While known reinforcers of behavior are outcomes that are valuable to the organism, recent research has demonstrated that the mere occurrence of an own-response effect can also reinforce responding. In this paper we begin investigating whether these two types of reinforcement occur via the same mechanism. To this end, we modified two different tasks, previously established to capture the influence of a response's effectiveness on the speed of motor-responses (indexed here by participants' reaction times). Specifically, in six experiments we manipulated both a response's 'pure' effectiveness and its outcome value (e.g., substantial versus negligible monetary reward) and measured the influence of both on the speed of responding. The findings strongly suggest that post action selection, responding is influenced only by pure effectiveness, as assessed by the motor system; thus, at these stages responding is not sensitive to abstract representations of the value of a response (e.g., monetary value). We discuss the benefit of distinguishing between these two necessary aspects of adaptive behavior namely, fine-tuning of motor-control and striving for desired outcomes. Finally, we embed the findings in the recently proposed Control-based response selection (CBRS) framework and elaborate on its potential for understanding motor-learning processes in developing infants. By definition, human behavior is strengthened by reinforcers 1,2 : Valued outcomes increase the vigor and frequency of actions that have produced them. As those reinforcing indices have been repeatedly linked to the value or worth of outcomes, it came as a surprise that substantial body of recent research found that responses can also be reinforced by neutral outcomes. Specifically, the mere fact that a response leads to a mundane perceptual change in the environment has been repeatedly demonstrated to be enough to increase the speed and to some degree, the frequency of that response 3-7. These findings could be taken as evidence that action-effectiveness generates value and hence, by making the previously neutral perceptual effect valuable, influences responding through the same mechanism as established reinforcers-such as monetary rewards-do. Yet, some empirical evidence as well as theory suggests that action effectiveness and 'classic' reinforcers operate through somewhat different routes. In the present paper, we test whether monetary rewards as classic reinforcers motivate behavior in the same way as action effectiveness does.

An important model for explaining humans’ feeling of agency—the Comparator model—draws on ideas used to explain effective motor control. The model describes how our brain estimates the degree of control over the environment offered by a specific motor program (in short, an action’s effectiveness). However, given its current level of specification, the model is at best vague on how (or even whether) the prediction of effectiveness of an action is dynamically updated. To test the issue empirically, our participants performed multiple experimental blocks of a task (reliably shown to measure reinforcement from effectiveness) in which blocks with and without action-effects (or with spatially unpredictable feedback) were interlaced. This design creates a sinusoidal-like objective increase or decrease in effectiveness (quantified as the n-trials back probability of receiving feedback), which participants were unable to report. As previously found, response speed indexed reinforcement from effectiveness. The results suggest that reinforcement from effectiveness is sensitive to both the degree and trend of effectiveness; that is, reinforcement is sensitive to whether it is increasing, decreasing, or is unchanged. Given the previous links made between reinforcement from effectiveness and the computation of effectiveness by the motor-system, the results are the first to show an online, dynamic and complex sensitivity to a motor-programs’ effectiveness that is directly translated to its production. The importance of testing the so-called sense of agency in a dynamic environment and the implications of the current findings for a dominant model of the sense of agency are discussed.

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