The processing-speed theory of adult age differences in cognition

“This is particularly important given that many aspects of speeded performance show a monotonic decrease across the life span (Salthouse, 1996).”

“For illustration, let us consider the two mechanisms proposed by Salthouse (1996) to describe the assumed effect of age-related slowing on cognition, the limited time mechanism and the simultaneity mechanism.”

“Another thoroughly researched theory of cognitive aging and agerelated decline in fluid abilities is the processing speed hypothesis (Birren, Woods, & Williams, 1980; Salthouse, 1996).”

“Second, as suggested by the literature on generalized slowing of cognitive processing (e.g., Salthouse, 1996) stream segregation in the presence of energetic and informational masking may take a longer time to emerge in older than in younger adults.”

“…nature and extent of processing required for successful task performance (e.g., Cerella, 1990; Hale, 1990; Kail & Salthouse, 1994; Myerson, Hale, Wagstaff, Poon, & Smith, 1990; Salthouse, 1996, 2000; Salthouse, Fristoe, McGuthry, & Hambrick, 1998; for a review see, e.g., Bashore & Smulders, 1995).”

“Previous research showed that increasing age is associated with reduced working memory and processing speed (Salthouse 1996; Schaie 2005), as well as failures in prospective memory enabling the remembering and initiation of future intentions (Kliegel, Jäger, and Phillips 2008).”

“to memory, executive function, processing speed, attention, and spatial ability have also been shown to deteriorate with age [14–19].”

“Second, research suggests that older adults may have fewer cognitive resources available as compared with younger adults (Park, 1999; Salthouse, 1996; Salthouse & Babcock, 1991; Schaie, 1994).”

“Overall reduced processing speed in older adults (Salthouse, 1996), a key target group in clinical neuropsychology, may thus seriously lower the validity and complicate the interpretation of the performance on either speeded stimulus presentation or reaction times as outcome measures.”

“Several aging theories have already proposed that age-related decreases in basic cognitive processes, such as working memory and processing speed, underlie declines in more complex cognitive functions, such as language or decision-making (Hasher & Zacks, 1988; Salthouse, 1990, 1996).”

“Salthouse[132] delineated the hypothesis that a basic parameter such as speed is directly related to biological factors and is essential for higher order cognitive processing.”

“It is also the case that older adults show systematic slowing in many aspects of behavior (Salthouse, 1996).”

“It does not appear to be part of a broader problem in fluid intelligence (often associated with processing speed, Salthouse, 1996; Jensen, 1998), as controlling statistically for performance IQ had little impact on observed group differences.”

“For example, older adults are slower (Salthouse, 1996) and have reduced working memory capacity relative to younger adults (Dobbs & Rule, 1989).”

“Integration is also important in some accounts of task complexity based on speed: Speed may be important in complex tasks because combining the results of different task operations requires that they all be available at the same time (7).”

“…age-related change in top-down effects, we also assessed the degree to which the age differences in search RT could be attributed to attention specifically, rather than to a more generalized effect of age-related slowing of elementary perceptual processing (Madden, 2001; Salthouse, 1996, 2000).”

“Many of these have focused on fairly general explanations for this loss, such as reduced executive or working memory resources (see Light, 1991, for a review), and/or reduced processing speed (Salthouse, 1996).”

“Speed of processing refers to processing efficiency or rate (Kail and Salthouse 1994, Salthouse 1996 ) and emphasizes the amount of cognitive work that can be completed in a given unit of time.”

“…underlies age-associated decrements in other higher-order cognitive functions including memory and executive functioning (Hedden, Lautenschlager, & Park, 2005; Levitt, Fugelsang, & Crossley, 2006; Rabbitt et al., 2007; Salthouse, 1996, 2005; Salthouse & Coon, 1993; Salthouse & Ferrer-Caja, 2003).”

“In order to test the possibility that detected overlaps in EF and intelligence are simply attributable to shared dependence on processing speed, itself a strong correlate of intelligence (Salthouse, 1996), we also test whether these associations are robust to controls for a latent speed factor.”

