Background: The 12th of March 2020 the Stockholm stock market fell close to eleven percent, the biggest decline on the market in modern time, as a result of the Covid-19 virus. Earlier studies have found that many individual investors make ill-considered decisions during sharp price falls which don't benefit their economic interest and that every new financial crisis offers new possibilities to expand the understanding about what underlying factors that are behind the crisis. Studies about psychological shortcomings have earlier been conducted, but not in connection with a stock market crash as a result of a pandemic, which means that there is not much research within the area. Therefore, there is an incentive to investigate which psychological biases individual investors were affected by during the corona crisis. Purpose: The purpose of this thesis is to study how a number of Swedish individual investors acted on the stock market during the corona crisis and if it varies depending on how much capital they manage. Which of the psychological biases herd behaviour, the disposition effect, loss aversion and extrapolation bias the individual investors that were interviewed was affected by and how they reasoned during the sharp stock market decline in March 2020. Method: The thesis has been conducted by a qualitative method to fulfil its purpose. The data collection consists of 10 semi-structured interviews with Swedish individual investors and statistics from the stockbroker Avanza. An abductive approach has been adopted to be able to analyse the studied subject and reach a conclusion. Conclusion: The thesis finds that the actions of the investigated individual investors can be divided into three categories. The ones that sold all their stocks when the stock market declined rapidly, the ones that didn’t do anything and the ones that bought more stocks successively. There is no clear connection between managing more money and getting less affected by psychological biases. Furthermore, the respondents were partly affected by how much earlier experience they had, whereas the ones with less experience were to a greater extent affected by psychological biases.