People judge how trustworthy you are within half a second

How long do you have to make a good first impression? About half a second, according to a new research.
Scientists have discovered that humans decide whether someone is trustworthy within the first 500 milliseconds of hearing their voice.
Psychologists from universities of Glasgow, Scotland, and Princeton, US, have shown that a simple 'Hello' is enough to allow most people to draw conclusions about personality type.
Also, people are able to make these judgements without seeing the person to whom we are speaking.
A study showed recordings of people saying hello and asked test subjects to rank them according to 10 pre-defined personality traits including trustworthiness, dominance, attractiveness and warmth.

The study found that most of the recorded voices elicited the same response from participants and that these opinions were formed rapidly on hearing the voices for only 300-500 milliseconds.

This suggests that the tone of voice you use when saying hello directly and immediately informs the first impression of the person to whom you are speaking.
The most important traits identified were trustworthiness and dominance. The study found that males who raised their tone and women who alternated the pitch of their voices are seen as more trustworthy.
Dominance is partly indicated by lowering the pitch, but more so by changes in 'formant dispersion', which are adjustments of your voice caused by the structure of your throat.

The fact that the human mind is capable of coming to these conclusions so quickly and irrespective of visual cues implies that this is an ability that may have evolved in our recent history when decisions on who to trust and approach were crucial to our species' survival.
"It is amazing that from such short bursts of speech you can get such a definite impression of a person. And more so that, irrespective of whether it is accurate, your impression is the same as what the other listeners get," said Dr Phil McAleer, from the Voice Neurocognition Laboratory, University of Glasgow, who led the study.

"It is perhaps also consistent that we are most attuned to recognising signs of trustworthiness and dominance, two traits that would have been central to our survival as we evolved," McAleer said.