“, [49-54].”

“including psychology [43,49], organizational behavior [e.”

“Several studies have focused attention on age-related differences in reading comprehension trying to identify which differences in the general mechanisms, such as working memory, inhibition, and processing speed, could explain the age-related changes (Salthouse, 1997).”

“Furthermore, the speed of response is associated with focussed and sustained attention (Salthouse, 1996, 2000; Verhaeghen & De Meersman, 1998).”

“Information processing speed, and hence gspeed, decreases with age and may therefore provide a useful indicator of cognitive decline in later life (Deary et al. 2010; Ritchie et al. 2014; Salthouse 1996; Verhaeghen 2014).”

“Salthouse (1996) proposed that older adults have limited resources to perform complicated cognitive tasks and they may be particularly sensitive to the demands of simultaneous tasks (Brouwer, Waterink, Van Wolffelaar, & Rothengatter, 1991).”

“In previous studies, Salthouse preferred to adopt general slowing to explain age-related decline in cognition, and assumed that processing speed is a primitive construct that influence the cognitive system without themselves being reducible to other psychological constructs (Salthouse, 1996; Verhaeghen & Salthouse, 19…”

“Salthouse [23], argues that processing speed can account for both: (1) other cognitive deficits, and (2) functional deficits.”

“This view is consistent with that of Salthouse (1996), who concluded that an age-related deficit in IPS is one of the major causes of cognitive decline in the elderly.”

“Salthouse et al. (2004) found evidence of a prospective memory construct in 330 adults between 18 and 89 years of age using four measures of event-based prospective memory.”

“The most pervasive change with developmental aging is reduced performance on most cognitive tasks in which speed of response is a factor (Salthouse, 1996).”

“This is consistent with knowledge that there is a strong age-associated decline seen in performance on speeded tasks [34; 35].”

“We estimated processing speed using the simple ASVAB tests of coding speed and computation speed, which have been widely used in similar research (Kail, 1991; Salthouse, 1996).”

“The delayed parietal P3 with a decreased amplitude in older adults has been interpreted as evidence of cognitive decline [41–43] due to neural decrements in posterior brain regions.”

“Since Vz also reflects speed of processing information (Salthouse, 1996), this might have affected speed of encoding the SAT problems, such that high Vz subjects were able to execute the relevant mental operations faster resulting in the significant time difference between high- and low-Vz subjects.”

“Adding both a measure of perceptual motor speed (digitsymbol coding time) and acuity as predictors before age group, however, indicated that most (.829) of the age-related variance in the accuracy slopes was shared with these other two variables (Madden, 2001; Salthouse, 1985, 1996 ).”

“Aspects of memory (4, 10, 12), attention (1, 12, 40), executive functioning (12, 58, 60), and processing speed (59) are typically [but not always (37, 48)] impaired with advancing age.”

“At the same time, there is also evidence of declines in perceptual speed and memory in old age, and recent evidence suggests that declines in measures of cognitive performance in the older age ranges are probably linked to declines in processing and sensory abilities (Salthouse, 1996).”

“The five tests were (a) word-list recall (Lezak, 1995), scored as the sum of immediate- and delayed-recall items; (b) a backwarddigit-span measure of working memory (Wechsler, 1997); (c) a category-fluency measure of verbal fluency (Lezak, 1995); (d) an inductive-reasoning measure of fluid intelligence (Salthouse & Pr…”

“Other views of cognitive ageing emphasise age changes in the capacity or speed of information processing (e.g., Craik, 1986; Salthouse, 1996), our view focuses the importance of eYcient processing, such that attention is occupied only by information relevant to accomplishing current goals.”

“In particular, the processing-speed theory of adult age differences (Salthouse, 1996) emphasizes that elementary cognitive operations appear to slow with age, leading to pervasive effects on the WM system and fluid cognition (see also, Birren & Fisher, 1995; Kail & Salthouse, 1994; Lindenberger,…”

“…times have been suggested to capture reliable individual differences in search (Dougherty and Harbison, 2007), any reaction-time based measure poses interpretational problems regarding exploratory tendencies with aging due to overall age differences in motor and cognitive speed (Salthouse, 1996).”

