A signal is not an explanation
Heart rate, heart-rate variability, skin conductance, breathing or an image pattern are measurements. The meaning assigned to them is interpretation. The same signal may accompany effort, excitement, anxiety, fatigue or an environmental change, so context is essential.
What is a closed feedback loop?
In biofeedback, the user receives real-time information about a selected signal and changes behaviour, such as breathing or posture. The system shows whether the signal changes. This creates a closed loop: measurement, response, new measurement. It is most useful when the protocol is repeatable.
Subjective ratings are still data
A wellbeing score is not an objective physiological measurement, but it is still useful information. A well-designed journal can record mood, sleep quality, stress and expectations. Comparing these notes with a physiological signal can be valuable as long as one is not presented as direct proof of the other.
Reducing self-deception
Predefined criteria, blinded conditions, control measurements and repetition reduce the chance of interpreting a result only in line with expectations. In personal use, automatic timestamps, immutable records and displaying all measurements—not only the most attractive ones—are also helpful.
What a responsible application should show
A responsible application should report signal quality, sensor limitations, calculation method and uncertainty. It should not convert a result into a medical diagnosis. It can help users observe patterns while preserving room for professional judgement and healthy scepticism.