The processing-speed theory of adult age differences in cognition

“…Among Processing Speed, Working Memory, and Inhibitory Control Processing speed, working memory, and inhibitory control have been hypothesized as cognitive primitives that explain age-related variation in episodic memory (Salthouse, 1985, 1996; Verhaeghen & Salthouse, 1997; Zacks & Hasher, 1994).”

“There are several possible explanations for this effect, including agerelated declines in perceptual speed (Salthouse, 1996) and attention-switching ability (Salthouse et al., 1998).”

“Furthermore, as processing speed and executive function are key cognitive domains known to be affected by the ageing process (Buckner 2004; Lezak et al. 2004; Salthouse 1996), the results support a phenomenon of ‘inflammaging’ which directly affects cognitive function.”

“Another is that speed of processing underlies developmental aspects of WM (Kail, 1993; Salthouse, 1996 ).”

“Kail and Salthouse [34], using Brinley plots [4] as a method to study cognitive aging [8,63], examined the extent of cognitive slowing in MS by fitting reaction time (RT) data of MS patients and healthy controls to the regression equation RTMS = a+bRTC which states that the mean RT of a group of MS patients will incre…”

“Alternative accounts of cognitive aging have suggested that more general or global mechanisms, such as slowed processing speed (Salthouse, 1996) or a general deterioration of neuronal integrity (Baltes & Lindenberger, 1997), mediate cognitive decline.”

“…involving BLOCKINspeed BLOCKINof BLOCKINprocessing BLOCKINand BLOCKINworking BLOCKINmemory; BLOCKINthis BLOCKINresult BLOCKINis consistent BLOCKINwith BLOCKINthe BLOCKINnotion BLOCKINthat BLOCKINaging BLOCKINis BLOCKINassociated BLOCKINwith BLOCKINslowing (Madden & Langley, 2003; Salthouse, 1996).”

“Associative and automatic processes may become more salient with age because of a strategic avoidance of more deliberative processing (Salthouse, 1996; Smith, 1996), shifts in motivation (Carstensen, 1995, 1998), or increased knowledge permitting reliance on gist (Adams, Smith, Nyquist, &…”

“…age differences in cognitive abilities such as reasoning, visuospatial ability, and episodic memory were mediated by hypothesized “processing resources,” such as information processing speed (Lindenberger, Mayr, & Kliegl, 1993; Salthouse, 1996) and working memory capacity (Salthouse, 1990).”

“First, age-related cognitive decline is common, and processing speed has been shown to play an early and central role in the cascading process that leads to many cognitive limitations [47-50].”

“Increasing age is correlated with decreases in cognitive abilities such as explicit memory, reasoning, and processing speed (Salthouse, 1996, 2000; Schaie & Willis, 1993).”

“The most dominant hypothesis has been the generalized slowing hypothesis, which states that all information processing is similarly affected by age (e.g., Birren, 1965; Brinley, 1965; Cerella, 1985, 1990, 1991, 1994; Fisk & Warr, 1996; Salthouse, 1985, 1996; Salthouse, Kausler, & Saults, 1988).”

“Age-related declines in perceptual speed may thus be responsible for not only decreases in the processing tasks of working memory but also age-related changes in cognitive performance in general (Salthouse, 1996).”

“These findings have given rise to the processing speed theory of cognitive aging, which asserts that normal agerelated decrements in the speed with which even simple cognitive processes are executed results in the gradual agerelated decline of more complex intellectual abilities (Salthouse, 1996).”

“, noisy, time-limited, attentionally demanding) conditions (3, 4).”

“The relatively large age effects on the LDST are in line with previous studies showing strong age effects on processing speed [9, 32].”

“For instance , Salthouse (1996) collected multiple empirical evidence that age-based changes in speed of information processing are a good or perhaps the best predictor of age-related changes in abilities from the fluid intelligence domain.”

“Although there is certainly interest in accounting for the myriad of age-related changes in cognition using a small number of variables (Lindenberger and Baltes, 1994; Salthouse, 1996), it is clear that there is a great deal of variability older adults' behavior across cognitive domains.”

“In light of the generally strong relations between intelligence and perceptual speed reported in the literature (e.g., Postuma, de Geus, & Boomsma, 2001; Salthouse, 1996; Sliwinski & Buschke, 1999; Verhaeghen & Salthouse, 1997; Zimprich & Martin, 2002), it would be useful to know whether there have been secular increa…”

“A similar view has been advocated in the developmental (Hale, 1990) and aging (Salthouse, 1996) literatures to explain age differences in cognitive processes.”

