Where does stimulus collide?

In physiology a stimulus is any change in energy, whether mechanical, chemical, thermal, or electrical, that acts on excitable tissue and, once it crosses a threshold, evokes a response such as a nerve impulse or a muscle contraction. Sherrington's 1906 The Integrative Action of the Nervous System set out the stimulus-and-response framework of the reflex and introduced the adequate stimulus, the particular form of energy a given receptor is built to detect. Here the referent is a physical or chemical agent measured by its intensity and duration against a tissue's threshold, unlike the behavioural cue studied in learning or the spending injection studied in economics.[1]

Unit

One applied change in energy or chemistry, scaled by intensity and duration

Recovery means

After firing, the tissue passes through a refractory period before it can be excited again

Measured by

Quantified by threshold, intensity, and duration, and read off the nerve or muscle response it evokes

In behavioural psychology a stimulus is an environmental event defined by its relation to behaviour rather than by its physical energy. Pavlov's 1927 Conditioned Reflexes showed that a neutral event paired with food comes to elicit a response and named it the conditioned stimulus, and Skinner's 1938 The Behavior of Organisms added the discriminative stimulus, an event that signals when a response will be reinforced. The referent is an event classified by the behaviour it controls, so the same physical thing can be a stimulus for one organism and not for another, unlike the threshold-defined agent of physiology or the demand injection of economics.[2][3]

Unit

One event classified by the response it elicits or occasions

Recovery means

An extinguished conditioned response can return after a rest, a pattern Pavlov called spontaneous recovery

Measured by

Measured by the probability, rate, or latency of the response it comes to control

In macroeconomics stimulus is a deliberate increase in government spending, a tax reduction, or central-bank easing meant to raise total spending in a weak economy. Keynes's 1936 The General Theory of Employment, Interest and Money argued that in a downturn public expenditure can raise output and employment by more than the amount spent, an effect later measured as the fiscal multiplier by Auerbach and Gorodnichenko (2012). The referent is a policy injection scaled in currency and judged by its effect on output, wholly distinct from a physiological input to tissue or a learned behavioural cue.[4][5]

Unit

A policy injection measured in currency, as spending, tax cuts, or monetary easing

Recovery means

Not applicable

Measured by

Assessed by the fiscal or monetary multiplier, the change in output per unit of stimulus