Monthly Archives: October 2014

Dual N-Back, Learning and Heart Rate Variability

Following my Heart Rate Variability, Learning and Flow study I took the recommendations from fellow quantified selfers and ran another round of sessions using a Dual N-Back game produced by the Brain Workshop.

What I did:

  • played a Dual 2-Back brain game on my Mac once or twice sitting at the same location in the morning each day for 8 days,
  • set the game for 90 trials that lasted anywhere from 273 to 282 seconds per session resulting in a measured success score that was expressed in terms of % correct,
  • measured the total heart rate coherence accumulated points score as given by Heartmath Pro over the total session,
  • divided the total accumulated points per session by the number of minutes to derive a “points per minute” score per session,
  • after entering that data into excel graphed the resulting points per session over the learning cycle.

How I did it:

Everything for this study was executed on the Mac. Heartmath Pro, the DualNBack game and excel were all windows on the Mac screen. Because I had set a disciplined approach to the first brain game I simply rotated the method in here.

As before I started the Heartmath Pro and waited until 30 seconds had elapsed so I was getting an HRV based cardiac coherence reading. After the coherence reading began I would start the Dual 2-Back game. The game was approximately 4.5 minutes to play. Here is a short YouTube video showing the mechanic of a Dual N-Back game.

Playing Dual 2-Back meant I was remembering the letter and location shown two iterations prior to the one being show on the screen currently.

What I Learned:

My correct answer percentage per session increased linearly the more I played. When I started I played using instinct then begin using a simple strategy to track the different elements around session 9. From there the learning continued but it was still linear. The strategy alone did not take the scores immediately higher, but it did enable continued improvement.

Slide1My Heart Rate Variability (HRV) also steadily increased the more I played. The points/minute proxy for HRV started at a low of 10 when I started playing and was in the 25 to 30 range at the 15 through 17th session. My subjective experience was of stress and concentration in the early session then more relaxed in the later sessions, mostly because I had worked out a strategy and attributed different scores to my having implemented the strategy well or not. Specifically, my mindset went from “I don’t know how to improve” in sessions 1 through 8 to “I need to implement a known strategy better” in 9 through 17. Here are the points/minute results over the sessions:


Dual N-back demands constant attention, unlike the nearly autonomous reactions the category brain game allowed after repeated play. My experience with Dual N-back was consistent low level stress where the category game was more like “zoning out” and watching my fingers hit the screen. In comparison to the range of 10 to 30 points/minute in the Dual N-back game the category game points/minute were routinely between 30 and 50 as shown here:


One insight I gleaned was that there is no “know it” or “don’t know it” binary state with respect to mastering a task. Knowledge and capability steadily increase as reflected in the quality of the output. Physiological stress decreases steadily as reflected in the increase in HRV. So my own tendency to think of mastery as binary is incorrect. Mastery at the capability and physiological level is a continuum and we move linearly along it. And movement along that continuum is as much about belief in the ability to improve as it is about underlying capability.

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HRV, Simple Games & Imagination

After feedback from Bob and Gwern on the learning post I have started collecting heart rate variability (HRV) while playing Dual-N-Back game that Gwern recommended. Dual-N-Back is much more intense than the simple category recognition game I have been measuring. I will share the results there when I gave a good amount of data. Out of curiousity I kept playing the simple game from the first post and continued recording the results.

What I have seen with continued plays of that first simple game has surprised me. According to the principles in Csikszentmihalyi’s Flow I would expect a stress response from my HRV reading in the beginning, a relaxed (high) HRV when I was in Flow then for the reading to taper off as I become bored with the task. I’m not finding that. Here is the graph:


What has happened is after the first sessions of learning how to use the category game (session 1 through 6) my HRV became relaxed and has stayed there. In fact the “up-down-up-down” you see on the graph is an expression of the fact I do two or three sessions a day and sometimes I get into a groove in different sessions. The graph if you average the sessions across the day eliminates this and is clearer on how stable my HRV has been once I familiarized myself with the game:


So this particular category game engages my attention enough to get me into a relaxed state that yields consistently higher HRV. I am a bit thoughtful during the task and at times my mind wanders because I am bored. And the numbers show that I am averaging a much higher HRV overall after having become familiar with the task.

What I see in the different session scores is a state of attention playing out. When I am engaged and focus my HRV as reflected in the points scores is higher. Each time I play I use the same tablet at the same desk in the same sound and light environment. The task is the same, and I usually score the same amount of points. What is different is whether I have a story in my head that I should be doing something else or have been doing the task for too long. That story is completely from my imagination. So imagination drives HRV as much as anything.

Heart Rate Variability, Learning & Flow

I looked at how my Heart Rate Variability (HRV) changed through the process of learning a simple task from introduction of the activity through to a point where the task was nearly pre-conscious and automatic. I compared the change in HRV to Csikszentmihalyi’s concept of moving from anxiety through Flow to boredom.

What I did:

  • played an Android based “brain game” twice through for approximately 4.5 minutes per session for twelve sessions,
  • measured the total heart rate coherence accumulated points score as given by Heartmath Pro over the total session,
  • divided the total accumulated points per session by the number of minutes to derive a “points per minute” score per session,
  • after entering that data into excel graphed the resulting points per session over the learning cycle.

