If your memory's been telling you that you've done things you haven't actually done, you're not alone. A team of German researchers has published a study that suggests this type of false memory may occur fairly often. Watching someone perform an action may leave the false impression that you've done it, too.

Single men do not attend a wedding, come home to an empty house and wonder where their wife's gone off to. But a week after the wedding, they might remember kissing the bride, even though they didn't.

There's no indication that people get confused about the big things in life. Single men do not attend a wedding, come home to an empty house and wonder where their wife's gone off to. But a week after the wedding, they might remember kissing the bride, even though they didn't.

It's been known for some time that imagining performing an action can later on leave a false memory of actually having performed that action. The study researchers were interested in testing whether watching people perform an action could also leave false memories behind.

The researchers had study subjects perform some rather mundane tasks, such as shaking a bottle or shuffling a deck of cards. The subjects then watched videos of other people performing tasks — some of which they had performed themselves, some of which they had not.

Two weeks later, the participants took a memory test. The test revealed that they were much more likely to remember performing an action they hadn't performed if they had watched a video of someone else performing that action.

The researchers repeated the experiment, warning participants about the effect and reminding them to guard against it. But the results were the same. They call the phenomenon observation inflation and believe that the process occurs unconsciously.

When it comes to memory, seeing it may mean believing that you've done it.

Now it may be asking a lot to expect someone to recall what trivial actions they did and did not perform two weeks ago. Some people even have difficulty remembering what month it was two weeks ago. It will take further research to determine if observation inflation and the false memories that it leaves behind act over a shorter time span. If they do, it could mean that just watching someone else perform a trivial daily activity, such as picking up the mail, could make others falsely remember having picked up their mail.

Or, watching someone else take their medication might make a person think later on that they've taken their own medication. Which is far from trivial.

Are you sure you turned off the car lights?

An article detailing the study was published in the September 2010 issue of the journal Psychological Science.