Types of measure: latency, frequency, duration and intensity

Behavioural observations most commonly yield four basic types of measure.

1 Latency (measured in units of time; e.g., s, min or h) is the time from some specified event (for example, the beginning of the recording session or the presentation of a stimulus) to the onset of the first occurrence of the behaviour. For example, if a rat presses a lever for the first time 6 min after it is placed in a Skinner box, the latency to press the lever is 6 min. (See Fig. 5.1.)

If, as is normally the case, the period of observation is limited and each individual is tested more than once, then the behaviour pattern may not occur at all during some tests. This makes it impossible to calculate a simple average latency for each individual, although there are methods of combining repeated latency measures into an overall score for each subject (e.g., Theobald & Goupillot, 1990).

2 Frequency (measured in reciprocal units of time; e.g., s-1, min-1 or h-1) is the number of occurrences of the behaviour pattern per unit time. Frequency is a measure of the rate of occurrence. For example, if a rat presses a lever 60 times during a 30-min recording session, the frequency of lever pressing is 2 min-1. (See Fig. 5.1.)

An alternative usage, which is perhaps more common in the behavioural literature and in statistics, is when ‘frequency’ refers to the total number of occurrences.