Response-independent milk delivery enhances persistence of pellet-reinforced lever pressing by rats.
Free reinforcers that differ from the earned ones still make behavior more persistent during extinction.
01Research in Context
What this study did
Scientists gave rats a lever that paid one food pellet every 100 seconds on average. While the rats worked, a machine also dripped milk into the cage. The milk came no matter what the rat did.
Later the team stopped all food and milk. They counted how many extra lever presses each rat made before quitting.
What they found
Rats that had received free milk kept pressing the lever longer during extinction. The dose of milk and the length of the blackout did not matter. Just pairing the lever light with any extra reward made the behavior stick.
How this fits with other research
Podlesnik et al. (2017) extends this idea. They showed that mixing extra stimuli with the target cue during extinction weakens the cue more. Together the papers say: extra reinforcers build persistence, but extra cues can tear it down.
Aznar et al. (2005) moves the same rule to kids. They gave noncontingent toys during hygiene routines and saw problem behavior drop. Free items still alter behavior, but now the goal is reduction, not persistence.
Neuringer (1969) looks like a contradiction at first. That study found a stimulus linked to no food broke superstitious chains fast. The difference is timing: J paired the light with no food, while A paired it with bonus milk. Same light, opposite message.
Why it matters
Your client may face free reinforcers daily: staff attention, vending machines, sibling toys. If these extras happen while the target behavior is occurring, they can make the behavior harder to extinguish later. Watch the environment, not just your program. Either remove the free rewards or fold them into your contingency so you control the message.
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02At a glance
03Original abstract
If, during training, one stimulus is correlated with a higher rate of reinforcement than another, responding will be more resistant to extinction in the presence of that higher rate signal, even if many of the reinforcers have been presented independently of responding. For the present study we asked if the response-independent reinforcers must be the same as the response-dependent reinforcers to enhance the response's persistence. Twelve Long-Evans hooded rats obtained 45-mg food pellets by lever pressing (variable-interval 100-s schedules) in the presence of two discriminative stimuli (blinking vs. steady lights) that alternated every minute during daily sessions. Also, in the presence of one of the stimuli (counterbalanced across rats), the rats received additional response-independent deliveries of sweetened condensed milk (a variable-time schedule). Extinction sessions were exactly like training sessions except that neither pellets nor milk were presented. Lever pressing was more resistant to extinction in the presence of the milk-correlated stimulus when (a) the size of the milk deliveries during training (under a variable-time 30 s schedule) was 0.04 ml (vs. 0.01 ml) and (b) 120-s or 240-s blackouts separated components. Response-independent reinforcers do not have to be the same as the response-dependent reinforcers to enhance persistence.
Journal of the experimental analysis of behavior, 2001 · doi:10.1901/jeab.2001.76-179