Which executive functions predict verbal/visuospatial working memory and fluid intelligence when controlling for processing speed ?

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Poster

Reference

GOLAY, Philippe, LECERF, Thierry

GOLAY, Philippe, LECERF, Thierry. Which executive functions predict verbal/visuospatial working memory and fluid intelligence when controlling for processing speed ? In: 13th Congress of the Swiss Psychological Society, Basel, 11-12 september 2013, 2013

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http://archive-ouverte.unige.ch/unige:29602

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INTRODUCTION

CONCLUSION RESULTS

Contact: [email protected]

SSP²⁰¹³ - 13^TH CONGRESS OF THE SWISS PSYCHOLOGICAL SOCIETY, UNIVERSITY OF BASEL, 11-12.9.2013

Which executive functions predict verbal/visuospatial working memory and fluid intelligence when controlling for processing speed?

Philippe Golay

^1,2

& Thierry Lecerf

^1,2

1Faculty of Psychology and Educational Sciences, University of Geneva, ²Distance Learning University, Switzerland

• Executive functions have been shown to play a key role in working memory and fluid intelligence performance.

• Although working memory capacity is frequently considered as a unitary construct, some studies have shown that verbal and visuospatial working memory tasks load on two different factors.

• It is often hypothesized that visuospatial working memory tasks places stronger demands on executive functioning than the verbal tasks.

• The relationships between executive functions, working memory and fluid intelligence has been rarely investigated while taking into account the

verbal-visuospatial distinction.

• Beside executive functions, processing speed could also account for large parts of variance in working memory and fluid intelligence performance and should be statistically controlled for.

GOALS OF THE PRESENT STUDY

• The first goal of this study was to assess whether verbal and visuospatial working memory and processing speed accounted for separate parts of variance in fluid intelligence performance.

• The second goal was to investigate the specific contribution of three executive functions (shifting, updating, inhibition) to fluid intelligence and to verbal/visuospatial working memory tasks, after taking processing speed into account.

METHOD

• Results indicated that both working memory and processing speed accounted for unique variance in fluid intelligence tasks.

• Only visuospatial but not verbal working memory predicted variation in fluid intelligence.

• To deal with these goals, we used a latent variable approach via structural equation modeling.

• A total of 17 tasks measuring processing speed, shifting, updating,

inhibition, fluid intelligence, verbal and visuospatial working memory were administered to 158 young adults aged between 18 and 31 years.

• The 17 tasks were administered in the same order in 2 sessions spaced by 7 days.

Fluid Intelligence Working

Memory (unitary)

Processing Speed

Fluid Intelligence Visuospatial

Working Memory

Verbal Working

Memory

.109

R2000 u

D2000 u

u Number

Letter

u Local

Global

u Plus

Minus

Shifting

u Letter

Updating

u Cube

Updating

u Keep

Track

Updating

u Stroop

u Stop

Signal

u Arrow

Task

Inhibition

Matrix u

Task

Direction u

Span Task

Visuospatial Working

Memory

Reading u

Span

Operation u

Span

Memory

u

u Coding

u Symbol

Search

Fluid Intelligence Processing u

Speed

.511*

.591*

.299

Shifting

Updating

Inhibition

Memory

u

Fluid Intelligence

u

-.163 .046

.018

Tasks

Constructs 1^st session 2^nd session Shifting 1. Plus Minus

10. Number Letter 2. Local Global

Updating 3. Keep Track 11. Letter Updating 12. Cube Updating

Inhibition 4. Arrow Task

13. Stop Signal 5. Stroop

Processing Speed 6. Symbol Search 14. Coding Fluid Intelligence 7. R2000 15. D2000 Verbal

Working Memory 8. Reading Span 16. Operation Span

Visuospatial

Working Memory 9. Matrix Task 17. Direction Span Task

Participants N Age % Female % Right handed

158 Mean = 21.34 (SD = 2.17) 88.0 88.6

min 18, max 31 (139/158) (140/158)

• Results indicated that the three executive functions and processing speed were differentially related to fluid intelligence and working memory:

• When controlling for processing speed, fluid intelligence was only predicted by updating.

• Working memory performance (both verbal & visuospatial) was also only predicted by updating when processing speed was taken into account.

• Finally and most revealing, the near-zero residual correlations between working memory and fluid intelligence suggested that the commonality between these construct could be solely explained by the contribution of executive functioning and processing speed.

• χ² = 9.777 , df = 9, p = 0.369

• SRMR = 0.040, RMSEA = 0.023

• Working memory is better represented by two factors (Wald chi-square test of parameter equalities : 29.544, df = 1, p = 0.000)

• Both verbal and visuospatial working memory shared a large amount of variance with fluid intelligence

Shifting

Updating

Inhibition

Memory

Verbal Working Memory

Fluid Intelligence Processing

Speed

• 1^st objective: do verbal and visuospatial working memory and processing speed account for separate parts of variance in fluid intelligence performance ?

• χ² = 165.142, df = 102, p = 0.000

• SRMR = 0.066 , RMSEA = 0.063

• Loadings between executive

functions and working memory were not statistically different between verbal or visuospatial domains (all Wald chi-square test of parameter equalities p > 0.05)

• R² Fluid Intelligence = 0.561

• R²Visuospatial WM = 0.560

• R²Verbal WM = 0.468

R2000 u

D2000 u

Matrix u

Task

DST u

Memory

Reading u

Span

Operation u

Span

Memory Fluid Intelligence

.422*

.526*

.559*

• Preliminary analysis: distinction between verbal and visuospatial components of working memory

• 2^nd objective: what is the specific contribution of the three executive functions (shifting, updating, inhibition) to fluid intelligence and to verbal/visuospatial working memory performance when controlling for processing speed) ?

• Working memory and processing speed accounted for unique variance in fluid intelligence performance. Only visuospatial but not verbal working memory predicted variation in fluid intelligence.

• When controlling for processing speed, only updating predicted working

memory and fluid intelligence performance. Although distinct, visuospatial and verbal working memory did not appeared to be differentially related to executive functioning with young adults.

• In addition, results suggested that the common variance between working memory and fluid intelligence could solely be explained by a mixture of updating and processing speed.

• Stroop, Arrow task: only correct trials longer than 200ms and shorter than 2000 ms were analyzed.

• Local Global, Number Letter: only correct trials longer than 400ms and shorter than 4000ms were analyzed.

• Because Structural Equation Modeling is sensible to extreme values, all

data were screened and trimmed for outliers (data farther than ± 3 SD from the mean were replaced by a value that was 3 SD from the mean).

• No more than 0.56% of the total of observations were affected by this

trimming procedure (no more than 2.56% of the observations of any task).

• All models were estimated with a Maximum Likelihood procedure using the Mplus statistical package (version 6.11).