This study, using a sample of New Zealand investors, investigates three behavioural finance theories: investor overconfidence, socialization and the familiarity effect. We find support for the investor overconfidence theory, using characteristics such as past success, optimism, confidence in one's abilities, investment experience and investment-related knowledge. Concerning the socialization theory, we observe that the investors actively sought information regarding the stock market, 75 per cent doing this on a weekly basis. Those investors that kept themselves informed daily outperformed other investors by 8 per cent. The familiarity effect was confirmed, showing investors to hold a far too high proportion of local stocks, although the majority of investors believed international equity markets would provide returns that were either better or equal to New Zealand stocks.