>Are "tells" pseudoscience?"tells" are a real thing but I don't there's a 1 size fits all. I don't know what domain the science of reading tells would fall under, but I'd hazard a guess of it falling under the category of neurology.
see
https://en.wikipedia.org/wiki/Mirror_neuronIn order understand and properly interpret "tells" one must utilize mirror neurons. Some people's mirror neurons are more active than others so they're able to interpret other's tells better, but it's an intuitive process. I think it happens on a semi-concious or unconscious level, and I think there's not much science on that yet.
There are tells that are much more obvious. Such as looking upwards is a sign that someone is thinking. Looking to the left or right to avoid eye contact is a sign of deceit of dishonesty.
see
https://en.wikipedia.org/wiki/Cold_reading 
