Do you see a link between text (1) and text (2). Text(1) : if interventions on upper-level variables are impossible, given the levels assumption, it does not make sense to investigate the conditions under which the causal relations and the results of interventions on micro-level variables can be coherently mapped into interventions involving macro-models. If exclusionism is correct, there are no genuine macro-interventions to relate to micro-interventions and upper -level variables are always causally inert.
Text (2): Anyone who has ever had the experience of holding back laughter in a serious or solemn context. In such situations, it seems that the conscious will is able to control and inhibit an automatic and spontaneous reaction - laughter - which would have been triggered by the situation if we had let it express itself. In other words, the causal efficacy of voluntary inhibition appears in a counterfactual way: if the subject hadn't held back, then he would have laughed out loud. This counterfactual expresses the actual causal efficacy of voluntary control on the non-initiation of laughter. This raises the question of the link between the automatic processes that underlie laughter and the intentional control that represses it. How do these two types of process interact to produce observable behavior? Can we propose a formal model to account for this interaction ?
Suppose that by comparing the neurophysiological state of subjects just before they burst out laughing, we have identified a set of biological properties F_1,...,F_n positively correlated with the onset of laughter. These properties can be either binary (i.e. present or absent), or gradable (i.e. able to take on different values on a continuous scale, ex. the concentration level of a certain neurotransmitter). These properties are assumed to be mutually compatible (they can be instantiated simultaneously in the same subject) and independent. 
For any gradable property F_i, it is assumed that there is an optimal value o_i such that the probability of the subject laughing at the next instant is maximal when F_i=o_i, all other things being equal.   If F_i is a binary property, o_i=1, since instantiating F_i increases the probability of laughter by hypothesis.
We assume that the act of refraining from laughing is all the more difficult the closer the F_i properties are to their optimal o_i values. Now, let's suppose that at a given instant, a subject instantiates a configuration of F_i properties that is very favorably associated with laughter, but at the same instant, he intends not to laugh. Thus, if the strength with which the subject inhibits his laughter is quantified by a variable I taking its values between 0 and 1 (I=0 corresponding to an absence of inhibition and I=1 to maximum inhibition), we can assume that the value of I depends on the social context: it will be close to 1 in a serious context and close to 0 in a relaxed one.
For the sake of model simplicity, we assume that the actual onset of laughter depends on the value of a binary variable R (if R=1 the subject laughs, 0 otherwise). It is assumed that voluntary inhibition I has a negative influence on R, while physiological properties F_i have a positive influence on R, the closer they are to their optimal values o_i.
Scope of the model. This model makes it possible to account for variable aspects of the determination and inhibition of laughter:
- The different factors likely to trigger laughter (humorous stimuli, tickling, laughing gas, etc.) can correspond to different F_i properties with different weights of influence on R. 
- The further the F_i properties are from their optimal o_i values, the less inclined to laugh and the easier it is to inhibit.
- Borderline cases correspond to situations where positive stimulation (the combination of properties F_i) and voluntary inhibition (I) have approximately equal and opposite strengths.  In other words, laughter is about to be triggered because positive stimulation slightly outweighs inhibition, or conversely, laughter is just about to be inhibited because voluntary inhibition slightly outweighs positive stimulation.
Limits. The model takes F_1,...,F_n as the essential realizers of laughter, strictly separating them from I, the voluntary control variable, in that the two intervene in a parallel way on R. However, it is possible for the properties F_i and the variable I to interact directly.For example, certain laughter triggers such as laughing gas could affect not only F_i but also I, or I could act on F_i rather than just R. Moreover, although the term "voluntary control" is psychological in nature, there is nothing to prevent it from being entirely reducible to lower-level properties.