmental impacts underway in our Anthropocene era. The rocks formed at Derwent Howe, a coastal industrial area in the United Kingdom where foundries dumped iron and steel furnace slag along the coastline from 1856 until the 1980s. Prior research shows numerous ways that human activities might speed up the rock cycle: Debris comes prebroken into clasts, precluding the need for weathering, and industrial materials often contain chemically reactive substances that help “glue” rocks together. But the study is the first to show a complete anthropoclastic rock cycle in which natural processes create stones from anthropogenic materials, transforming a loose sediment coast into a waste-rock platform containing detritus such as a 1934 King George V coin, car tires, fiberglass, and keys. The speed and scale at which the anthropoclastic rock cycle operates suggest an urgent need for new models and waste management practices.

Owen, A., J. M. MacDonald, and D. J. Brown. 2025. Evidence for a rapid anthropoclastic rock cycle. Geology 53:581.

Telecom Cables as Ocean Sensors

Maintaining sensors on the oceanic floor is difficult and expensive, but monitoring remains vital for conducting research, mitigating risks, and measuring climate change and tectonic activity. Now a team led by researchers at California Institute of Technology has converted a transatlantic telecom cable into a cost-effective sensor array for monitoring ocean pressure, tide fluctuations, and temperature changes. This transoceanic distributed sensing (TODS) works by unobtrusively detecting tiny timing variations in light signals as the distance they traverse changes due to cable lengthening or compression. Such changes can arise from strain (deformation from external forces), temperature changes, or vibrations. Such forces can be exerted by variations in tidal pressure, with which TODS strains correlated well, or by seismic activity or thermal expansion of the sea bed. Attempts to measure temperature met with mixed results and worked best at shallower depths (the cable’s depth ranges from 3 to 5 kilometers). The team is the first to detect sub-millihertz signals across the full length of a 5,900-kilometer cable, establishing 81 subsea sensors running from Portugal to Brazil, thereby enabling trans-Atlantic monitoring of slow, large-scale processes that less sensitive sensors might miss.

Liu, M., et al. 2025. Trans-oceanic distributed sensing of tides over telecommunication cable between Portugal and Brazil. Geophysical Research Letters 52:e2024GL114414.

First Signs Pterosaurs Ate Plants

For the first time, scientists have found direct signs of plant-eating among pterosaurs. The finding adds new evidence to wide-ranging arguments about the lifestyles of the first vertebrates to evolve the capacity for powered flight. The argument for herbivory rests chiefly on the preserved stomach contents, or consumulites, of Sinopterus atavismus remains from northeastern China. These mark the first consumulites uncovered from a pterodactyloid pterosaur; historically, experts had to infer pterosaur diets through indirect means such as comparing pterosaur morphologies to the anatomies of living animals with known eating patterns, resulting in hypothesized diets ranging from insects to animals to mollusks. When the team, led by researchers from the Chinese Academy of Sciences in Beijing, compared the makeup and shape of the pterosaur’s stomach contents with an international standard catalog of phytoliths (rocky plant remains), they found shapes suggesting a varied diet of broadleaf plants, woody plants, flowering plants, and ferns. However, because they could classify only 10 percent of the phytoliths, the authors recommend caution and further research. Even so, the remains suggest a birdlike two-chambered stomach, and the specimen’s bite strength, derived partly from the anatomy of its close cousin, Tapejara, also suggests an animal that ate hard plant matter such as seeds.

Shunxing, J., X. Zhang, Y. Wu, M. Zheng, A. W. A. Kellner, and X. Wang. 2025. First occurrence of phytoliths in pterosaurs—evidence for herbivory. Science Bulletin. doi.org/10.1016/j.scib.2025.06.040