“…we speculate that the dysregulation in resting inhibition may play a role in a generic decline in central information processing capacity with increasing age (Salthouse, 1996) providing neurobiological support of the inhibition deficit theory of cognitive aging (Hasher and Zacks, 1988).”

“…commonly reported complaint in the context of healthy aging is that of cognitive decline – adults show reductions in processing speed, attentional resources, working and episodic memory, and inhibitory processing as they age (Craik and Byrd, 1982; Hasher and Zacks, 1988; Salthouse, 1996).”

“…in a number of different ways in cognitive aging, for example, as declining speed of processing (Myerson, Hale, Wagstaff, Poon, & Smith, 1990; Salthouse, 1996), declining capacity of working memory (Carpenter, Miyake, & Just, 1994; Park et al., 1996), and as a functional decline in working…”

“tasks, especially those related to learning and memory.(35,39) Therefore, improved processing speed could”

“A logically identical hypothesis is that age-related decline observed in all cognitive skills, including the solution of intelligence test problems, is entrained by slowing of elementary neuropsychological processes in old age (Hertzog, 1989; Salthouse, 1985, 1991, 1996, 1999, in press).”

“These brain changes are associated with declines in processing speed, executive functions, working memory (WM) and episodic memory (e.g., Salthouse, 1996; Baltes and Lindenberger, 1997; Park and Gutchess, 2002; Nilsson, 2003; Rönnlund et al., 2005; Hoyer and Verhaeghen, 2006).”

“The present results also support the literature indicating that processing speed is a key factor underlying more complex abilities in older children and adults (Salthouse, 1996).”

“For example, processing time was found to increase with age (Salthouse, 1996).”

“…influenced by cognitive speed is in line with previous findings (Salthouse et al., 2004) and corroborates the processing-speed theory of adult age differences by Salthouse (1996), which suggests speed as a key cognitive resource in older adults, even for a construct as multifaceted as PM.”

“As discussed in the Introduction, one potential problem in interpreting differences in task performance between TBI patients and healthy control concerns whether the impaired performance reflects anonspecificdeficit in patients, such as reduced processing speed (Ferraro, 1996; Salthouse, 1996), generalized inattention…”

“Whereas information processing capabilities tend to diminish with later age, especially processing speed (Salthouse, 1996; Verhaegen & Salthouse, 1997) the actual overall functioning of information processing changes very little in the course of one’s career (Ilmarinen, 2006).”

“Aging and the corresponding health-related declines in physical and cognitive function play an obvious role in reducing spare cognitive capacity (Salthouse 1996).”

“Perhaps the most expected age-related deficit in cognitive processing is in processing speed, with widespread slowdowns in basic cognitive and motor performance (Salthouse, 1996).”

“Furthermore, older adults need more time to process what they have heard because of slower cognitive functioning (Salthouse, 1996).”

“…with other higher-order cognitive processes such as working memory, prior research suggests that speed of processing is highly correlated with measures of executive function and memory, and mediates much of the age-related variance in cognitive performance (Park et al., 2002; Salthouse, 1996).”

“Some have argued that WM is material-neutral and equally applicable to all forms of verbal information (Engle et al., 1992; Just and Carpenter, 1992; Salthouse, 1996).”

“Although some analyses of more traditional test batteries have tended to report more consistent findings (Salthouse, 1996, 2000, 2005), it should be noted that even highly validated executive functioning tests may not correlate highly (Donders & Kirsch, 1991; Golden, Kushner, Lee, & McMorrow, 1998;…”

“Gs has been hypothesized to underlie individual differences in both Gf and Gsm (Jensen, 1999; Salthouse, 1996), and thus may contribute indirectly to chess skill through these factors.”

“This produces a general increase in information processing speed that allows subjects to perform a whole series of tasks more automatically and fluently (Salthouse, 1996).”

“But, this strategy is typically not as effective as the original performance— it just delays the inevitable decline that comes with age-related body and mind changes (Salthouse, 1996).”

“For example, it has been suggested that older adults’ difficulties stem from a general reduction in processing speed ( Salthouse, 1996 ), or from structural and functional changes in the prefrontal cortex (West, 1996, 2000); still others have argued that age-related changes in memory arise from a deficit in the abilit…”

“Indeed, onc of the hallmarks of cognitive aging has been generalized slowing of perceptual and cognitive operations (review: Salthouse, 1996).”

