Visual letter search performance was investigated in a group of dyslexic adult readers using a task that required detection of a cued letter target embedded within a random five-letter string. Compared to a group of skilled readers, dyslexic readers were significantly slower at correctly identifying targets located in the first and second string position, illustrating significantly reduced leftward facilitation than is typically observed. Furthermore, compared to skilled readers, dyslexic readers showed reduced sensitivity to positional letter frequency. They failed to exhibit significantly faster response times to correctly detect target letters appearing in the most, compared to least, frequent letter position within five-letter words, and response times correlated with positional letter frequency only for the initial, and not the final, letter position. These results are compatible with the SERIOL (sequential encoding regulated by inputs to oscillations within letter units) model of orthographic processing proposed by Whitney and Cornelissen (2005). Furthermore, they suggest that dyslexic readers are less efficient than skilled readers at learning to extract statistical regularities from orthographic input.
BatesE.ElmanJ. (1996). Learning rediscovered: A perspective on Saffran, Aslin, and Newport.Science274, 1849–1850.
2.
BrysbaertM.NazirT. (2005). Visual constraints in written word recognition: Evidence from the optimal viewing-position effect.Journal of Research in Reading28, 216–228.
3.
CassarM.TreimanR. (1997). The beginnings of orthographic knowledge: Children's knowledge of double letters in words.Journal of Educational Psychology89, 631–644.
4.
CastlesA.ColtheartM. (1993). Varieties in developmental dyslexia.Cognition47, 149–180.
5.
CastlesA.ColtheartM. (2004). Is there a causal link from phonological awareness to success in learning to read?.Cognition91, 77–111.
6.
CastlesA.NationK. (2006). How does orthographic learning happen?.AndrewsS.From inkmarks to ideas: Current issues in lexical processingHove, UK: Psychology Press.
7.
FacoettiA.CattaneoC.GalliR.LorussoM. L. (2004). Right focusing deficit in dyslexic children.Brain and Cognition56, 119–120.
8.
GraingerJ.JacobsA. M. (1993). Masked partial-word priming in visual word recognition: Effects of positional letter frequency.Journal of Experimental Psychology: Human Perception and Performance19, 951–964.
9.
GreenD. W.LiowS. J. R.TngS. K.ZielinkskiS. (1996). Are visual search procedures adapted to the nature of the script?.British Journal of Psychology87, 311–326.
10.
HammondE. J.GreenD. W. (1982). Detecting targets in letters and non-letter arrays.Canadian Journal of Psychology36, 67–82.
11.
HunterZ. R.BrysbaertM.KnechtS. (2007). A foveal word reading requires interhemisperic communication.Journal of Cognitive Neuroscience19, 1373–1387.
12.
KruegerL. E. (1970). Visual comparison in a redundant display.Cognitive Psychology7, 314–357.
13.
LibermanI. Y.ShankweilerD.FischerF. W.CarterB. (1974). Explicit syllable and phoneme segmentation in the young child.Journal of Experimental Child Psychology18, 201–212.
14.
LupkerS. J.PereaM.DavisC. J. (2008). Transposed-letter effects: Consonants, vowels and letter frequency.Language and Cognitive Processes23, 93–116.
15.
MasonM. (1975). Reading ability and letter search times: Effects of orthographic structure defined by single-letter positional frequency.Journal of Experimental Psychology: General104, 146–166.
16.
MasonM. (1982). Recognition time for letter and non-letters: Effects of serial position, array size and processing order.Journal of Experimental Psychology: Human Perception and Performance8, 724–738.
17.
MasonM.KatzL. (1976). Visual processing of non-linguistic strings: Redundancy effects and reading ability.Journal of Experimental Psychology: General105, 338–348.
18.
MayznerM. S.TresseltM. E. (1965). Tables of single-letter and digram frequency counts for various word-length and letter-position combinations.Psychonomic Monograph Supplements1, 13–30.
19.
McClellandJ. L.JohnsonJ. L. (1977). The role of familiar units in the perception of words and nonwords.Perception and Psychophysics22, 249–261.
20.
NelsonH. E. (1991). National Adult Reading Test (NART). (2). Windsor: The NFER-Nelson Publishing Company Ltd.
21.
NuerkH. C.ReyA.GrafR.JacobsA. M. (2000). Phonological sublexical units in visual word recognition.Current Psychology Letters: Behaviour, Brain & Cognition2, 25–36.
22.
PactonS.PerruchetP.FayolM.CleeremansA. (2001). Implicit learning in real world context: The case of orthographic regularities.Journal of Experimental Psychology: General130, 401–426.
23.
PitchfordN. J.LedgewayT.MastersonJ. (in press). Effects of orthographic processes on letter position encoding.Journal of Research in Reading.
24.
PitchfordN. J.MastersonJ.LedgewayT. (2004). Evidence for serial and global encoding of letter identity and position in a visual search task using skilled and dyslexic adult readers.Perception33, Suppl.150.
25.
RavenJ.RavenJ. C.CourtJ. H. (2000). Standard progressive matrices: 2000 editionOxford, UK: Oxford Psychologist Press.
26.
ReyA.ZieglerJ. C.JacobsA. M. (2000). Graphemes are perceptual reading units.Cognition75, B1–B12.
27.
RoachN. W.HogbenJ. H. (2007). Impaired filtering of behaviourally irrelevant visual information in dyslexia.Brain130, 771–785.
28.
ShillcockR. C.McDonaldS. A. (2005). Hemispheric division of labour in reading.Journal of Research in Reading28, 244–257.
29.
TydgatI.GraingerJ. (2007). Serial position effects in identification of letters, digits, and symbols: New evidence from the Reicher–Wheeler task. Manuscript submitted for publication.
30.
VellutinoF. R.ScanlonD. M.TanzmanM. S. (1994). Components of reading ability: Issues and problems in operationalizing word identification, phonological coding and orthographic coding.LyonG. R.Frames of reference for the assessment of learning disabilities: New views on measurement issuesBaltimore, MD: Brookes.
31.
WhitneyC. (2001). How the brain encodes the order of letters in a printed word: The SERIOL model and selective literature review.Psychonomic Bulletin & Review8, 221–243.
32.
WhitneyC. (in press). Supporting the serial in the SERIOL model.Language and Cognitive Processes.
33.
WhitneyC.BerndtR. S. (1999). A new model of letter string encoding: Simulating right neglect dyslexia.Progress in Brain Research121, 143–163.
34.
WhitneyC.CornelissenP. (2005). Letter-position encoding and dyslexia.Journal of Research in Reading28, 274–301.
