Braun here from Human Precision. A reaction result includes seeing, deciding and responding. Processing speed is a broader cognitive idea. Here is the practical explanation and the limit that matters when using a browser test.
Reaction time is a chain
A reaction task measures elapsed time from a signal to an observable response. That chain can include visual detection, attention, response selection, movement preparation and the physical input. A simple reaction task minimizes decisions; more complex tasks add them.
Processing speed is broader
Processing speed generally refers to how efficiently a person performs relatively simple cognitive operations. Professional assessment may sample visual scanning, symbol matching, written output or other tasks under standardized conditions. One browser click cannot represent that whole construct.
Movement and devices matter
A person may process the signal quickly while responding through slower hardware or a slower movement. Conversely, a practised motor response can improve while broader reasoning remains unchanged. That is why Human Precision reports reaction as one skill within a six-skill daily profile.
Use the right question
Use a reaction test when the question is how quickly you respond to a specific signal under these conditions. Use a broader reasoning or professional assessment when the question concerns several cognitive abilities. The Human Precision IQ-style test provides a separate Reasoning Index, but it is still recreational and not clinical.
The practical takeaway
Track reaction time as a specific performance measure. Do not turn it into a claim about intelligence, health or real-world safety. For a broader daily picture, combine it with timing, accuracy, memory, focus and rhythm in the official daily test.
Human Precision provides recreational browser measurements. Device latency, practice, attention and environment affect results. Do not use a score for medical, education, employment, driving or safety decisions.