“The cross-out task is indicative of perceptual speed, which in old age is a sensitive marker of cognitive aging in general (e.g., Lindenberger, Mayr, & Kliegl, 1993; Salthouse, 1996).”

“of time and because of a reduced ability to process multiple concepts simultaneously [Salthouse, 1996].”

“These and other results (Madden, 2001; Salthouse, 1996, 2000) demonstrate that declines in processing speed, in particular, may play a key role in age-related deficits in performance.”

“The abundant literature on cognitive aging suggests that the decreases in processing speed is both indicative of and perhaps causally related to various deficits (Cerella, 1985; Hale & Myerson, 1995; Salthouse, 1996).”

“Via such effects, circulating blood lead could, for example, slow processing speed, which has been suggested to impair performance on cognitive tests (57).”

“in the speed of cognitive processing, the speed with which cognitive operations can be executed.(12,13) Cognitive processing speed in older adults has been associated with important cognitive operations such as episodic memory,(14,15) working memory,(16,17) reasoning abilities,(12,18,19) and verbal fluency.”

“For example, consider the generalized slowing hypothesis, a prominent hypothesis that has been widely accepted and attributes agerelated RT differences to a slowing with age in the speed of all cognitive processes or in the speed of a general mechanism that contributes to many cognitive processes (Cerella, 1985, 1990,…”

“One of the most prevalent theories in aging research is that a generalized slowing in brain function with age is responsible for most,if not all,of the age-related declines in problem solving, reasoning,memory,and language (Cerella,1990; Lindenberger & Baltes,1994; Salthouse,1985,1993,1996 ).”

“This explanation can be seen as reflecting general capacity models of aging, whereby increasing the number of cognitive components in a task increases the size of the age effect, possibly due to generalized slowing acting on all cognitive processes equally (e.g., Salthouse, 1996).”

“Many aspects of age-related cognitive decline show statistical overlap with measures of processing speed (Salthouse, 1994, 2000).”

“These cognitive functions (executive functioning (EF), attention and processing speed) decline with age [17,18] and if impaired increase fall risk [19].”

“Second, the three outcome measures (MMSE, Coding Task, and Raven Matrices) all indicate level of fluid intelligence, which is the ability to deal with new information (Salthouse, 1996).”

“A wide range of cognitive functions are susceptible to age-related decline, including vision (Johnson and Keltner, 1983; Klein et al., 1992), attention (Owsley et al., 1998), processing speed (Salthouse, 1996), hazard perception (Horswill et al., 2008), reaction time (Hultsch et al., 2002;)”

“Item scores were summed to produce a measure of information needs (7-35).”

“Kimberg and Farah, 1993), or by the decay of information before an operation is finished (cf. Hitch and Baddeley, 1976; Salthouse, 1996).”

“Both these basic abilities play a significant role in higher level functioning including comprehension, reasoning, planning and learning (Baddeley, 1992), and undergo change in normal child development and adult aging (Carpenter et al., 1990; Fry & Hale 1996; Kail, 1992; Salthouse, 1996).”

“Salthouse (1996) proposed a ‘simultaneity’ mechanism”

“Under general slowing theories (e.g., Salthouse, 1996, 2000; for a review, see Myerson & Hale, 1993), the speed of responding in cognitive tasks decreases with age regardless of the cognitive processes involved.”

“Older adults typically show slower processing speed, as compared with young adults (e.g., Salthouse, 1996 ), and there are typically no age differences in metacognitive monitoring.”

“The apparent requirement of additional time fixating the target prior to stepping may be a consequence of age-related decline in general visual function [12], slowed cognitive processing [13–15] and/or decline in visuomotor processing [16].”

“According to this alternative, differences in span performance are assumed to result from variability in the algorithms, or strategies, that individuals use while performing span tasks; moreover, the power of WM span tasks to predict variation in complex cognitive abilities may also derive from individual differences…”

“Other lines of research favor the idea of a particular cognitive function as the driving force behind age-related changes in other cognitive abilities, including working memory (Swanson, 1999) or a general speed function (Birren, 1974; Salthouse, 1985, 1996 ).”

“For example, students are typically 20 years old, while human capabilities to process information decline with age, with the best performance being in early twenties [47].”