How I did it:

In each session I would start Heartmath Pro and wait until 30 seconds had elapsed so I was getting an HRV based cardiac coherence reading. As soon as software started getting this reading started I would begin to play “Mind Games” on a Nexus 7 tablet. The game I played was 120 seconds long and included choosing one of four categories appropriate for a shown picture. The choices were cards, dice, cars or people and this example screenshot shows an image for a car with the four buttons below:



I played two repetitions of the 120 second game per HRV reading session for an approximate total session length of 4.5 minutes and two sessions a day for six days.

Heartmath Pro awards points per five second interval based on a “coherence score.” The score is based on the ratio of Low Frequency cardiac output to High Frequency, where cardiac coherence is considered to be achieved when all frequencies group in the Low Frequency band around .1Hz. Every five seconds the software awards achievement points based on the coherence score, meaning if your coherence score was 3.5 for that five seconds the software adds 3.5 points to your points total. The final outcome of a session looks like the this:


This scoring is a proxy for how variable your heart rate was during a session and thus how relaxed your physiology was in the period. Comparing the points total per minute to other measures like LF/HF and rMSSD show that higher points per minute and more “stress free” LF/HF and rMSSD correlate.

Once the sessions were completed I entered the session length and score in an excel spreadsheet which then calculated the points/minute for that session. In the session shown above 138 achievement points divided by 4.52 minutes gave an outcome of 40.9 points/minute. Scores playing the game over the twelve sessions ranged from 21.0 to 52.3 points/minute.

What I learned:

My initial idea was to avoid creating stress with the mind game by not paying attention to the mind game score, which was a measure of correctly categorized images. I was trying to only engage my attention and take a reading of HRV. I wanted to compare my HRV during engaged attention to a baseline where I let my mind wander and to when I was working on a computer. It was in session seven where I entered a very relaxed state and both the points/session and the mind game scores were going noticeably upward that I started looking at this learning curve in isolation.

In that seventh session I entered a relaxed state and no longer had to think about the answer as the image flashed on the screen. My fingers just moved. By sessions eight through eleven I was watching my fingers move without really thinking at all. And time, while it did not disappear, was no longer in my attention. I thought I may have entered a state described by Csikszentmihalyi’s Flow theory where  challenge and skills balance, as shown in this graph:

Flow Channel Image

When undertaking a task and the challenges match the skills and feedback is immediate one enters a relaxed and enjoyable state where time seems to disappear and the action just emerges. In the seventh and eighth sessions I realized this might be happening. Here is how that change in state was reflected in my HRV readings:


As higher HRV is associated with a relaxed state, what we see here is my physiological reaction to a challenge of a uniform difficulty was becoming more relaxed with repetition.

My subjective experience in sessions one through five was that of feeling “alert in the head” meaning I was calculating the answers as the images came up. And I was keenly aware of the time during each session and recall saying “only 20 seconds to go” or “only one more session.” This was a state of low level stress and anxiety.

Session six still felt like that but the HRV points/minute score was starting upward. By session seven the subjective experience started to change. I was relaxed during those sessions and time, while not completely gone, seemed to fade. My HRV points/minute continued upward. During session eleven and twelve the scores seemed to drop. I was doing the brain game automatically and not feeling stress of doing the game but my mind was starting to wander to other topics. Boredom had begun.

Using the Flow chart this is what I think the HRV chart shows:


In the first five sessions my HRV reading was an average of 25 points/minute. As subjectively I began entering the Flow state from session six through ten my average HRV reading was 43 points/minute. During session 11 and 12 as my mind started to wander a bit the average on those sessions was 35 points per minute. Not stress, but not as relaxed and engaged.

Issues and Next Steps:

The issue here is I am writing this up before gathering sufficient data to see the full curve. For example, if I keep playing the game to absolute stultifying boredom where does the HRV points/minute level out? And how do I add challenge that is compatible with the “learned skill” of choosing the four categories?

The next steps are to see if HRV can be an indicator of location on the Flow continuum with respect to a learning task. If so, the challenge inherent in that task can be adjusted if the HRV readings indicatate that the learner is either 1) not emerging from early stages of learning anxiety or 2) the learner is dropping into a state of boredom because the task is mastered.

The Problem of Split Attention

In a heart rate session today I was in nice focus and high coherence until I thought of a to-do that I had to take care of later in the day. There was a navigational “I have to be somewhere else” feel and at that moment my RR interbeat interval went sideways as shown below in the red circle:



What was happening? In that moment I was trying to hold two things in my attention – one my breath as it followed the up and down journey of my interbeat interval, and the second the phone call I had to make. My nervous system then dropped the variability of my heart rate.

After recognizing the moment of split attention I returned my attention to my breath and the variability returned. In this case thought clearly triggered a change in variability, and releasing the thought returned the variability to its start point.

What was happening? A hypothesis is that I overwhelmed my conscious processing capacity of 126 bits per second as described by Csikszentmihalyi’s concept of Flow. Flow is a very fashionable framework and I think it is useful. Three things are necessary for Flow when undertaking a task – clear goals, clear feedback and a perceived balance of challenge versus perceived skills.

The task I was engaged in was focussing on my heart rate for 30 minutes. I perceived that I could make the phone call, so I was not out of balance in that sense. There was no feedback change. I think what happened is that I questioned my goals – should I instead be making the phone call versus sitting measuring heart rate variability?

Maintaining the integrity of moment to moment attention somehow has to be tied into how I prioritize my actions. From where does the framework for prioritizing actions come? It may be a shortcut to maintaining a lower level of stress.