An enduring question for many of us is how relevant our laboratory experiments are for the "real world". In a paper now out in Experimental Aging Research we took a small step towards answering this, in work that Caitlin Ward did as part of her senior honors project a couple of years ago. In this study, participants listened to short stories (Aesop's fables); after each story, they repeated it back as accurately as possible.
We scored each story recall for accuracy, sitting apart scoring for different levels of narrative detail (as frequently done in so-called propositional scoring approaches). The stories were presented as normal speech (acoustically clear) or as noise-vocoded speech, which is lacking in spectral detail. We predicted that the vocoded speech would require additional cognitive processes to understand, and that this increased cognitive challenge would affect participants' memory for what they heard—something that we often care about in real life.
We found that recall was poorer for degraded speech, although only at some levels of detail. These findings are broadly consistent with the idea that acoustically degraded speech is cognitively challenging. However, it is important to note that the size of this effect was relatively small: recall was only 4% worse, on average, for the challenging speech. The small effect size suggests that listeners are largely able to compensate for the acoustic challenge.
Interestingly, we also found that a listener's verbal short-term memory ability (assessed by reading span) was correlated with their memory for short stories, especially when the stories were acoustically degraded. Both young and older adults show a fair amount of variability in their short term memory, so it seems this correlation is more reflective of a cognitive ability than a simple age effect.
Hearing ability—measured by pure tone average—was not significantly related to recall performance, although there was a trend towards participants with poorer hearing showing worse recall.
One side note to this study is we have provided all of the sound files used in the experiment through our lab website, and I've referenced the github repository that includes my vocodong scripts. One step closer to fully open science!
This article appears as part of a special issue of Experimental Aging Research that I edited in honor of Art Wingfield, my PhD supervisor. There are a number of interesting articles written by folks who have a connection to Art. It was a lot of fun to put this issue together!
Ward CM, Rogers CS, Van Engen KJ, Peelle JE (2016) Effects of age, acoustic challenge, and verbal working memory on recall of narrative speech. Experimental Aging Research 42:126–144. doi:10.1080/0361073X.2016.1108785 (PDF)