How do you know if your chicken is cooked properly? It's complicated, say researchers

(CNN)What's your rule of thumb when you cook chicken? Is it done when the juices run clear? When it's no longer pink? Or do you test the texture of the meat?

None of these methods is foolproof, and even a meat thermometer may have drawbacks, according to a new study that investigated how people in five European countries cooked chicken.
"Most people think you can look at the color change from pink to white and that suggests it's ready," said Solveig Langsrud, a senior scientist at the Norwegian Institute of Food, Fisheries and Aquaculture Research.
    "We couldn't find anything in the scientific literature backing this up, so we decided to look into it."
      The researchers surveyed 3,969 people and interviewed and recorded video of 75 people from different age groups as they cooked chicken in their homes in the UK, France, Romania, Portugal and Norway. They focused on three groups: young single men, families with infants and elderly people over 70.
      They found the most common way of deciding whether the chicken was ready came down to the home cook's gut feel -- that is, timing it out based on prior experience of cooking a chicken fillet or other cut. Other methods that closely followed in popular use included looking at the surface of the meat, testing the texture with a fork or other implement and checking inside to see whether it were still pink.
      These chicken fillets were cooked to different temperatures.
      The researchers said, however, that their lab tests showed that changes in the color and texture of the chicken weren't reliable indicators of whether it was done -- at least not on their own.
        "The findings of the initial study corroborate multiple investigations that have reported that the majority of consumers continue to rely on sensorial qualities (color, juices, texture) to indicate that the chicken is fully cooked, and only a small number of them use a thermometer," said Francisco Diez-Gonzalez, professor and director of the Center for Food Safety at the University of Georgia in Griffin, Georgia.
        The study published Wednesday in the journal PLOS ONE.

        The heat is on. But how high do you go?

        Undercooked chicken can harbor harmful pathogens like salmonella and campylobacter. High temperatures can kill these microbes, but enough may survive to cause illness if meat is undercooked.
        Food should be cooked to 158 F (70 C) according to the World Health Organization, while the USDA advises that poultry should be cooked to an internal temperature of 165 F (73.8 C).