When divided attention fails to enhance memory encoding. The attentional boost effect is eliminated in young-old adults

In the Attentional Boost Effect (ABE), images or words presented with to-be-responded target squares are later recognized more accurately than images or words presented with to-be-ignored distractor squares. Surprisingly, previous studies investigating the ABE have always examined young participants: thus, the question of whether this memory facilitation can be also observed in older adults has never been tested. The present study sought to fill this gap by examining whether healthy aging modulated the size of the ABE in 4 experiments in which the nature of the background stimuli (images vs. words), the length of the encoding trials (500 vs. 1,000 ms), and the type of instructions given to participants (incidental vs. intentional) were varied. In all cases, the results showed that the ABE was robust and significant in younger adults, whereas it was completely abolished in older adults. It is suggested that the detection of target squares required more attention resources in older than in younger adults, and that these resources were subtracted from the encoding of target-associated stimuli; thus, reducing or eliminating the ABE in the older group. Alternative explanations are also discussed.