The News Minute | November 12, 2014 | 3:00 pm ISTWe know that the weather has a profound physiological and psychological impact on us. Now, researchers at the Stanford University have analysed tweets for indications of mood changes and their correlations with the weather.According to them, some moods are clearly correlated with certain types of weather and while average temperature does not correlate with mood, a change in temperature does."People tend to be happier as temperature becomes cooler but feel uncomfortable with drastic temperature decrease," said lead researcher Jiwei Li from the Stanford University in the US.Higher temperatures also make people angrier."Snow is correlated with negative moods," Li added.Most moods follow a weekly pattern with peaks at the weekend."People tend to be the least angry, the least depressed and the least sleepy on weekends," Li said.For the study, they scanned the database of tweets geotagged to one of 32 major urban areas in the US such as New York, Chicago, Los Angeles, San Franciso and so on.Li and colleagues also filtered out tweets about national or international events such as the Haiti earthquake, the death of Michael Jackson and so on.The team then categorised the remaining tweets according to four different mood dimensions: anger-hostility, fatigue-inertia, depression-dejection and sleepiness-freshness.Finally, they used a machine learning algorithm to find correlations with the weather in these areas using a database from the National Oceanic and Atmospheric Administration."We found that cool temperature is linked with sleepiness and people tend to be fresher and fresher as temperature increases," the authors said in a report that appeared in the MIT Technological Review.IANS