Reinforcement frequency and contingency as factors in fixed-ratio behavior.

Killeen (1969) looked at how the link between work and reward shapes fixed-ratio responding.

Birds pecked on tandem FR schedules. Extra FR links were added without changing how often food came.

The team asked: does faster reward or tighter work-reward link control the speed of later pecks?

Pause after food stayed the same no matter how many extra FR links were tucked in.

But the final burst of pecks got faster as the tandem requirement grew.

It is the contingency, not the reward rate, that pushes terminal response rate up.

Jones et al. (1992) extends this idea. They showed pause length also tracks the size of the last reward and cues for the next one.

Matthews et al. (1987) seems to disagree. Contingent moves to richer food raised rate yet gave no extra grit against extinction.

The gap is about what "strength" means. Killeen (1969) looks at within-session speed; Matthews et al. (1987) looks at resistance to later extinction. Both can be true.

Lattal (1975) and Crowley (1979) later treat the contingency itself as a signal birds can tell apart, building on the same core idea.

When you build a fixed-ratio program, do not just count how often reinforcement happens. Check that each response clearly earns it. If the work-reward link feels loose, you may get slow, sloppy terminal bursts even with dense pay. Tighten the contingency first; rate will follow.