 Mental process

A mental process is an activity involved in cognition, such as allocating attention, interpreting a sensory pattern, retrieving human memory or selecting a response. The process is an explanatory construct: a keypress or spoken answer is an observation used to investigate it, not a direct measurement of every internal step.

Saul Sternberg tested whether a presented symbol belonged to a short memorized set. His 1966 study found that mean reaction time increased approximately linearly with set length and interpreted the pattern in terms of rapid internal comparisons.^[ref]

An invented model illustrates the reasoning. Suppose $T(n)=a+bn$, where $n$ is set size, $a=300\mathrm{ms}$ and $b=40\mathrm{ms}$ per item. Then $T(2)=380\mathrm{ms}$ and $T(5)=500\mathrm{ms}$. The intercept can summarize operations whose duration does not vary with $n$, while the slope summarizes the measured size effect. These values are illustrative, not Sternberg's reported estimates.

A good fit establishes a pattern that a proposed mental process can explain; it need not uniquely establish that process. Changes in attention, response strategy or other operations may also affect reaction time. Comparing predictions across controlled conditions makes the inference stronger than naming an internal activity after one measured response.