![]() ![]() In support of this argument, contemporary studies using mechanical SRT measurements ( Montare, 2010 Eckner et al., 2011), including SRT testing procedures similar to those used by Galton ( Dordonova and Dordonov, 2013), report SRT latencies similar to those observed in the Victorian era. However, an alternative explanation of the apparent SRT slowing is that the SRT latencies reported in recent studies have been inflated by hardware and software delays in computer-based paradigms ( Dordonova and Dordonov, 2013). (2013) concluded that the slowed SRTs in recent studies reflected a systematic reduction in processing speed, and hence fluid intelligence, in contemporary populations. Given the correlation between SRTs and fluid intelligence ( Deary et al., 2001 Bugg et al., 2006), Woodley et al. These latencies are considerably shorter than those reported in recent SRT studies ( Lowe and Rabbitt, 1998 Deary et al., 2001 Deary and Der, 2005 Der and Deary, 2006). For example, in studies performed from 1884 to 1893, Francis Galton recorded visual SRT latencies that ranged from 181 to 189 ms in subjects ranging in age from 18 to 60 years ( Johnson et al., 1985). In a recent historical meta-analysis, Silverman (2010) found that SRT latencies have increased substantially since the Victorian era. Indeed, Jensen (2011) argued that SRT latencies provide one of the most objective metrics for comparing processing speed, and hence fluid intelligence, across different populations. More recent studies have shown significant correlations between SRT latencies of processing speed and measures of fluid intelligence ( Deary et al., 2001 Sheppard and Vernon, 2008). SRTs were first studied by Francis Galton in the late 19th century ( Johnson et al., 1985). Simple reaction time (SRT) tests, where subjects simply respond as fast as possible to the occurrence of a stimulus, are among the most basic measures of processing speed. Precise computer-based measurements of SRT latencies show that processing speed is as fast in contemporary populations as in the Victorian era, and that age-related increases in SRT latencies are due primarily to slowed motor output. SRT latencies increased with age while SDT latencies remained stable. ![]() Both SRTs and SDTs were slightly prolonged (by 7 ms). Experiment 2 tested 189 subjects ranging in age from 18 to 82 years in a different laboratory using a larger range of SOAs. SDT latencies averaged 131 ms and were unaffected by age. Stimulus detection time (SDT) was estimated by subtracting movement initiation time, measured in a speeded finger tapping test, from SRTs. As in previous studies, SRTs were prolonged at shorter SOAs and were slightly faster for stimuli presented in the visual field contralateral to the responding hand. Mean SRT latencies were short (231, 213 ms when corrected for hardware delays) and increased significantly with age (0.55 ms/year), but were unaffected by sex or education. ![]() ![]() Experiment 1 examined a community sample of 1469 subjects ranging in age from 18 to 65. We developed a calibrated and temporally precise SRT test to analyze the factors that influence SRT latencies in a paradigm where visual stimuli were presented to the left or right hemifield at varying stimulus onset asynchronies (SOAs). However, recent large-scale studies have reported substantially increased SRT latencies that differ markedly in different laboratories, in part due to timing delays introduced by the computer hardware and software used for SRT measurement. SRTs were first measured by Francis Galton in the 19th century, who reported visual SRT latencies below 190 ms in young subjects. Simple reaction time (SRT), the minimal time needed to respond to a stimulus, is a basic measure of processing speed. ![]()
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