Table 2. Defined variables.
In any given trial, qA and qB were, respectively, the quantities of juice A and juice B offered to the animal, ρ was the relative value of the two juices, and ξ was the action cost. Parameters ρ and ξ were obtained from the logistic regression (Equation 1). The variable spatial congruence was set = 1 ( = 0) if the offer and the saccade target associated with a given juice (same color) were presented in the same (opposite) hemifield. Variables chosen offer loc only and chosen target loc only provided the best explanation (highest R2) only if it provided the sole explanation (see Materials and methods).
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Collapsed variable | Variable | Definition | Reference frame |
|---|---|---|---|---|
| 1 | Offer value (juice) | Offer value A | ρ qA + ξ δjuice A,+ | Juice |
| 2 | Offer value B | qB + ξ δjuice B,+ | Juice | |
| 3 | Chosen juice | 1 if juice B is chosen, 0 if juice A is chosen | Juice | |
| 4 | Offer value (cost) | Offer value − | Offer value A if A is high cost, offer value B if B is high cost | Cost |
| 5 | Offer value + | Offer value A if A is low cost, offer value B if B is low cost | Cost | |
| 6 | Chosen cost | 1 if low-cost offer is chosen, 0 if high-cost offer is chosen | Cost | |
| 7 | Offer value (location) | Offer value L | Value of the juice offered on the left | Visual |
| 8 | Offer value R | Value of the juice offered on the right | Visual | |
| 9 | Offer value (target) | Offer value target L | Value of the juice associated with target in the left hemifield | Action |
| 10 | Offer value target R | Value of the juice associated with target in the right hemifield | Action | |
| 11 | Cost of A | 1 if offer A is low cost, 0 if offer A is high cost | ||
| 12 | Offer A location | 1 if juice A is offered on left, 0 if juice A is offered on right | ||
| 13 | Target A location | 1 if target A is in left hemifield, 0 if target A is in right hemifield | ||
| 14 | Offer+ location | 1 if low-cost offer is on the left, 0 if low cost offer is on the right | ||
| 15 | Target+ location | 1 if low-cost target is in the left hemifield, 0 otherwise | ||
| 16 | Spatial congruence | 1 if offers and targets are spatially congruent, 0 otherwise | ||
| 17 | Chosen value | Offer value A if juice A chosen, offer value B if juice B chosen | ||
| 18 | Value ratio | Other/chosen value | ||
| 19 | Cost/benefit conflict | Cost of A × sign(offer value A – offer value B). 1 if there is conflict, 0 otherwise | ||
| 20 | Chosen offer loc only | 1 if the chosen offer is on the left, 0 otherwise | Visual | |
| 21 | Chosen target loc only | 1 if the chosen target is in the left hemifield, 0 otherwise | Action |