Many owners say: “But my dog just wants to say hi!”. It seems harmless to allow the occasional on-lead greeting, but psychology tells us that “sometimes” is one of the most powerful ways to reinforce behaviour.

In fact, the same science that explains why gamblers can’t walk away from a slot machine explains why dogs keep pulling towards other dogs—even if they are only rewarded with a greeting once in a while.

The Slot Machine Effect in Dog Training

Variable-Ratio Reinforcement

Psychologists have shown that when rewards arrive on a variable-ratio schedule (after an unpredictable number of attempts), behaviour becomes highly persistent and very resistant to extinction (Ferster & Skinner, 1957; Mazur, 1983).

This is exactly how gambling machines work—most pulls don’t win, but every so often they pay out, which keeps the gambler coming back.

For dogs, every on-lead greeting becomes a jackpot. Even if your dog only “wins” once in twenty walks, they will still keep pulling—because this time might be the lucky one (Case, 2022).

Behavioural Momentum

Nevin and Grace (2000) describe behavioural momentum: once a behaviour has been reinforced, especially intermittently, it develops resistance to change. Even if you later stop allowing greetings, the pulling persists because of the momentum built from past “jackpots.”

Why This Matters on Walks

  • Allowing greetings “sometimes” creates a gambling mindset in your dog.
  • The behaviour (pulling, lunging, whining) becomes stronger, not weaker.
  • This makes walks frustrating for owners and stressful for dogs.

The Better Way

  • Be consistent: on lead = no greetings.
  • Provide safe, structured off-lead opportunities for socialising instead.
  • Reinforce calm lead walking and attention to you—make those the predictable rewards your dog can count on.

References

Case, L. (2022). Schedules of reinforcement for dogs. American Kennel Club. Retrieved from https://www.akc.org/expert-advice/training/schedules-of- reinforcement-for-dogs/

Ferster, C. B., & Skinner, B. F. (1957). Schedules of Reinforcement. New York: Appleton-Century-Crofts.

Mazur, J. E. (1983). Steady state performance on fixed, mixed, and random ratio schedules. Journal of the Experimental Analysis of Behaviour, 39(2), 293–307.

Nevin, J. A., & Grace, R. C. (2000). Behavioural momentum and the law of effect. Behavioural and Brain Sciences, 23(1), 73–130.