Kim Uittenhove

The time course of strategy sequential difficulty effects: an ERP study in arithmetic

Uittenhove and Lemaire (Exp Psychol 59(5):295–301, 2012) found that we are slower when executing a strategy following a difficult strategy than when executing the same strategy following an easier strategy (i.e., strategy sequential difficulty effects). Uittenhove and Lemaire suggested that difficult strategies temporarily reduce available executive capacities, interfering with the next strategy execution. In this study, we used ERP to determine the time course of these effects. In a computational estimation task, we found greater cerebral activities during strategy execution following a more difficult compared to an easier strategy. Interestingly, greater cerebral activities were most apparent immediately after the encoding of the problem and not during encoding or in later stages of processing. This suggests that strategy sequential difficulty effects interfere most with the retrieval of procedures in contrast to execution of these procedures. We discuss implications of these findings for further understanding of execution of cognitive strategies.

Strategy sequential difficulty effects in Alzheimer patients: A study in arithmetic

Objective: Consistent with Uittenhove and Lemaire (2012), we expected that strategy execution would be slower following execution of a difficult strategy than after an easy strategy (strategy sequential difficulty, SSD, effects). Moreover, we expected larger SSD effects in older adults than in young adults, and especially in Alzheimers disease (AD) patients, a population with marked cognitive impairments. Method: A total of 25 young and older (41 AD and 25 healthy) adults were asked to execute rounding strategies to solve arithmetic problems (e.g., solving 43 + 68 by rounding operands down or up, e.g., 40 + 70 = 110). We measured solution latencies and percentage errors with a strategy as a function of the difficulty of the just-executed strategy. Results: Solution latencies were significantly shorter following the easier rounding-down strategy than following the harder rounding-up strategy, F(2, 156) = 35.8. Moreover, this effect was significantly larger in AD patients, F(1, 78) = 117.4. Conclusions: We found comparable SSD effects in young and healthy older adults but dramatically increased SSD effects in AD patients. This has implications to further our understanding of strategic aspects underlying decreased cognitive functioning in AD patients.

Ten-year-old children strategies in mental addition: A counting model account.

For more than 30 years, it has been admitted that individuals from the age of 10 mainly retrieve the answer of simple additions from long-term memory, at least when the sum does not exceed 10. Nevertheless, recent studies challenge this assumption and suggest that expert adults use fast, compacted and unconscious procedures in order to solve very simple problems such as 3+2. If this is true, automated procedures should be rooted in earlier strategies and therefore observable in their non-compacted form in children. Thus, contrary to the dominant theoretical position, childrens behaviors should not reflect retrieval. This is precisely what we observed in analyzing the responses times of a sample of 42 10-year-old children who solved additions with operands from 1 to 9. Our results converge towards the conclusion that 10-year-old children still use counting procedures in order to solve non-tie problems involving operands from 2 to 4. Moreover, these counting procedures are revealed whatever the expertise of children, who differ only in their speed of execution. Therefore and contrary to the dominant position in the literature according to which childrens strategies evolve from counting to retrieval, the key change in development of mental addition solving appears to be a shift from slow to quick counting procedures.

Fast automated counting procedures in addition problem solving: When are they used and why are they mistaken for retrieval?

Contrary to a widespread assumption, a recent study suggested that adults do not solve very small additions by directly retrieving their answer from memory, but rely instead on highly automated and fast counting procedures (Barrouillet & Thevenot, 2013). The aim of the present study was to test the hypothesis that these automated compiled procedures are restricted to small quantities that do not exceed the size of the focus of attention (i.e., 4 elements). For this purpose, we analyzed the response times of ninety adult participants when solving the 81 additions with operands from 1 to 9. Even when focusing on small problems (i.e. with sums ⩽10) reported by participants as being solved by direct retrieval, chronometric analyses revealed a strong size effect. Response times increased linearly with the magnitude of the operands testifying for the involvement of a sequential multistep procedure. However, this size effect was restricted to the problems involving operands from 1 to 4, whereas the pattern of response times for other small problems was compatible with a retrieval hypothesis. These findings suggest that very fast responses routinely interpreted as reflecting direct retrieval of the answer from memory actually subsume compiled automated procedures that are faster than retrieval and deliver their answer while the subject remains unaware of their process, mistaking them for direct retrieval from long-term memory.

