P6 – PostureParrot

Group 7, Team Colonial

David, John, Horia

Project Summary

The Pos­turePar­rot helps users maintain good back posture while sitting.


The system that is being evaluated is the functional prototype of the PostureParrot and its accompanying GUI.  The purpose of this experiment is to determine whether our target audience will find the operation of the PostureParrot to be simple, intuitive and instructive.  It needs to be easy for users to wear the product and learn from its audible feedback and from the GUI’s visual feedback.

Implementation and Improvements

Link to P5: https://blogs.princeton.edu/humancomputerinterface/2013/04/22/p5-postureparrot/

Between P5 and P6, we have altered the list of tasks, now reintroducing a GUI that allows the user to set their default back posture, as well as alter the allowed wiggle room (degree that user can move without being notified) and time allowance (total time that user can deviate from default posture before being notified.) This GUI originally allowed the user to set the default back posture, as well as see changes in separate areas of the back over time; through our tests, we discovered that it was simpler, more refined, and more accessible to produce a compact device with a single component rather than a device that monitored multiple parts of the back. Overtime, we discovered that our fabric “reset” button embedded in the device was extremely unreliable, and, as a result, moved this functionality to our GUI.



To select our participants, we looked for Princeton students who studied while sitting.  To find these students, we went to an eating club library and asked sitting students if they would like to take part in our usability study.  Additionally, we asked them each a few questions to make sure that they were a part of our target user group.  For example, we asked them if they studied at desks a lot of the time or if they ever experienced back pain.


We performed the test at a table that was set up in an eating club.  We put a standard desk chair up against the table.  The only other equipment we used was our PostureParrot connected to a laptop.


(Easy) Set the default back posture of the PostureParrot.  This requires that you have already attached the device and opened the GUI.  The user should position himself so that he has good back posture   Then he should press the button on the GUI that says “Set Default Posture”.

(Medium) Deviate your back from the desired back posture and respond to the PostureParrot’s audible feedback.  After the user has set a default back posture,  the device will make a noise when the user deviates too far from it.  The user must correct their back posture back to the default to make the noise stop.

(Hard) Use the GUI to adjust the PostureParrot’s wiggle room and time allowance.  While the device is attached and the GUI is running, the user adjusts the values associated with wiggle room and time allowance and observes the effects.  The user should select a wiggle room and time allowance that they feel comfortable with.


For each participant, we first requested that they fill out the consent form, as well as their demographic data. We then gave them a quick demo, opening up the GUI and demonstrating how one attaches the device onto their shoulder. After beginning our video recording, we then asked the participant to sit before the laptop and attach the device themselves before proceeding to the three tasks. For each of these tasks, we explained to each participant what they were trying to achieve, and asked them to say aloud any concerns or observations as they arise (which we recorded by taking notes, in addition to any critical incidents that we see.) Once a task was complete, we paused to explain the goal of the next task. Once all three tasks were complete, we asked each participant to take a brief survey.

Test Measures

Our main goal for testing was to evaluate the level of difficulty associated with the different tasks.  In addition to making standard observations, we had the user fill out a questionnaire where they self-reported values pertaining to their satisfaction and level of difficulty with different aspects of the device.  The following were our questions:

  • Please rate the difficulty of task 1 (setting the default posture)
  • Please rate the difficulty of task 2 (deviating from default back posture)
  • Please rate the difficulty of finding a good “wiggle-room” value
  • Please rate the difficulty of finding a good “time-allowance” value
  • Please rate how intuitive the device was over-all
  • Please provide any additional comments / potential improvements

Results and Discussion

Through our observational notes, we noticed that users were confused when asked to set the default back posture. This could potentially because there was no confirmation when a user selected the button to set their desired back posture. To alleviate this, we plan on making the arduino beep in confirmation when a new default is set. We also discovered a bug that was present in our GUI; due to some odd communication between Processing and Arduino, values for both wiggle room and time allowance become distorted when the increment/decrement buttons were quickly selected. Fixing this problem will involve looking at the values that are being passed between the two programs, as well as how various delays (intentional delays, tone delays, etc) are affecting results.

