These two meters are supposed to help you “develop a sense for recognizing critical game positions” by alerting you to sharp tactical situations or major positional changes. These gauges oscillate depending on the sharpness and mating possibilities of the position. The gauges measure the potential that something important is about to happen.
The Mate-O-Meter tells you how much danger the Kings are in and the Hotness meter rises when the position enters a sharp tactical phase or, in some cases, it measures changes in positional features like material exchanges, the win of material or strong or weak positional features like pawn positions or piece mobility. There’s also a small light that glows red when the engine is in the process of making evaluations and when the bulb goes out, the engine has completed the evaluation.
The exact measurements aren’t so important as the movement of the meters. If you see the needles rising there are tactical opportunities, positional motifs or mate threats on the horizon. Checks and captures move the needle up. If the needles are falling the position is becoming more stable.
I was curious to see how this might work in one of my own games so played through the game below which was played many years ago against a veteran USCF Expert. I resigned the game because I saw ghosts and somehow thought I was completely busted. Immediately after the game, a visiting master from Chicago who had been watching the game, pointed out things weren’t as bad as I thought and I could have played on. It’s been 51 years since I played this game and I’m still upset about having resigned too soon!
The Mate-O-Meter never moved until I played 17…Qc7 threatening a mate in one and after that it dropped back to about 1.0 and stayed there. As for the Hot meter, starting with my 11…d5?!, it bounced around between 3.5 to 8.2 for the rest of the game. I guess what it was telling me was that the position was complicated, but I already knew that. The meters are fun to watch, but personally, I didn’t find them to be much help.