In Hattrick, overconfidence is an event that happens when a team severely underestimates their series opponent and thus performs worse than it normally would. This usually happens when a team leading the series is playing a team in the bottom part of the table; the event can happen for any league game from the second week until the last game of the season. Overconfidence does not happen in cup or friendly matches.
The overconfidence check is done once before the match; if there is overconfidence, there will be a message about the players' attitude before the match begins. The affected teams midfield rating is reduced an estimated 15-20%. It is possible for the coach to amend the effects of overconfidence during the match break; if so, there is a mention in the match report at the beginning of the second half. However, this can only happen if the overconfident team is losing at half time.
Based on some research, overconfidence can happen when a team with a strong or better confidence plays a team at least five places below it in the series table (i.e. 1st vs 6-7-8th, 2nd vs 7-8th, and 3rd vs 8th). It is not known whether there is a higher chance for overconfidence to happen when the potentially overconfident squad plays PIC, but what is known is that it cannot happen when that potentially overconfident squad plays MOTS. It is not clear yet whether winning streak is a factor, or if the number of sports psychologists is, although HT-Tjecken explained on Global that psychologists should be fired in cases where possible overconfidence can lead to problems:
Q: So overconfidence can happen more often. To prevent it I should hire the maximum number of psychologists, not fire them?
A: Psychologists boost your confidence, they're not at all useful to lower it. So I should sack them in case of overconfidence and not hire more.
However, it is perfectly possible for overconfidence to happen with no psychologists hired at all neither the week of the match nor the week before.
In some cases, overconfidence is not much of a problem because the winning team would win anyway; sometimes, however, an overconfidence event could decide to whom goes the series medal. Teams so affected decry their luck.
There are several confidence levels listed in the Denominations that sound like the team is acting overconfident (slightly exaggerated, extremely exaggerated and completely exaggerated), however, for some reason these never appear on the web pages nor in the XML files downloaded by CHPP applications. It might be related to such confidence levels being only reached while matches with overconfidence events are played, but due to the fact that team data is unavailiable to download while matches are played, and the web pages hide confidence at that time, these denominations stay pretty much unused.
The previous paragraph stood before the 30th season changes; it is yet to discover how this will work in the season to come.