Where does facilitation collide?

Triplett's 1898 study The dynamogenic factors in pacemaking and competition reported that cyclists rode faster alongside others than alone and that children wound a fishing reel more quickly when paired with a co-actor, the first measured account of how the presence of other people changes an individual's performance. Zajonc's 1965 Social facilitation refined this into a general theory: the presence of others raises arousal, which strengthens the most likely response, so performance improves on well-learned tasks and worsens on unfamiliar ones. The referent here is a change in a person's task performance caused by an audience or by co-actors, scored in speed or accuracy, not a boost at a nerve terminal or a benefit one organism confers on another.[1][2]

Unit

One person's performance on a task, with and without others present

Recovery means

Not applicable

Measured by

Compared across alone versus co-action or audience conditions, using task speed, output, or error rates

Feng's 1941 studies of the neuromuscular junction described that when a nerve is stimulated in rapid succession, each later impulse releases more transmitter and produces a larger response than the first, an early account of what became known as facilitation. Katz and Miledi's 1968 The role of calcium in neuromuscular facilitation showed that this short-lived strengthening depends on calcium left over in the nerve ending from the preceding impulse. The referent is a brief, activity-dependent increase in the strength of a single synapse, read from the size of the postsynaptic response, not a shift in a person's behavior before an audience or a helpful interaction between species.[3][4]

Unit

The increase in a synapse's postsynaptic response to a second stimulus arriving soon after the first

Recovery means

The added strength decays within tens to hundreds of milliseconds as residual calcium is cleared

Measured by

Recorded electrophysiologically as the ratio of the second postsynaptic response to the first during paired or repeated stimulation

Connell and Slatyer's 1977 Mechanisms of succession in natural communities and their role in community stability and organization named the facilitation model of succession, in which early-arriving species alter the environment in ways that let later species establish. Bertness and Callaway's 1994 Positive interactions in communities broadened the idea to positive interactions generally, such as a nurse plant that shades and shelters seedlings that could not otherwise survive an exposed site. The referent is an interaction in which one organism improves conditions for another, counted in the second organism's survival, growth, or abundance, not a performance change in a watched person or a short boost at a nerve terminal.[5][6]

Unit

An interaction in which one organism raises another's survival, growth, or abundance

Recovery means

Not applicable

Measured by

Estimated by comparing a target species' survival, growth, or density with and without the benefactor present