Episodic intertrial learning of younger and older adults: Effects of word frequency

Abstract

Older adults have a demonstrable episodic memory deficit. The present study aimed to investigate whether the age deficit in episodic memory was influenced by stimulus characteristics known to produce differences in memory performance in younger adults, specifically word frequency. An intertrial paradigm was used whereby participants studied high- or low-frequency lists over several study-test trials, and the loss and gain of individual items was measured across trials; putative measures of consolidation and encoding. The results show that high-frequency words are recalled significantly better than low-frequency words. Older adults acquired high-frequency words at a greater rate across trials than they did for low-frequency words, an effect not evident in the younger adults. Older adults were found to have deficits in both encoding and consolidation as measured by losses and gains of items across trials. The results support the inter-item association theory of the word frequency effect on recall, with the age differences suggesting that memory deficits are sensitive to stimuli characteristics - one interpretation being that the ease of processing of the stimuli at encoding facilitates later recall.

Differences in learning rates for item and associative memories between amnestic mild cognitive impairment and healthy controls

“…In addition, although there is no significant difference in word frequency and age of acquisition between the two tests, Almond et al (2013) [20] found that high-frequency words are learned at a higher rate than low-frequency words in older adults compared to younger adults, which indicates that the memory deficits may be modulated by word frequency. However, the number of words used in the present study is too limited to be separated into high and low frequency words for further statistical analysis.…”

“…This can be deduced from the slope of the learning curve in multiple learning trials. Learning rate has been found to be sensitive to age-related memory deficits and even to stimuli characteristics (word frequency) in older adults [20]. People with cerebral lesions in different brain locations also showed different learning rates [21].…”

“…Thus, a meaningful method to investigate learning rate is to consider intertrial performance, i.e., the examination of the items that are gained and lost on multiple repeated trials [12,20,22]. Trial-by-trial performance can be analyzed according to gained access (GA; the proportion of items recalled on trial n + 1 out of those that were not recalled on trial n ) and lost access (LA; the proportion of items not recalled on trial n + 1 out of those that had been recalled on trial n ) [20,26].…”

“…Trial-by-trial performance can be analyzed according to gained access (GA; the proportion of items recalled on trial n + 1 out of those that were not recalled on trial n ) and lost access (LA; the proportion of items not recalled on trial n + 1 out of those that had been recalled on trial n ) [20,26]. GA mainly reflects intertrial acquisition and can be presumed to be a function of the degree to which a representation of an item in memory is strengthened during a particular study trial.…”

“…We would acknowledge here that in addition to acquisition and consolidation, retrieval may also contribute to both GA and LA e.g. [12,20] and two variables of GA and LA may not be mutually exclusive. Nevertheless, following Almond et al (2013) [20], we shall accept the general consensus that acquisition and consolidation account for the majority of GA and LA, respectively.…”