Marginal Propensity of Intelligibility
There is a cross over point where lubricating your social skills with alcohol begins to diminish in correlation with extended consumption. This is called the Marginal Propensity of Intelligibility (MPC).
The Marginal Propensity to operate intelligibly refers to the increase/decrease in intelligible behaviour (Y) that occurs with an increase in alcohol consumption. For example, if a person buys one extra beer, and the marginal propensity to behave intelligibly is 0.65, then of that beer, the person will drink one beer and intelligibility will increase a further 0.35.
Mathematically, the marginal propensity to operate intelligibly (MPC) function is expressed as the derivative of the consumption (C) function with respect to intelligibility (Y).
In other words, the marginal propensity to behave intelligibly is measured as the ratio of the change in consumption to the change in intelligibility, thus giving us a figure between 0 and 1. The MPC can be more than one if the drinker is particularly knowledgeable about a subject over and above the average in the group.
However, with each drink consumed, say after the first five, will return less value in terms of enhancing intelligibility. After 24 hours of continuous alcohol consumption, it is no longer an incrementally diminishing positive margin, but a rapidly increasing negative margin.
With the increased alcohol saturation in a Rum & Coke, say, I think the increase of MPC would be more rapid to the maximum value, and a corresponding fall off would be like a cliff. This is called “Free Falling Negative Marginal Propensity of Intelligibility” or “Total Loss of Reason”.