Google has been accused of racism after allegedly linking names usually associated with black people to adverts related to criminality.
A Harvard University professor found 'significant discrimination' after comparing the adverts which appear when searching a typically black name compared with those for typically white names.
Findings showed that names typically associated with black people were 25 per cent more likely to bring up adverts related to criminality.
The study by Latanya Sweeney contrasted online searches using names such as 'Ebony' and 'DeShawn,' with those such as 'Jill' and 'Geoffrey.'
She found that adverts posted alongside search results for names likely to belong to black people were more likely to offer services like background checks for arrests and criminal records.
Searches using white-sounding names were less likely to result in advert results which suggested criminality, Professor Sweeney's research indicated.
The findings are significant since Google searching the names of potential employees, clients or even friends and dates has become commonplace.
'Advantages of knowing such information when hiring or engaging with a person relate to trustworthiness,' Professor Sweeney writes in a paper published online in the journal arXiv.
Professor Sweeney gathered evidence by collecting more than 2,000 names which were suggestive of race.
She then entered these names plus surnames into Google and news agency Reuters' Google-powered search engine and looked at which adverts the search results returned.
While most names brought back adverts for public records, typically black names were much more likely to bring back those that included the word 'arrest'.
All the results came from background-checking service instantcheckmate.com.
In one particular case highlighted by Professor Sweeney, a search for the black-sounding names Latanya Farrell, Latanya Sweeney and Latanya Lockett all brought up adverts for arrest checking services.
However, subsequent investigation showed only one of the names, Latanya Lockett, had an arrest record linked to it.
'In comparison, searches for "Kristen Haring", "Kristen Sparrow" and "Kristen Lindquist" did not yield any instantcheckmate.com ads, only competitor ads, even though the company's database reports having records for all three names and arrest records for "Kristen Sparrow" and "Kristen Lindquist",' Professor Sweeney wrote.
She added: 'Together, these hand-picked examples describe the suspected pattern - ads suggesting arrest tend to appear with names associated with blacks and neutral ads or no ads tend to appear with names associated with whites, regardless of whether the company has an arrest record associated with the name.'
In the UK, black people are 3.3 times more likely than white people to be arrested for a crime and those from the mixed ethnic group 2.3 times more likely.
The findings raise 'questions as to whether Google's advertising technology exposes racial bias in society and how ad and search technology can develop to assure racial fairness,' Professor Sweeney said in a blog post.
Advertisers bid on terms, or key words, with high bidders getting their ads posted alongside corresponding search results.
Google defends the process as race-neutral, saying outcomes are driven by decisions by advertisers.
A spokesman said: 'AdWords does not conduct any racial profiling.
'We also have an "anti" and violence policy which states that we will not allow ads that advocate against an organisation, person or group of people.
'It is up to individual advertisers to decide which keywords they want to choose to trigger their ads.'
The study dated last week was funded in part by the National Science Foundation and a grant from Google.