This is as detailed a description as the article gives in how they detect objects? This explanation does not seem very helpful since I assume the glass disks were not jumping up and down. Is there any more information available on how they sense?
I only glanced at it, but noticed that they hypothesized that the organism uses mechanosensation involving rhythmic pulling on the substrate and interpretation of changes in things like tension, compression or mechanical strain.
https://www.researchgate.net/publication/340090261_Mechanose...
Today is Sci-Hub anniversary the project is 10 years old!
I'm going to publish 2,337,229 new articles to celebrate the date. They will be available on the website in a few hours (how about the lawsuit in India you may ask: our lawyers say that restriction is expired already)
https://nitter.kavin.rocks/ringo_ring/status/143435621720862...
> Physarum is widely known to grow in a pulsatile manner, which consists of a forward growth phase and a reverse streaming phase during which the cytoplasm is retracted away from the growth regions (Figure 8A). We have observed that this oscillation is critical for Physarum mechanosensation and that interrupting it by changing the substrate stiffness (Figure 4) or interfering with the oscillations (Figure 6) prevents accurate decision making. Thus, we propose a theoretical model of Physarum navigation where this oscillatory behavior acts as a sample-and- integrate function (Figure 8B): the growth regions sample the environment during the growth phase, optimize the direction of the network tubes during the reverse streaming phase by inducing internal tension in the Physarum network which then aligns future growth of the growth regions.
So basically the slime mold pulls back on the substrate and feels for strain gradients.