This[1] is the paper they quote. The paper is pretty confused, mostly by their own fault. For example:
Recent evidence shows that whereas short-term memory for names and inverted faces peaks around the age of 22 years, neither short-term memory for faces nor quantity discrimination peaks until around the age of 30, a fact difficult to assimilate into the fluid-/crystalized-intelligence dichotomy (Germine, Duchaine, & Nakayama, 2011; Halberda, Ly, Wilmer, Naiman, & Germine, 2012). Whether face memory and
quantity discrimination are exceptions to the fluid/crystalized rule or represent more systematic and previously unrecognized patterns of age-related difference is an open question
First, there's no "fluid-/crystalized-intelligence dichotomy", since the two factors are highly correlated with each other, to the point where psychometricians prefer to derive the higher-order order factor, g.
Second, clearly the authors will be very confused by results like this if they don't actually calculate g-loadings, and at the very least correlate the vector of g-loadings with the vector of age declines.
Now compare the above paper with a paper studying basically same question, but using proper factor analysis[2]. In particular, if you're low on time or background, look at the graphs in Fig 2. Clearly, being able to separate g-loading from group factors and test-specific measurement error gives us much clearer picture of age-related decline.
Recent evidence shows that whereas short-term memory for names and inverted faces peaks around the age of 22 years, neither short-term memory for faces nor quantity discrimination peaks until around the age of 30, a fact difficult to assimilate into the fluid-/crystalized-intelligence dichotomy (Germine, Duchaine, & Nakayama, 2011; Halberda, Ly, Wilmer, Naiman, & Germine, 2012). Whether face memory and quantity discrimination are exceptions to the fluid/crystalized rule or represent more systematic and previously unrecognized patterns of age-related difference is an open question
First, there's no "fluid-/crystalized-intelligence dichotomy", since the two factors are highly correlated with each other, to the point where psychometricians prefer to derive the higher-order order factor, g.
Second, clearly the authors will be very confused by results like this if they don't actually calculate g-loadings, and at the very least correlate the vector of g-loadings with the vector of age declines.
Now compare the above paper with a paper studying basically same question, but using proper factor analysis[2]. In particular, if you're low on time or background, look at the graphs in Fig 2. Clearly, being able to separate g-loading from group factors and test-specific measurement error gives us much clearer picture of age-related decline.
[1] - https://sci-hub.tw/10.1177/0956797614567339 [2] - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3637652/