What the study found on a London trading floor
In 2016, researchers tested 18 traders on a London trading floor for something unusual. They asked them to count their own heartbeat, without touching their pulse or using a device. Then they tracked those traders' performance over time, which allowed them to see whether this skill made any difference to their results.
The traders who were better at sensing their own heartbeat made more money, and they stayed in the market longer. They also scored better on the heartbeat test than a control group of non-traders, which suggests that interoceptive ability (the capacity to perceive internal bodily signals) might be part of what keeps you in this work.
The study was published in Scientific Reports by Kandasamy and colleagues, and it's one of the few pieces of research that directly links a measurable physiological skill to trading outcomes. What makes it stand out, in other words, is that it connects something you can test in the body to something that shows up in performance.
Why interoceptive ability matters (and what it doesn't prove)
Here's what the study shows, and what it doesn't. It found a correlation between heartbeat perception and performance, but that's not the same as proving causation. The researchers didn't test whether teaching someone to feel their heartbeat would make them more profitable, and they didn't measure profitability with a device instead of self-perception.
What it does suggest is that the signal from your body is relevant to your decisions, which aligns with what other research has found. Fenton-O'Creevy and colleagues showed in 2012 that more experienced traders had higher heart rate variability during volatile markets, and Lo and Repin found in 2002 that physiological responses during trading were measurable even in seasoned professionals.
The pattern across these studies is consistent, in the sense that similar findings appear across different contexts. Your body responds to what's happening in the market, and that response appears to be connected to how you perform.
The problem: most people can't do this
The traders in the Kandasamy study were better at sensing their heartbeat than the control group, but that doesn't mean they were perfect at it. Interoceptive ability varies widely, and most people aren't good at counting their own pulse without external feedback.
That's the gap between the research and real-world application, where theory meets the limits of everyday practice. If your ability to perceive your heartbeat predicts how well you trade, but you can't reliably perceive it, then the skill isn't accessible to you in the moment.
You can't improve what you can't measure, and you can't measure something you can't detect. This creates a circular problem, where the very thing that might help you stays out of reach because it remains invisible.
What SLD does differently
SLD doesn't teach you to feel your heartbeat, because that's not something most traders can do consistently. It measures your heart rate during your session, then shows you what was happening in your body when you clicked the button.
Where most journals ask you to rate your emotional state after the fact, SLD pulls the data from your wearable. Your heart rate was climbing three minutes before the bad trade, and you didn't notice it. That's not a judgment on your discipline, it's just what the data shows.
The Kandasamy study suggests that the internal signal matters for performance, which is why tracking it might make a difference. SLD makes that signal visible, so you don't have to guess whether you were calm or not.
Test the premise yourself
If interoceptive ability correlates with survival in trading, then the reverse question becomes testable. Does tracking your physiological state help you see patterns you couldn't see before, and can that awareness translate into better decisions over time?
SLD is in pilot phase right now, with 10 spots available for traders who want to test that premise. You log your trades, link your wearable, and see whether your heart rate tells you something your memory doesn't.
No promises about profitability, because that would be dishonest. Just the data, so you can decide what it means.
Test the tool that tracks what your body knew before your brain did, at stoplossdivision.com. It's designed to make the invisible visible, so you can see whether your state was influencing your choices all along.