What goes up, but never comes down?
If you guessed age, then you are absolutely right. Despite the significant advancements made in science, we have yet to reverse time or stop the process of aging (sorry anti-aging creams). As a result, many people suffer from a fear of getting old (known as Gerascophobia). But are our expectations for what happens to us when we get old valid?
An interesting Pew Research Center Social & Demographic Trends survey polled a large sample of 18-29 year olds about their expectations for old age. The survey showed that young people thought symptoms associated with old age, such as illness and memory loss, occur earlier and with greater frequency than older adults report actually experiencing. For example, 57% of young adults expect to experience memory loss by 65 and older, whereas only 25% of adults aged 65 and older actually report experiencing memory loss. Similarly, 45% of young adults expect to not be able to drive by 65 and older, whereas only 14% of adults aged 65 report difficulties driving.
This misalignment between young people’s expectations compared to older people’s experiences calls into question other areas that are generally assumed to be impacted by age, such as cognitive deficits.
Now of course, certain aspects of living do change as we age. We may have less endurance trying to keep up with the grandkids, or staying up past 9pm is just unfathomable. But in terms of cognitive decline, is there much basis for concern?
One area of cognitive control that is thought to be impacted by age is the inability to inhibit irrelevant information for the purposes of reaching a goal. This is known as the age-related inhibition deficit. An inhibition deficit, or inability to ignore irrelevant information, creates problems for activities that require focused attention while ignoring distractions, such as driving. Interestingly enough, although some studies provide evidence of an inhibition deficit in older adults, there are a number of studies that do not.
In a recent article published in Psychonomic Bulletin and Review, Alodie Rey-Mermet and Miriam Gade sought to reconcile this inconsistency of age-related inhibition deficits reported in the literature. The researchers conducted a meta-analysis (that is, a summary statistical evaluation of studies published on similar topics) to evaluate what is preserved and what declines during aging.
Specifically, Rey-Mermet and Gade compared a large number of studies that measure inhibition in older adults using various cognitive tasks. To illustrate, consider the Color Stroop task, where participants are shown a color label presented in a color font (e.g. the word “red” in blue font) and are asked to name the color of the font as quickly as possible:
This task measures the ability to inhibit the reading of the color label which is irrelevant to the goal of correctly identifying the font.
The benefit of using data from a large number of tasks in a meta-analysis is that differences in inhibition between older and younger adults that are task-dependent can be elucidated. See the table below for a list and description of the inhibition tasks used:
Below are demonstrations of some of the other tasks used in these studies:
In all the tasks, participants were required to respond as quickly as possible and responses were either correct or incorrect. For example, in the Stroop task, participants had to correctly name the color of the font as quickly as possible. This resulted in two performance measures, reaction time and accuracy (i.e., the proportion of correct responses). Importantly, all tasks were carried out on samples of both young and older adults to evaluate performance differences due to age.
To determine if there were age-related deficits in control, Rey-Mermet and Gade examined whether the data from a baseline condition (in the Stroop task, this refers to a condition in which color of the font and the word meaning are identical) and the data from the interference condition (the word “red” in blue font) could be described by the same regression line when performance of the older adults is plotted on the y-axis and that of the younger participants on the x-axis.
If a single regression line fits the data, this would suggest no selective interference-related deficit for the older participants. Conversely, if two separate lines are required to fit the data, then this would suggest a selective decline of cognitive control as a function of age. The figure below illustrates the idea with synthetic data. In each panel, each plotting symbol represents data from one condition in one experiment, with performance of the old participants plotted on the y-axis and that of the young participants on the x-axis. The blue symbols plot the baseline conditions from the various experiments whereas the red crosses refer to the corresponding interference conditions. If the data end up looking like the left panel, then there is no evidence for an age-related deficit in cognitive control. If the data look like the panel on the right, by contrast, then one would infer that older participants were particularly disadvantaged by the interference, beyond a general slowing that might also be observed in the baseline condition.
The results from the meta-analysis demonstrated that in some tasks, older adults displayed an impaired ability to inhibit irrelevant information (i.e. Stop-signal Task and the Go/No-Go Task); however, in other tasks, this deficit was not observed (i.e. Color Stroop Task, Color-Word Stroop Task, Flanker Task, Local Task, and the n-2 repetition costs task).
See the table below for the complete set of results, encapsulated by the pithy summaries in the right-most column:
Taken together, it appears that the age-related inhibition deficit is not as clear-cut a case as was once hypothesized. A considerable number of studies failed to support the deficit with age, which suggests that further work needs to be done to validate the age-related inhibition deficit hypothesis.
In other words, we can all breathe a little easier, given that the verdict is still out on this one. There are a plethora of things we can worry about while getting order, but at the moment, inhibition deficit is not one of them.
Featured Psychonomic Society article:
Rey-Mermet, A., & Gade, M. (2017). Inhibition in aging: What is preserved? What declines? A meta-analysis. Psychonomic Bulletin & Review, DOI: 10.3758/s13423-017-1384-7.