“Existing work on the development of reasoning has focused on individual differences in its trajectory over time (McArdle, Ferrer-Caja, Hamagami & Woodcock, 2002) or on relations to other facets of cognitive ability (Fry & Hale, 2000; Conway, Cowan, Bunting, Therriault & Minkoff, 2002; Salthouse, 1996; Salthouse, Babco…”

“As a measure of cognitive ability, we focus on perceptual speed, based on the following considerations: First, reduced perceptual speed is regarded as a powerful indicator of cognitive decline in aging (Finkel et al., 2007, Lindenberger et al., 1993, Salthouse, 1996, 2000).”

“For example, it is possible that processing speed precedes and brings about the changes in memory (Birren, 1974; Salthouse, 1996).”

“The processing speed theory of cognitive aging (Salthouse, 1996) proposes that age-related declines in cognitive function (e.g., WM performance) stem from slowed processing operations.”

“However, it is not yet clear how much each of these factors contributes to the effect of ageing on cognition (see, for example, Kwong See & Ryan, 1995; Park et al., 1996; Salthouse, 1996; Van der Linden et al., 1999).”

“Thus, we computed the total variance in the difference measure as explained by age, and then determined what proportion of this total age-related variance was explained uniquely by age after partialing out the age-related variance in basic processing speed (following the statistical control procedures suggested by Sal…”

“speed often explains a significant amount of age-related variance across a variety of cognitive domains (Salthouse, 1996), although a single-mechanism model is unlikely to fully account for age effects in skill retention (e.”

“…in the typical aging literature suggest that cognitive aging can be observed after 50 years of age with declines observed in processing speed (Salthouse, 1996); attention (McCabe et al., 2010), metacognitive ability (Mäntylä et al., 2010), executive functions (Craik & Bialystok, 2006;…”

“The most documented cognitive changes in the aging brain are slower processing speed (Salthouse, 1996), poor encoding of information into episodic memory (Balota et al., 2000) and a deficit in inhibitory processing (Kramer et al., 1994).”

“Thus, sleep pressure-related slowing in the young “makes them old”, while older people, notwithstanding cognitive slowing [133], are less susceptible to circadian and wake-dependent performance decrements.”

“This process may potentially contribute to motor and cognitive slowing [53] that has been suggested as fundamental to agerelated cognitive decline [54].”

“Disruption of any of these cognitive abilities, either as a function of normal cognitive aging (Dodge et al., 2006; Salthouse, 1996) or of a dementing disorder (Okonkwo et al.”

“In selecting our sample, we only included young adults 20–41 years of age given the existence of age-related changes in neurocognitive function for middle-age participants (Houx, Jolles, & Vreeling, 1993; Houx, Vreeling, & Jolles, 1991; Salthouse, 1996).”

“Nonetheless, the general slowing theory of cognitive ageing is very influential (Salthouse, 1996; Verhaeghen & Salthouse, 1997) and given that Miyake et al.”

“Therefore, the standardized score from this single component (the unrotated first principal component) was used as the AVLT memory score. was used as an indicator of speed of information processing (Salthouse, 1996).”

“Gains in processing speed increase the amount of information that can be mentally manipulated and the complexity of such manipulations [2–4].”

“Some of these deficits may be “downstream” effects of a loss in speed of processing, which begins during the third decade of life (Salthouse, 1996, 2000), or they may result from declining exec- utive skills.”

“…in cognitive processing experienced by older adults in general, and memory in particular, are reductions in attentional or working memory capacity (Baddeley, 1986; Craik, 1986), slowed speed of processing (Salthouse, 1996) and lack of inhibitory control (Hasher & Zacks, 1988; Hasher et al., 1999).”

“Cognitive aging may be normatively characterized in terms of declines in basic processing capacities (e.g., declining speed, Salthouse, 1996; or working memory, Carpenter, Miyake, & Just, 1994).”