  The Efficient Market Hypothesis (EMH) is widely accepted to hold true under
certain assumptions. One of its implications is that the prediction of stock
prices at least in the short run cannot outperform the random walk model. Yet,
recently many studies stressing the psychological and social dimension of
financial behavior have challenged the validity of the EMH. Towards this aim,
over the last few years, internet-based communication platforms and search
engines have been used to extract early indicators of social and economic
trends. Here, we used Twitter's social networking platform to model and
forecast the EUR/USD exchange rate in a high-frequency intradaily trading
scale. Using time series and trading simulations analysis, we provide some
evidence that the information provided in social microblogging platforms such
as Twitter can in certain cases enhance the forecasting efficiency regarding
the very short (intradaily) forex.
