Thursday, November 20, 2014

Memory, Aging, and Distraction

The population in the United States is aging.  That has created a lot of anxiety about the cognitive effects of getting older.  Lots of research suggests that older adults are worse than younger adults on a variety of different thinking tasks.  They remember fewer words from lists they see.  They are slower to respond in many situations.  They have more trouble ignoring distracting information. 

An interesting paper in the April, 2013 issue of Psychological Science by Renee Biss, Joan Ngo, Lynn Hasher, Karen Campbell, and Gillian Rowe suggests that—while these factors may look like they are all aspects of cognitive decline—there are times when these changes may actually be helpful.

In particular, there has been a long line of research in psychology showing that older adults have worse basic recall memory than younger adults.  The typical way to demonstrate this effect is to show participants a list of words and then have them recall the words from that list after a short delay.  College students remember a higher proportion of the words on the list than adults in their 60s and 70s.

The researchers in this study speculate, though, that in many situations there may be subtle reminders of what needs to be remembered in the world.  If older adults pay more attention than younger adults to information that may seem distracting, then that may actually help their memory.

To test this possibility, college students (with an average age of about 20) were compared to older adults (with an average age of about 68.  First, participants saw a list of 20 words that they were told to remember for later.  After a brief delay in which everyone counted backward by 3s starting with the number 74, participants were asked to remember as many words as possible from the list.

After that, participants did a 1-back test. In a 1-back test, a series of pictures are shown, and participants respond with one key when the current picture was identical to the previous picture and with a second key when the current picture was different from the previous picture.  The pictures in this test were all line drawings of objects that were not related to the words that were studied.

On each trial, though, there were words superimposed on the pictures in a different color than the line drawing.  Participants were told that the words were irrelevant to the task and that they should be ignored.  However, eight of those words were items that had actually been presented on the study list.  After doing this 1-back test, participants were asked to recall the list of words again. 

On the initial test, the older adults recalled significantly fewer of the words from the list than the younger adults.  After the 1-back test, older adults recalled more words that had been shown in the 1-back task than words that had not been shown.  In fact, they remembered just about as many of those repeated words as younger adults did.  The younger adults were not affected by the 1-back test.  They remembered words equally well regardless of whether they were repeated in the 1-back test.  In fact, the older adults remembered the repeated words just about as well as the younger adults did, allowing them to overcome the age difference in memory.  Overall, people recalled a little over 30% of the items from the list, so this is not a ceiling effect.

One other interesting finding in this study was that older adults responded slightly more slowly to the pictures when the accompanying word had appeared on the initial list than when it had not.  Younger adults showed no difference in speed to respond to these items.  This finding suggests that older adults were more distracted by items they had seen before than younger adults.  None of the participants included in the analyses explicitly recognized that words from the list had appeared in the 1-back test, so this distraction was happening without awareness.

This research replicates previous work showing that older adults remember less and are more distractible than younger adults.  However, this work also suggests that there is a silver lining to this combination.  If older adults need to remember a piece of information, they may be more likely than younger adults to notice information in the environment that helps them to remember it.  This combination may help them overcome some of their memory limitations.