A B • C D Trained, no force field 1st trial under force field 500th trial under force field Unexpectedly without force field Figure 2. Centre-out reaching task. Dots indicate the centre and the eight targets.
In a hypothetical experiment, a monkey was trained over 500 trials to perform well in a centre-out reaching task. The trajectory of the trained animal’s hand from the start point in the centre to each of the eight peripheral targets was tracked and is plotted in Panel A of Figure 2 below.
Once the animal was trained in this task, a uniform force field was then applied to the manipulandum arm that the monkey had to move to reach the targets. The animal was trained under this new force field regimen for a further 500 trials. During one of the last trials, the force field was unexpectedly not applied. The movements in this ‘unexpected’ condition are shown in Panel D. ‘Trial’ refers to a complete set of eight movements, one to each of the targets.
• Use Panels B and C to illustrate: (i) the direction of the uniform force field that must have been used in the experiment; and (ii) the trajectories of the hand that you would expect on the first of the trials carried out under the force field regimen (B) and the 500th trial under the force field (C).
• Use appropriate terminology to describe the trajectories and your reasoning for their shapes and the inferred direction of the force field.
I have attached Figure 2. Centre-out reaching task. Dots indicate the centre and the eight targets.
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