I have continued the experiment I reported earlier on playing Dual-n-back game while monitoring my progression Heart Rate Variability (HRV). I have manually set the game to Dual-3-back, meaning I have to remember a location and letter that is three iterations in the past. For a full explanation of how much cognitive load that adds to the situation you can read Gwern’s FAQ on Dual-n-back here. I can tell you from experience that 3 back is a lot harder than 2 back. The data shows the difference in scores:
You can see I was reliably getting percent scores in the 70’s and 80’s playing 2 back. When I increased the difficulty to 3 back my scores dropped to the 30’s. An you can see a progression where the most recent plays are moving toward 50%. How has this effected my HRV? Here is my rMSSD for the last 8 sessions of 2 back and first 19 sessions of 3 back.
As I have reported before an rMSSD above 48 for a 30 second reading occurs when I am relaxed and feeling stress free. Each of these games are 4.5 minutes long, so that is 9 consecutive 30 second readings. You can see the 2 back games toward the end were averaging above 50 so I was feeling stress free during those sessions which makes sense because I my average score for those sessions was 77%. I had the feeling of having mastered that level.
When I started with 3 back the rMSSD dropped to an average of 43.3 for the first ten sessions. 3 back was definitely harder and I was seeing very slow progression in the scores. I recall feeling a bit negative about the process and unsure if I could get better at the task. I did not really try any strategies, I just tried to improve through repetition.
The last four 3 back sessions are interesting. At session fifteen I was thinking about how to move the score I decided to try focussing on only the location and “wing it” for remembering the audio cue. To my surprise BOTH measures went up. I saw better results and got interested about pushing this strategy. For the following sessions you can see both my scores and my rMSSD going up. My rMSSD average for those sessions is 54.25. I was enjoying the process because I saw there was a path to improvement.
What is intriguing is that my rMSSD (and stress) changed not as a result of the scores, but at the specific point I felt I had discovered a way to improve the process. My perception alone drove the change in HRV. My story about improvement and efficacy moved my stress level, not the performance of the game at all. So growth and learning is gradual, but our story about how the progression of the learning can be more dramatic.