Thank you for your interest in the tone-deafness test. In response to your questions we have put together a list of frequently-asked questions:
Tone-deafness, also known as congenital amusia, is typically an inability to sing in tune, although affected individuals also have an inability to discriminate pitches. How one ties into the other is a matter of ongoing research in several labs across the globe. One way of testing for tone-deafness is using the Montreal Battery for Evaluation of Amusia , in which you hear two melodies and decide whether they are same or different, and scoring below a cutoff of 70% classifies you as amusic. In our study , in addition to using the Montreal Battery we also used a psychophysical criterion of how well you can tell two tones apart. By administering a test similar to the one you took, we could obtain a frequency threshold difference (in Hertz, or Hz) that indicates the smallest difference between two pitches that you can reliably identify. The larger this number is, the more like you are tone-deaf. People whose pitch-discrimination thresholds were worse than one semitone (around 32 Hz in this test which tests your threshold at 500 Hz) were identified as tone-deaf. Those whose thresholds were between half a semitone (16 Hz) and one semitone were identified as slightly tone-deaf.
Reports of tone-deafness have ranged from 4 %  to a self-reported rate of 17 % . This variability among reports arises from differences in tests and definitions for tone-deafness. To assess the incidence of tone-deafness using the present criterion of being unable to distinguish tones at more than one semitone, we analyzed data from online respondents obtained through musicianbrain.com. Figures 1 and 2 below illustrate the results from 33,223 of the participants of our online survey so far.
Figure 1. Distribution of pitch discrimination thresholds among our 33,223 online respondents.
Figure 2. Estimated rates of tone-deaf, slightly tone-deaf and non-tone-deaf respondents based on our online listening test.
Based on data from 33,223 online respondents, we saw an estimated rate of 7 % tone-deaf and 9 % slightly tone-deaf participants. Although results may be influenced by selection bias (i.e. more people who suspected they were tone-deaf might choose to take the test), the rate of 7 % is within the limits of other published reports using smaller sample sizes.
It has been shown that tone-deafness does run in families. In 2007 it was estimated that 39% of first-degree relatives of tone-deaf people are also tone-deaf, as opposed to only 3% in control families . This effect is especially prominent among siblings and is significant even after controlling for musical training within families. However, researchers believe that more than one gene is responsible for tone-deafness and that the disorder is a result of gene-environment interactions. The precise genes that are responsible for tone-deafness are not yet known.
Language and music recruit many of the same brain regions, including areas responsible for sound perception, categorization, comprehension, memory, and production [6-8]. In 2008 our lab showed that verbal ability is enhanced among children with musical training and that children with dyslexia had problems in music discrimination tasks that correlated with their phonological skills ; furthermore, children who received at least three years of musical training performed better than musically untrained controls in vocabulary and nonverbal reasoning skills .
Pitch modulations in normal speech are typically much coarser than they are in music; thus, some people may be able to hear pitch changes in speech even if they are unable to hear pitch changes in music. Additionally, in our previous paper we had shown that tone-deaf people can often produce what they cannot consciously perceive . When given two pitches, tone-deaf people who cannot tell which one is higher can paradoxically reproduce these pitches in the correct direction, although with some over- and undershoot This suggests that there are multiple, direct and indirect, auditor-motor pathways that enable hearing and speaking, some of which may not be under conscious control. Thus, although tone-deaf people may no conscious ability to tell pitch differences, they may have an unconscious ability to produce them. This explains why tone-deaf people can still speak normally.
There is some evidence that tone language speakers (e.g. Mandarin Chinese, Bantu languages, some Southeastern Asian languages) are less likely to be affected by tone-deafness, suggesting that both genetics and environment may have contributed to tone-deafness. However, the ability to produce tones that one cannot consciously perceive  probably enables tone-deaf people to speak normally, both for tone languages and for pitch information (prosody) in other “non-tonal” languages such as English.
Pitch discrimination and production skills can definitely improve with practice and the appropriate training. Also, much evidence on neuroplasticity  suggests that brain changes can occur after rigorous training in listening to music, playing an instrument, and singing. Perhaps with enough practice, plastic changes and rewiring can occur so as to overcome the possible neural deficits that might underlie tone-deafness.
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