The quantification in real time of the expansion state of tens of thousands of pigmented skin cells from cuttlefish is reported in this week’s Nature. These findings increase our understanding of the complex physiological transformations associated with the cuttlefish’s varying perceptual states - akin to thoughts worn on the skin.

Cuttlefish and octopuses have an unmatched ability to change the colour and textural appearance of their skin for camouflage or social communication, thanks to the controlled squeezing of myriads of pigmented skin cells called chromatophores. Tracking the expansion states of these chromatophores provides a quantitative description - and potentially even a neural description, by proxy - of the animals’ perceptual state in real time.

Gilles Laurent and colleagues developed computational and analytical methods to access this information from freely behaving cuttlefish. The authors filmed six animals in a tank over a period of weeks, and colour-classified the chromatophores of the cuttlefish’s dorsal mantle at single-cell resolution at 60 frames per second. They also tracked pattern dynamics by moving a hand above the cuttlefish, causing it to transition from dark to light. The authors examined this transition over several repeats and report that upon each stimulus the animal generated the same target patterns.

The authors suggest that these results enable an objective description of complex perceptual behaviour and that this approach could provide insights into the organizational principles underlying neural systems.