Del developed norms of behavioural data from two reading tasks (i.e., word accentuation and pseudoword reading) in adult Spanish speaking population in order to use them as estimates of premorbid intelligence quotient (PIQ) in brain injured, psychopathological, or cognitively impaired populations (Del Pino, R., Peña, J., Ibarretxe-Bilbao, N., Schretlen, D. J., & Ojeda, N. (2018). Demographically calibrated norms for two premorbid intelligence measures: The Word Accentuation Test and Pseudo-Words reading subtest. Frontiers in Psychology,9).In this commentary we discuss the adequacy to employ pseudoword reading (PWR) performance in Spanish as an estimator of PIQ. Current PWR level and scores on other reading tasks (e.g., irregular words reading) have been proposed as valid measures to estimate PIQ on the premiss that they correlate with IQ and show relative resistance to cognitive impairment derived from brain injury or illness. However, Del do not provide any direct evidence of the relationship between PWR in Spanish and PIQ. In what follows, we provide arguments that challenge the use of PWR performance in Spanish as an estimator of PIQ.First, Del claimed that "reading ability becomes, with practice, an automatic ability that is highly resistant to cognitive impairment" (p. 2), citing several studies in support.However, none of cited investigations addressed the PWR task. Del Ser et al. (1997) examined the ability of Spanish speakers to stress the correct syllable in a series of unfamiliar words. Harman-Smith et al. (2013) showed that performance in a reading task of irregular English words is a valid estimation of PIQ in patients with brain injury. Hessler et al. (2013) investigated the feasibility of a standardized multiple choice vocabulary test (i.e., the MWT-B, Lehrl, 1999) to estimate PIQ in cognitive impairment. Khandaker et al.`s (2011) meta-analysis examined the association between PIQ and the schizophrenia disorder, but no measurement of PWR was mentioned. Finally, Russell et al. (2000) investigated the validity of an irregular COMMENTARY ON DEL PINO 3 English words reading test (i.e., the National Adult Reading Test, NART; Nelson & Willison, 1991) as an estimate of PIQ in schizophrenia. In summary, the mentioned studies do not provide data related to the PWR task as an estimate of PIQ, while they do so for other word reading or vocabulary tasks, with mixed results.Del Pino et al. also claimed that "Concerning reading PW tests, the Spot-the-Word test (Baddeley et al., 1993) was proposed as an adequate instrument to assess premorbid IQ in older adults with normal aging as well as in patients with dementia (Friedman et al., 1992;Patterson et al., 1994;McFarlane et al., 2006)." (p. 2). Importantly, the Spot-the-Word (STW) test is not a PWR task but a lexical decision task (i.e., participants must identify the word in a pair of items comprising one word and one pseudoword). Friedman et al. (1992) demonstrated that the ability to read aloud a specific kind of unfamiliar pseudowords remains relatively preserved in patients with Alzheimer's disease (AD). The patients showed a poorer performance with the pseudowords that can be decoded exclusively on grapheme-phoneme correspondence (GPC) rules in comparison with the pseudowords that can also be read by analogy to alike words.Friedman et al. concluded that in the frame of dual-route reading models (e.g., Coltheart et al., 2001), AD patients are successful in PWR by developing automatic lexical-analogy mechanisms based on the lexical reading route and not through the GPC route. By contrast, Patterson et al. (1994) observed that PWR performance gradually declined across subgroups of AD at different (growing) levels of severity, even though all the employed items had conventional spelling patterns and rather word-like pronunciations.Differential effects in reading acquisition and adult reading have been found for languages that vary in the transparency of their spelling and in their metric systems (e.g., Seymour et al., 2003). Cross-language studies show that decoding skills (i.e., the application of GPC rules to letter and PWR) are learnt relatively early and with ease by normal child readers of transparent orthographies, while in languages with opaque orthographies these skills are established slower.Additionally, individual variability in decoding is much greater in opaque than in transparent languages (Seymour, 2005;Seymour et al., 2003), the relevance of decoding decreases with time (i.e., virtually all 5th-graders in transparent orthographies can master the GPC-rules (Burani et al., 2002;Jiménez-González & Hernández-Valle, 2000), and the reading experience favours the development of orthographic-lexical knowledge (e.g., Carrillo et al., 2013). From these results, we can conclude that 1) both reading effects observed and reading processes inferred in opaque languages, as English, cannot be directly generalized to other transparent languages, as Spanish; and 2) it is unlikely that PWR can reflect the engagement of cognitive skills needed to estimate the complex construct of IQ, at least in transparent orthographies.Moreover, the easiness of acquisition and mastering PWR in transparent orthographies cast doubts on its discriminant power.Del stated that several studies had criticized the use of the vocabulary test to estimate PIQ "…because vocabulary is known to decline with aging and is sensitive to brain damage" (p. 2); moreover, the authors pointed out that reading ability, when automatized, is "highly resistant to cognitive impairment" (p. 2). However, there is extensive literature that describes cases of acquired dyslexia after brain injury (Newcombe & Marshall, 1981). If vocabulary tests are not recommended to estimate PIQ because of their sensitivity to brain damage, PWR should not be employed in this quality either, at least for patients with a possible damage in the left temporal and parietal areas. Moreover, we should not obviate that developmental dyslexia is characterized by specific difficulties with PWR (Suárez-Coalla & Cuetos, 2015); importantly, this disorder has a considerable population prevalence of 10% (Jiménez et al., 2009;López-Escribano et al., 2018;Wagner et al., 2020).In summary, for some reason it has been assumed without sufficient evidence that PWR performance is an adequate estimate of premorbid PIQ. Furthermore, there is some reasonable COMMENTARY ON DEL PINO ET AL. ( 2018) 5 evidence suggesting that such an assumption is unlikely to be true, at least in Spanish and in other transparent orthographies.