Dror Dotan

Is the visual analyzer orthographic-specific? Reading words and numbers in letter position dyslexia

Letter position dyslexia (LPD) is a deficit in the encoding of letter position within words. It is characterized by errors of letter migration within words, such as reading trail as trial and form as from. In order to examine whether LPD is domain-specific, and to assess the domain-specificity of the visual analysis system, this study explored whether LPD extends to number reading, by testing whether individuals who have letter migrations in word reading also show migrations while reading numbers. The reading of words and numbers of 12 Hebrew-speaking individuals with developmental LPD was assessed. Experiment 1 tested reading aloud of words and numbers, and Experiment 2 tested same-different decisions in words and numbers. The findings indicated that whereas the participants with developmental LPD showed a large number of migration errors in reading words, 10 of them read numbers well, without migration errors, and not differently from the control participants. A closer inspection of the pattern of errors in words and numbers of two individuals who had migrations in both numbers and words showed qualitative differences in the characteristics of migration errors in the two types of stimuli. In word reading, migration errors appeared predominantly in middle letters, whereas the errors in numbers occurred mainly in final (rightmost) digits. Migrations in numbers occurred almost exclusively in adjacent digits, but in words migrations occurred both in adjacent and in nonadjacent letters. The results thus indicate that words can be selectively impaired, without a parallel impairment in numbers, and that even when numbers are also impaired they show different error pattern. Thus, the visual analyzer is actually an orthographic visual analyzer, a module that is domain-specific for the analysis of words.

Finger Tracking Reveals the Covert Stages of Mental Arithmetic

We introduce a novel method capable of dissecting the succession of processing stages underlying mental arithmetic, thus revealing how two numbers are transformed into a third. We asked adults to point to the result of single-digit additions and subtractions on a number line, while their finger trajectory was constantly monitored. We found that the two operands are processed serially: the finger first points toward the larger operand, then slowly veers toward the correct result. This slow deviation unfolds proportionally to the size of the smaller operand, in both additions and subtractions. We also observed a transient operator effect: a plus sign attracted the finger to the right and a minus sign to the left and a transient activation of the absolute value of the subtrahend. These findings support a model whereby addition and subtraction are computed by a stepwise displacement on the mental number line, starting with the larger number and incrementally adding or subtracting the smaller number.

Separate mechanisms for number reading and word reading: Evidence from selective impairments

Do number reading and word reading use the same cognitive mechanisms? We examined this question through the looking glass of dissociations between impairments in number and word reading. We report two women with selective deficits in number reading, who read words normally. An examination of their impairment pattern indicated that the specific locus of their number reading deficits is in processes that handle the numbers structure: both were impaired in parsing a digit string into triplets, and one of them was also impaired in generating the numbers verbal structure. In contrast to their structural deficits in number reading, their word reading was completely intact, including the structural processes in word reading (morphological analysis and assembly). We present this dissociation in the framework of a broader effort to examine dissociations between specific components in number and word reading. We went beyond general word-number dissociations: we used detailed cognitive models for word reading and for number reading, and analyzed them in order to identify which components of the number reading process are homologous to which components of words reading. We then show that even these homologous processes are dissociable: an examination of previously-reported dissociations, completed by the case studies presented here, indicated that each of the specific homologous sub-processes of word/number reading can be selectively impaired. We conclude that although the word and number reading pathways show much similarity, they are almost entirely separate.

On-line confidence monitoring during decision making

Humans can readily assess their degree of confidence in their decisions. Two models of confidence computation have been proposed: post hoc computation using post-decision variables and heuristics, versus online computation using continuous assessment of evidence throughout the decision-making process. Here, we arbitrate between these theories by continuously monitoring finger movements during a manual sequential decision-making task. Analysis of finger kinematics indicated that subjects kept separate online records of evidence and confidence: finger deviation continuously reflected the ongoing accumulation of evidence, whereas finger speed continuously reflected the momentary degree of confidence. Furthermore, end-of-trial finger speed predicted the post-decisional subjective confidence rating. These data indicate that confidence is computed on-line, throughout the decision process. Speed-confidence correlations were previously interpreted as a post-decision heuristics, whereby slow decisions decrease subjective confidence, but our results suggest an adaptive mechanism that involves the opposite causality: by slowing down when unconfident, participants gain time to improve their decisions.

Corrigendum to “On-line confidence monitoring during decision making” [Cognition 171 (2018) 112–121]

Corrigendum to “On-line confidence monitoring during decision making” [Cognition 171 (2018) 112–121] Dror Dotana,b,, Florent Meyniel, Stanislas Dehaene a Cognitive Neuroimaging Unit, CEA DRF/I2BM, INSERM, Université Paris-Sud, Université Paris-Saclay, F-91191 Gif/Yvette, France b Language and Brain Lab, School of Education and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel c Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France