Maaike Loncke

Order or disorder? Impaired Hebb learning in dyslexia.

The present study offers an integrative account proposing that dyslexia and its various associated cognitive impairments reflect an underlying deficit in the long-term learning of serial-order information, here operationalized as Hebb repetition learning. In nondyslexic individuals, improved immediate serial recall is typically observed when one particular sequence of items is repeated across an experimental session, a phenomenon known as the Hebb repetition effect. Starting from the critical observation that individuals with dyslexia seem to be selectively impaired in cognitive tasks that involve processing of serial order, the present study is the first to test and confirm the hypothesis that the Hebb repetition effect is affected in dyslexia, even for nonverbal modalities. We present a theoretical framework in which the Hebb repetition effect is assumed to be a laboratory analogue of naturalistic word learning, on the basis of which we argue that dyslexia is characterized by an impairment of serial-order learning that affects language learning and processing.

Executive control is shared between sentence processing and digit maintenance: evidence from a strictly timed dual-task paradigm

We investigated whether the comprehension of syntactically difficult sentences taxes the executive control component of working memory more than the comprehension of their easier counterparts. To that end, we tested the effect of sharing executive control between sentence comprehension and the maintenance of a digit load in two dual-task experiments with strictly controlled timing (Barrouillet, Bernardin, & Camos, 2004). Recall was worse after participants had processed one (Experiment 2) or two (Experiment 1) difficult sentences than after they had processed one or two easy sentences, respectively. This finding suggests that sentence processing and the maintenance of a digit load share executive control. Processing syntactically difficult sentences seems to occupy executive control for a longer time than processing their easy counterparts, thereby blocking refreshments of the memory traces of the digits so that these traces decay more and recall is worse. There was no effect of the size of the digit load on sentence-processing performance (Experiment 2), suggesting that sentence processing completely occupied executive control until processing was complete.

Coordinating the cognitive processes of writing : the role of the monitor

Moment to moment, a writer faces a host of potential problems. How does the writer’s mind coordinate this problem solving? In the original Hayes and Flower model, the authors posited a distinct process to manage this coordinating—that is, the “monitor.” The monitor became responsible for executive function in writing. In two experiments, the current authors investigated monitor function by examining the coordination of two common writing tasks—editing (i.e., correcting an error) and sentence composing—in the presence or absence of an error and with a low or high memory load for the writer. In the first experiment, participants could approach the editing and composing task in either order. On most trials (88%), they finished the sentence first, and less frequently (12%), they corrected the error first. The error-first approach occurred significantly more often under the low-load condition than the high-load condition. For the second experiment, participants were asked to adopt the less-used, error-first approach. Success in completing the assigned task order was affected by both memory load and error type. These results suggest that the monitor depends on the relative availability of working memory resources and coordinates subtasks to mitigate direct competition over those resources.

Who is dominating the Dutch neighbourhood? On the role of subsyllabic units in Dutch nonword reading

To assess the role of the subsyllabic units onset–nucleus (ON; spa rk) and rime (sp ark ) in Dutch visual word recognition, we compared lexical decisions to four groups of nonwords in which the existence of ONs and rimes was orthogonally manipulated. Nonwords with existent ONs and/or rimes were rejected more slowly and less accurately. ON and rime neighbours thus influence Dutch nonword reading to the same extent. Simulations with the interactive activation model (McClelland & Rumelhart, 1981) revealed that this model with left-to-right coded representations could not replicate the effects found in the lexical decision data whereas an adapted version with representations of onset, nucleus, and coda could. Effects of the larger units ON and rime emerged from activation patterns created by the smaller units onset, nucleus, and coda.

The role of executive control in resolving grammatical number conflict in sentence comprehension

In sentences with a complex subject noun phrase, like “The key to the cabinets is lost”, the grammatical number of the head noun (key) may be the same or different from that of the modifier noun phrase (cabinets). When the number is the same, comprehension is usually easier than when it is different. Grammatical number computation may occur while processing the modifier noun (integration phase) or while processing the verb (checking phase). We investigated at which phase number conflict and plausibility of the modifier noun as subject for the verb affect processing, and we imposed a gaze-contingent tone discrimination task in either phase to test whether number computation involves executive control. At both phases, gaze durations were longer when a concurrent tone task was present. Additionally, at the integration phase, gaze durations were longer under number conflict, and this effect was enhanced by the presence of a tone task, whereas no effects of plausibility of the modifier were observed. The finding that the effect of number match was larger under load shows that computation of the grammatical number of the complex noun phrase requires executive control in the integration phase, but not in the checking phase.