4. Variable Interval Schedule

Description: The first response after a variable time interval is reinforced.
Produces

• Moderately steady rate of responding and
• No (or only small) post-reinforcement pause.
• High resistance to extinction

Examples in natural environments:

• A parent attending to the cries of a child. Parents will not typically attend to the child each time it cries, but will leave he or she to fuss for a period before attending.
• Checking voicemail. Calls can arrive at any time so there is a variable interval between each voicemail received.
• Fishing. If you just cast your hook and wait, fishing operates on a variable interval basis. However, if you have to cast several times to catch a fish, this is more like a duration schedule (see below).

Examples in video games:

• Waiting for monsters to re-spawn in a game where respawning occurs at variable intervals. Note: In multiplayer games other players may be waiting for the monster to re-spawn as well, in which case there is a variable interval, limited hold schedule (see below).
• Checking for mail messages from other players.