Through our observational notes, we learned that wiggle room and time allowance were not intrinsically intuitive and require additional explanation. In future iterations, this may simply require a small text snippet in the GUI that briefly explains what each value represents. We also found that our default value for wiggle room was far too lenient; in our final iteration, we will have refined values so that the device responds appropriately to those using it, especially first-time users. We also discovered that sometimes it becomes difficult finding your original posture, especially when the wiggle room is relatively unforgiving. One potential way of addressing this in our next version is to have the tone respond according to your deviance from the base posture; for example, we could have it so it increases in frequency the farther you deviate. However, perhaps this functionality may be unnecessary, since users can always reset their desired back posture.

From our questionnaire, we discovered that the first two tasks were relatively easy; this shows that although our interface was slightly surprising without a notification, it was still an easy task to accomplish. The last task – regarding the two variables – was generally more difficult; although this was most likely due to the distorted values, it would be useful to find out if there were additional reasons for why this task was unintuitive. For the additional comments part of the questionnaire, we received a comment about how the adhesive on the device made it difficult to keep it on the user’s shoulder.  Another comment that we received stated that it was possible to achieve the same “good posture” angle when slouching.  Although this is a valid point, the user did have to work to find this same angle and our adjustable wiggle room and time allowance should compensate for this.  To completely eliminate this issue we would need to keep track of lower back posture too, something that would require the device to be more cumbersome (what we moved away from after P5).

There were some limitations that we found while conducting our usability study.  Due to our small population size, it was difficult to get an accurate idea for what users thought were optimal wiggle room and time allowance values.  It would be interesting to track the final wiggle room and time allowance values settled upon by many different users.  Another limitation that we had in our sample population was that our test users all had very low back pain.  Each of our users were male as well, meaning that we were not able to distinguish differences in usage by gender.  After tracking each user’s major, we also thought that it would be interesting to see how people with different lifestyles (lifestyles associated with computer science majors, english, etc) would affect the product usage.  This would also require a larger population.


Consent and Demographic Form



Name: ________________________

Please rate the difficulty of task 1 (setting the default posture)
1 – difficult 2 3 4 5 6 7 – easy

Please rate the difficulty of task 2 (deviating from default back posture)
1 – difficult 2 3 4 5 6 7 – easy

Please rate the difficulty of finding a good “wiggle-room” value
1 – difficult 2 3 4 5 6 7 – easy

Please rate the difficulty of finding a good “time-allowance” value
1 – difficult 2 3 4 5 6 7 – easy

Please rate how intuitive the device was, over-all
1 – not intuitive 2 3 4 5 6 7 – very intuitive

Any additional comments / potential improvements:

Observational Notes & Questionnaire Responses

Max J.

Task #1

  • 7:06 Clicks default posture and laughs (potentially because nothing happened on either the interface or the device)

Task #2

  • 7:06 Laughs (potentially because he needs to bend his back to a great degree)

Task #3

  • 7:08 Moves GUI around screen
  • 7:08 Finds a bug: if user clicks buttons too quickly, values are corrupted
  • 7:08 Device falls off shoulder and needed to be placed on the shoulder again
  • 7:09 Experiments with wiggle room until a desirable value is found

Questionnaire Responses

  1. 7
  2. 7
  3. 3 (“buggy”)
  4. 3
  5. 7
  6. Additional Comments: Better tape [emphasis his]

Zhexiang W.

Task #1

  • 7:25 Confused by no confirmation after selecting default

Task #2

  • 7:26 Comments that the default wiggle room is extremely large
  • 7:27 Wonders if there is a time delay / if he should move slower while testing

Task #3

  • 7:27 Minimizes the range of wiggle room, is pleased with stricter values

Questionnaire Responses

  1. 6
  2. 6
  3. 2
  4. 5
  5. 6
  6. Additional Comments: None

Andy H.

Task #1

  • 7:45 Success!

Task #2

  • 7:45 Tries different ranges of motions: forward-back, left-right, diagonally

Task #3

  • 7:47 Has difficult time finding original position
  • 7:48 Tries device moving forward and backward, but not any other direction

Questionnaire Responses

  1. 6
  2. 5-6 (circled together)
  3. 5-6
  4. 5-6
  5. 4
  6. Additional Comments: Needs to keep track of lower back posture too – same “angle” can be achieved w/ both slouching and “good” posture