Sequential difficulty effects during execution of memory strategies in young and older adults

This study aimed at uncovering factors influencing execution of memory strategies and at furthering our understanding of ageing effects on memory performance. To achieve this end, we investigated strategy sequential difficulty (SSD) effects recently demonstrated by Uittenhove and Lemaire in the domain of problem solving. We found that both young and older participants correctly recalled more words using a sentence-construction strategy when this strategy followed an easier strategy (i.e., repetition strategy) or a harder strategy (i.e., mental-image strategy). These SSD effects were of equal magnitude in young and older adults, correlated significantly with Stroop performance in both young and older adults and correlated with N-back performance only in young adults. These findings have important implications for furthering our understanding of memory strategy execution and age-related variations in memory performance, as well for understanding mechanisms underlying SSD effects.

Strategy difficulty effects in young and older adults' episodic memory are modulated by inter-stimulus intervals and executive control processes☆

Efficient execution of strategies is crucial to memory performance and to age-related differences in this performance. Relative strategy complexity influences memory performance and aging effects on memory. Here, we aimed to further our understanding of the effects of relative strategy complexity by looking at the role of cognitive control functions and the time-course of the effects of relative strategy complexity. Thus, we manipulated inter-stimulus intervals (ISI) and assessed executive functions. Results showed that (a) performance as a function of the relative strategy difficulty of the current and previous trial was modulated by ISI, (b) these effects were modulated by inhibition capacities, and (c) significant age differences were found in the way ISI modulates relative strategy difficulty. These findings have important implications for understanding the relationships between aging, executive control, and strategy execution in episodic memory.

On the sources of forgetting in working memory: The test of competing hypotheses:

Whether forgetting from working memory (WM) is only due to interference or is also caused by temporal decay is still a matter of debate. In the present study, this question was examined using complex span tasks in which each memory item was followed by a series of processing episodes, the duration and number of which were varied. It is known that recall performance in these tasks depends on the cognitive load (CL) of concurrent processing conceived as the ratio between processing time and free time, higher CL resulting in lower spans. The decay-and-refresh hypothesis accounts for this effect by assuming that memory traces decay during processing but are refreshed during free time. This hypothesis predicts lower recall performance with longer processing episodes, but no effect of their number as long as CL remains constant. The interference-only hypothesis supposes that free time is used to alleviate the interference created by processing distractors. This hypothesis is potentially compatible with an effect of the duration of processing episodes through increased interference, but predicts a detrimental effect of their number. In three experiments, the recall pattern fitted the predictions of the decay-and-refresh hypothesis for verbal WM, but that of the interference-only hypothesis for visuospatial WM. Although the entire pattern of data is more easily accommodated by the decay-and-refresh hypothesis than by its interference-only contender, our results suggest that it is unwise to aim at identifying a unique source to a complex phenomenon like WM forgetting.

Performance Control in Numerical Cognition

Abstract In this chapter, we review existing data on how performance control operates in numerical cognition. In particular, we discuss how this occurs via strategic variations and executive control. Moreover, we clarify the role of executive control in every dimension of strategy use, and we use this framework to explain the effects of life span development on performance control in numerical cognition. A large body of literature is reviewed, ranging from correlational to experimental studies. Most noteworthy, we illustrate how sequential effects inform us on the role of executive control in different strategy dimensions. Indeed, when selected and executed in isolation, strategies require executive resources. This requirement is much enlarged when strategies have to be executed in a sequential context, as they often are in experimental settings.