Behavioral Science Institute Dynamical Systems Group

1. Behavioral Science Institute Dynamical Systems Group Planning in ActionDynamical Modeling of Developing Decision-making ProcessesRalf Cox & Ad Smitsman

2. Behavioral Science Institute Planning in Action Program • Hand use (limb selection): Basic results & Mechanisms • Planning (of hand use) • Perseveration experiment - Adults • Model • Perseveration experiment - Young children • Conclusions and Prospects

3. LH RH • 1 inch3 cubes presented in randomized order in nine positions • left-handed and right-handed adults Behavioral Science Institute Planning in Action Hand Use in Adults - Borrowed Setup by Gabbard, Misaki & Rabb, 1997; Gabbard & Rabb, 2000, 2004

4. Behavioral Science Institute Planning in Action Mechanisms of Hand Use - Borrowed Two mechanisms (working next to each other): • Motor dominance  manifested in handedness • Attentional information  spatial or task-related • Motor dominance is controlling factor in programming hand use at midline and ipsilateral hemispace. • Attentional information alters the programming of the movement in contraleteral hemispace.  Cannot really explain the frequency distributions.  As yet no model combines these two mechanisms.

5. Behavioral Science Institute Planning in Action About Making Choices… Planning is a decision-making process for actions to take (or inferences to make) with a number of defining properties. It is: • a dynamical process… • a multi-causal process… • an embodied process… • an embedded process… But also: • subjected to preferences • working on several time-scales (history)

6. 90o(1) 90o(2) 30o 30o 10o 10o Right-handed participant Training on non-preferred hand Behavioral Science Institute Planning in Action The experiment we performed is as follows • Adult participants: 14 righthanders and 10 lefthanders • Three training conditions: • Random (Gabbard) • Non-preferred hand (test 1) • Preferred hand (test 2) • Test: 4 training (T) trials followed by 2 ‘neutral’ (N) trials • T-trials are on (-)10o and (-)30o • N-trials are on (-)90o

7. Lefthanders (N=8) Righthanders (N=10) use of preferred hand Behavioral Science Institute Planning in Action Hand-use Perseveration – Results (preliminary) • In the Random condition we replicated Gabbard et al.’s results. • In the two Test conditions:

8. Behavioral Science Institute Planning in Action Dynamical Model for Hand Use Lateral activation functionu(t) for each hand (site): • Obeying a continuous dynamics • Inhibitory coupling between the sites • Neurobiological noise • Motor dominance: Direction and strength as difference in resting levels between the sites.  Larger and opposite in righthanders compared to lefthanders. • Attentional information: Asymmetrical input to the sites.

9. lefthanders lefthanders righthanders righthanders 10 30 50 70 90 -70 -50 -30 -10 10 30 50 70 90 -70 -50 -30 -10 90(1) 90(2) R 90(1) 90(2) 90(1) 90(2) R 90(1) 90(2) Gabbard 98 98 98 93 75 30 13 7 8 20 19 25 42 95 99 99 100 100 experiment 25 25 63 100 100 50 70 90 100 100 model 99 100 98 93 76 22 13 6 6 24 23 26 37 90 99 100 100 100 model 23 21 63 100 100 52 65 90 100 100 Behavioral Science Institute Planning in Action Simulations of Hand-use Perseveration With this model we can reproduce (simulate) the frequency distributions of adult hand use in the Gabbard experiment. • A second (internal) input source is added to the sites:  Build up of a memory trace during the training trials.

10. Behavioral Science Institute Planning in Action Planning in Young Children’s Tool Use • Tool use involves decision making for action on several levels and time-scales. • Earlier decisions prepare later ones. • Decision-making process is continuous and under constant influence of: • various perceptual input • (motor) preferences • training or memory of earlier actions Experiment & Model: Effect of training and hand preference on the decision which hand to use for grasping a spoon.

11. Design: • H-p: Determining the hand-preference in 5 neutral (N) trials • T & C: 4 training (T) trialsfollowedby 2neutral trials Behavioral Science Institute Planning in Action Hand-use Perseveration - Experiment • Children of 14 (N=21), 24 (N=19) and 36 (N=26) months old • Three conditions: • Hand-preference condition • Test condition • Control condition

12. Preferred hand Non-preferred hand 36 mo 14 mo subgroup 24 mo Behavioral Science Institute Planning in Action Hand-use Perseveration - Results • 24 & 36 mo: significant perseveration • 14 mo: not significant • subgroup: significant perseveration

13. 24 mo – perseveration 14 mo – much variability 36 mo – no perseveration Behavioral Science Institute Planning in Action Simulations • Resting-level difference is age dependent:  Largest in 36 mo and smallest in 14 mo. Examples:

14. Behavioral Science Institute Planning in Action Conclusions The model realistically: • combines perceptual input, motor preference and memory • simulates behavior as task and context dependent • reproduces individual and group differences Future work on the model: • Simulate timing effects in the task. • Adjustment of hand choice (switch) during the task, due to changes in the perceptual-motor workspace (earlier studies). Hand use: • The decision which hand to use is affected by previous decisions. • This decision is mediated by the strength of the preference.