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Fluid intelligence and the many faces of executive function

Fluid intelligence and the many faces of executive function . Helen Davis School of Psychology Murdoch University. Acknowledgements: Catherine Leong. Fluid intelligence. Raw reasoning ability Biological basis Closely aligned with g Increases until early adulthood

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Fluid intelligence and the many faces of executive function

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  1. Fluid intelligence and the many faces of executive function Helen Davis School of Psychology Murdoch University Acknowledgements: Catherine Leong

  2. Fluid intelligence • Raw reasoning ability • Biological basis • Closely aligned with g • Increases until early adulthood • Is there a simple, information-processing explanation for differences in fluid intelligence?

  3. Executive Function • Active selection of behaviour from alternatives • Strategy generation • Inhibition • Attention switching, goal maintenance, working memory • Monitoring & modifying performance (Rabbitt, 1997) • Frontal lobe related • Relation to fluid intelligence • Development (Bjorklund & Harnishfeger, 1989; Davis & Anderson, 2001) • Is EF general or task-specific?

  4. The Stroop Colour-Word Task • Conditions • Congruent: RED BLUEGREEN • Neutral: XXX XXXXXXX • Incongruent: BLUE GREENRED • Selectively attend to ink colour (not word) • Interference effect = incongruent – neutral • Facilitation effect = neutral - congruent

  5. Blocked trials GREEN RED BLUE ------------------------ XXX XXXX XXX ------------------------ GREEN RED BLUE Mixed trials XXXX GREEN BLUE ------------------------ XXX RED BLUE ------------------------ XXX GREEN RED The Stroop Colour-Word Task

  6. An accidental finding… • Blocked trials: • Interference effect decreases with age (7-10 years) • Facilitation effect - no change • Mixed trials: • Interference effect no change • Facilitation effect decreases with age (7-10 years) • Lack of interference / facilitation correlation

  7. Some enlightenment from Kane & Engle (2003)? • Working memory (WM) capacity and Stroop task (adults) • Blocked trials: • Interference effect (time cost) greater for low WM • Selective attention only? • Mixed trials: • No interference (time cost) difference between WM groups • Greater facilitation effect (time benefit) • Selective attention + goal maintenance?

  8. Research Questions • Does Stroop facilitation reflect goal neglect? • Is Stroop facilitation related to goal neglect on separate task? • Is Stroop facilitation related to working memory capacity? • Is Stroop facilitation distinct from Stroop interference? • Which, if any, of these executive function measures predict developmental change in fluid intelligence?

  9. Method Participants: • 7-year-olds (n = 34) • mean age = 7.4 (6.9 - 7.9) • 18 boys, 16 girls • 10-year-olds (n = 40) • mean age = 10.2 (9.7-10.9) • 26 boys, 14 girls

  10. Tasks • Raven’s Standard Progressive Matrices • Group test (fluid intelligence – raw score) • Digit span • forward (short-term memory) • backward (working memory)

  11. Stroop task • Individual, computer administered • 3 colour (red, green, blue) • Conguent, Incongruent, Neutral • 3 blocks of 36 mixed trials • Measured reaction time (RT) • Switching task • Computer administered(goal maintenance/neglect)

  12. Switching Task Stimuli

  13. Red taskPlant or animal?‘Z’ for plant ‘/’ for animal64 trials Green TaskSmall or large?‘Z’ for small ‘/’ for large64 trials Switching Task Procedure Dual TaskAlternating 4 trials red, 4 trials green64 trials total

  14. Results Raven’s Progressive Matrices

  15. Stroop Task Reaction Time • Facilitation effectF(1,68) = 52.62*** • Interference effectF(1,68) = 165.72*** • Facilitation x AgeF(1,68) = 3.03, p=.08 • Interference x AgeF(1,68) = 7.19** • AgeF(1,68) = 19.02***

  16. Digit Span • Age • ForwardF(1,68) = 13.58*** • Backward F(1,68) = 28.54***

  17. Switching Task • Switch costF(1,66) = 219.28*** • Switch cost x AgeF(1,66) = 6.95** • AgeF(1,66) = 40.50***

  18. Task Intercorrelations p < .05; p < .07; n.s.

  19. Stepwise Linear Regression – Predicting Fluid Intelligence from Executive Function

  20. In answer to research questions… • Does Stroop facilitation reflect goal neglect? • Is Stroop facilitation significantly related to goal neglect on separate task? NO • Is Stroop facilitation significantly related to working memory capacity? NO • Is Stroop facilitation distinct from Stroop interference? YES

  21. Which, if any, of these executive function measures predict: • Developmental change in fluid intelligence • Working memory (BDS) • Goal neglect (switch cost) • Selective attention (interference effect) • Whatever the facilitation effect is(!)

  22. Conclusions • The Stroop facilitation effect cannot be easily interpreted as an measure of goal neglect. • Executive functions are multiple. • The development of fluid intelligence may be the result of the summation of different executive functions maturing relatively independently.

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