How does the brain combine information predictive of the value of a visually guided task (incentive value) with information predictive of where task-relevant stimuli may occur (spatial certainty)? Human behavioural evidence indicates that these two predictions may be combined additively to bias visual selection (Additive Hypothesis), whereas neuroeconomic studies posit that they may be multiplicatively combined (Expected Value Hypothesis). We sought to adjudicate between these two alternatives. Participants viewed two coloured placeholders that specified the potential value of correctly identifying an imminent letter target if it appeared in that placeholder. Then, prior to the target’s presentation, an endogenous spatial cue was presented indicating the target’s more likely location. Spatial cues were parametrically manipulated with regard to the information gained (in bits). Across two experiments, performance was better for targets appearing in high versus low value placeholders and better when targets appeared in validly cued locations. Interestingly, as shown with a Bayesian model selection approach, these effects did not interact, clearly supporting the Additive Hypothesis. Even when conditions were adjusted to increase the optimality of a multiplicative operation, support for it remained. These findings refute recent theories that expected value computations are the singular mechanism driving the deployment of endogenous spatial attention. Instead, incentive value and spatial certainty seem to act independently to influence visual selection.

大脑如何将预测视觉指导任务价值的信息（激励值）与预测可能发生任务相关刺激的信息（空间确定性）相结合？人类行为证据表明，这两个预测可能会相加组合以偏向视觉选择（附加假设），而神经经济学研究认为它们可能相乘相加（预期价值假设））。我们试图在这两种选择之间进行裁定。参与者查看了两个彩色占位符，它们指定了正确识别即将出现的字母目标（如果它出现在该占位符中）的潜在价值。然后，在呈现目标之前，先呈现一个内在的空间提示，指示目标更可能的位置。根据获得的信息（以位为单位）对空间提示进行了参数化处理。在两个实验中，出现在高价值占位符和低价值占位符上的目标的性能更好，而目标出现在有效提示位置的目标则表现更好。有趣的是，如贝叶斯模型选择方法所示，这些效果没有相互作用，显然支持了加性假设。即使调整条件以增加乘法运算的最优性，支持它仍然。这些发现驳斥了最近的理论，即期望值计算是驱动内源性空间注意力部署的单一机制。相反，激励价值和空间确定性似乎独立地影响视觉选择。