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What is Plasticity?

It’s an auditory discrimination game — that is, a game which tests and improves your ability to distinguish between similar sounds based on their frequency (pitch). You hear two sounds, which may have the same or different frequency (with 50-50 probability) and your job is to say whether they have the same frequency or different frequencies. At first, the differences are fairly obvious, but as you level up, they become smaller and smaller, which makes your job harder.

If you have pure-tone tinnitus, Plasticity may help alleviate it, but it’s a long shot.

What are the basic rules of the game?

You start out with several lives (depending on the difficulty level). Every time you get an answer wrong, you lose a life. Every time you advance to a higher level, you gain a life, but only the first time you reach that level.

One of the sounds in a pair is always a tone from the twelve-tone equal temperament system. In other words, one of the tones (either the first or the second one) always has the frequency of one of the piano keys. The other tone is either identical or slightly lower or higher.

On each subsequent level, the differences between sounds are smaller, but you get more points for each correct answer. For example, on level 1, the difference is 1 tone and you get 50 points per correct answer; on level 2, it’s ~0.71 of a tone and 100 points; on level 5, it’s ~0.26 of a tone and 1,000 points.

You can play the sounds again by clicking the speaker icon in the upper right corner. After you give your answer, you can also see the exact frequencies that you heard by pointing your mouse at the gauge just below the speaker icon.

How do you advance to the next level?

To advance to the next level, you have to convince Plasticity that you can actually tell the sounds apart and are not just guessing. The game uses probability theory to determine that. Specifically, it looks at your scores for up to 8 previous questions on the current level and calculates the probability that someone (I always imagine a monkey) would match or beat your result by choosing answers randomly. If this probability is low enough, the game assumes your results could not have been achieved by chance, and moves you up to the next level.

The rules for dropping to a lower level are similar. If a monkey would perform better than you more than 3/4 of the time, the game assumes you’re guessing and drops you to a lower level.

What are the differences between the difficulty levels?

On Normal, each beep is 0.25 seconds. On Harder, each beep is 0.2 seconds. On Hardest, each beep is 0.2 seconds and there are random volume differences between beeps.

What are the system requirements?

The current version of Plasticity uses the W3C Web Audio API, and has been tested to work in Firefox 28 and Chrome 33. Please note that, as of 2014, Web Audio is a “bleeding edge” feature and browser support is inconsistent and buggy.

Historical note: Plasticity initially used the Mozilla Audio Data API, introduced in Firefox 4. In Firefox 28, support for this API was dropped in favor of the standardized W3C Web Audio API. In March/April 2014, I rewrote the audio functions of Plasticity in the Web Audio API.

What’s your high score?

3,334,250 (Level 12) on Normal difficulty.

Why did you make Plasticity?

I have pure-tone tinnitus (a phantom ringing sound in my head). I wanted to help myself and others with this condition by checking whether it can be alleviated by “rewiring” the auditory cortex through simple training. (The name Plasticity refers to the ability of the brain to reorganize in response to input from the environment.)

So far I have tried Plasticity on myself and the results are inconclusive. More information about Plasticity and tinnitus is available on a separate page.