Auditory discrimination learning in zebra finches: effects of sex, early life conditions and stimulus characteristics

A meta-analysis was conducted to investigate whether sex differences, developmental history, stimulus number and/or characteristics affect the speed of auditory discrimination learning of zebra finches, Taeniopygia guttata, as tested in a Go/No-go task. Our results indicate that sex, early life conditions (brood size and juvenile body size), the number of stimuli, type of stimuli (constructed from zebra finch song elements or human speech syllables) and type of discrimination (based on phonetic characteristics or sequential structure of sounds) significantly influenced learning speed. Learning speed was faster if birds were female, reared in larger broods or were larger as juveniles. Greater numbers of stimuli and human speech-based stimuli were harder to learn than fewer stimuli and stimuli consisting of zebra finch song elements. Stimuli differing in phonetic characteristics were learned faster than those varying in structure. Additionally, there was some evidence of stable individual differences in performance across experiments. Our findings demonstrate that discrimination learning can be affected by factors that have been suspected to, but not yet definitively shown to, have impacts on learning. We suggest that examining the learning process itself in more detail by quantifying individual differences in learning strategies may provide more information on how various factors affect variation in learning abilities.