The first Rihanna song I ever heard was Unfaithful. I spent every car ride during the next few months staring dramatically out of the window, picturing a young woman with pale skin and long, dark, curly hair singing about an unfaithful lover.
If the first video by the YouTube creator PewDiePie I ever watched had not made it very clear that he is originally from Sweden (and therefore his native language is Swedish), I may have accredited his 'unique' use of English on a lack of intelligence or education.
For a long time, I thought Amy Winehouse was a curvy black woman, simply based on her voice.
As illustrated by the examples above, we judge others based upon how they use language and your voice. This is understandable – I challenge you to listen to a sound clip without forming some kind of mental image of the person speaking or singing – because language does form a large part of your identity. You use language to express your identity, be it in the language itself that you speak, the dialect you use in different situations if you are multi-dialectal, the vocabulary you use in different situations and even the tone and pitch of your voice. You also use language to physically tell people about who you are.
However, just as you cannot determine someone's entire identity by looking at one aspect like appearance or sex, studies have shown that you cannot use language to judge aspects of their identity that have absolutely nothing to do with language, such as trustworthiness and work ethic. The opening examples show that one cannot determine someone's appearance with absolute certainty solely based upon their voice.
Intelligence is another important aspect of identity that cannot be inferred from the way somebody speaks. A speaker of standard South African English is usually seen as more intelligent than a speaker of black South African English or someone speaking English with a very heavy Afrikaans accent. Because of the history of education in South Africa, a speaker of black South African English will generally not be regarded as well-educated. Because of this, a speaker of standard South African English will enjoy linguistic privilege.
So, if there are no scientifically proven connections between language and characteristics like trustworthiness, work ethic, intelligence and level of education, why do we make them? Making judgements based on someone's speech is just as wrong as making judgements based on their ethnicity or sex, but this issue has not enjoyed nearly as much attention as sexism or racism. Linguistic prejudice is a thing, but it needs to be a bigger thing in people's minds and conversations.