Preferences for fixed and variable food sources: variability in amount and delay.

Scientists tested starlings in a lab. The birds chose between two food sources. One source always gave the same amount after the same wait. The other source changed either the amount or the wait time.

The team kept the average amount and delay equal on both sides. They wanted to see if birds liked surprises in timing or in food size.

Birds liked variable wait times. They picked the option where the delay changed.

But birds did not like variable amounts. They slightly avoided the option where the food size changed.

This shows animals treat time surprises and amount surprises differently.

Fine et al. (2005) found the same pattern in pigeons. Both studies show weak preference for fixed delays when the average stays the same.

Soreth et al. (2009) added that birds like variable delays even more when short delays happen more often. This helps explain why the starlings chose variable timing.

Mueller et al. (2000) tested rats with variable food amounts. They found rats flip their choice based on how hungry they are. This shows amount variability is risky, matching the starlings' weak avoidance.

Doughty et al. (2010) showed humans and pigeons both pick variable delays when tokens trade right away. This makes the starling finding more useful for people.

When you use variable schedules, think about what is changing. Kids may like variable timing if it sometimes means faster reinforcement. But they may dislike variable amounts if it means smaller rewards. Start with variable time schedules, keep reward size steady, and watch how your learner responds.