Experienced social partners hinder learning performance in naive clonal fish

Abstract

Social learning can facilitate information spread within groups and is generally assumed to increase learning efficiency in animals. Here, we asked how individual learning is affected by skill level of a demonstrator present during learning. We predicted that both task-naive and task-experienced individuals benefit from a task-experienced, conspecific demonstrator. We used the all-female clonal Amazon molly (Poecilia formosa) for our experiments. We further propose a model framework which lets us directly relate each research question to a single model parameter. First, following a classical conditioning paradigm over five days, half the fish were trained to find food inside a cylinder, while the others were provided with food randomly dispersed in their tank. As a result trained individuals visited the cylinder with a higher likelihood than randomly fed individuals and showed consistent individual differences in their learning performance. In a second step, we allowed these fish to observe a conspecific while we continued (for those trained) or started (for naives) individual training. We found that trained individuals did not benefit from a partner, regardless of the partners' proficiency, but showed higher average performances compared to naives. Naive individuals showed a decrease in learning performance when paired with experienced partners but not when paired with other naive ones. Our results suggest that Amazon mollies learn a foraging task individually and differ consistently in their individual learning ability. Further, social learning depends on own, as well as the demonstrator's skill level in a way that observing informed conspecifics may hamper own learning.