The fascinating reason you forget what you’re doing when you walk into a room – it doesn’t mean you have dementia

We’ve all walked into a room only to find that the reason for doing so has suddenly and entirely vanished from our mind.

Experts have revealed that these so-called ‘brain farts’ are not anything to be concerned about — in fact, they are the result of a perfectly normal brain response to new surroundings.

Specifically, it is a phenomenon called the ‘doorway effect’, according to ​Christian Jarrett, a cognitive neuroscientist and writer. 

It happens because our brain naturally compartmentalises activities and information, based on environmental contexts, such as rooms or specific places. 

The brain ‘resets’ slightly when moving between rooms, Jarrett told BBC Science Focus, causing information thought of while in the previous room to slip out.

Jarrett pointed to the findings of a University of Queensland study that explored the doorway effect.

‘They found that passing through doorways that joined identical rooms mostly didn’t impact memory – perhaps because there wasn’t enough of a changed context to create a significant event boundary,’ he said.  

‘It was only when these researchers distracted their volunteers with a simultaneous secondary task that the doorways between identical rooms affected memory.’

The effect is much more likely, he posed, when there is a significant change in context – for instance, if you leave your living room for the garden.

He continued: ‘The Queensland team said this chimes with everyday experience in that it’s mostly when we’re distracted, with our mind on other things, that we’re inclined to arrive in a room and forget what we came for.’

Jarrett added that the findings may also point to a potential hack that may prevent the problem. 

‘Try to stay focused on your purpose when you pass through a doorway on an errand,’ he said, adding that it may be useful to make a note on the back of your hand.

Jarrett’s comments echo the findings of a team of scientists from the University of Notre Dame in Indiana who, in 2016, conducted an experiment that shed light on the brain’s ‘filing cabinet’ system.

The researchers argued that events and memories are ‘filed away’ from one room as soon as we exit into another, storing information in successive chapters or episodes.

Doorways act as a kind of trigger for this process, according to the study, published in the Quarterly Journal of Experimental Psychology.

A team of US researchers asked volunteers to use computer keys to navigate their way through 55 ‘virtual’ rooms, large and small. 

Each room contained one or two tables, with objects that the volunteers had to pick up, carry to the next room and set down on a table again. 

As soon as they picked them up, the objects disappeared.

Throughout the test, they were presented with the name of an object and asked if it was the one they were currently carrying, or the one they had already put down.

The results showed memory performance dipped markedly once they had passed through a doorway, rather than when they covered the same distance but remained in the same room.

To confirm the findings in real life, rather than on a computer, the team set up a similar environment of rooms and tables – hiding the objects in boxes the volunteers carried.

Again, the researchers found participants were more likely to forget what they had in the box once they walked through a door into the next room.

In a report on their findings, researchers said that moving into a new environment probably clutters the brain’s working memory, so that it cannot recall the original reason for entering a room. 

The report stated that the extra information ‘overloads and adds more and more information to the working memory’.