No evidence for a saccadic range effect for visually guided and memory-guided saccades in simple saccade-targeting tasks

International audienceSaccades to single targets in peripheral vision are typically characterized by an undershoot bias. Putting this bias to a test, Kapoula [1] used a paradigm in which observers were presented with two different sets of target eccentricities that partially overlapped each other. Her data were suggestive of a saccadic range effect (SRE): There was a tendency for saccades to overshoot close targets and undershoot far targets in a block, suggesting that there was a response bias towards the center of eccentricities in a given block. Our Experiment 1 was a close replication of the original study by Kapoula [1]. In addition, we tested whether the SRE is sensitive to top-down requirements associated with the task, and we also varied the target presentation duration. In Experiments 1 and 2, we expected to replicate the SRE for a visual discrimination task. The simple visual saccade-targeting task in Experiment 3, entailing minimal top-down influence, was expected to elicit a weaker SRE. Voluntary saccades to remembered target locations in Experiment 3 were expected to elicit the strongest SRE. Contrary to these predictions, we did not observe a SRE in any of the tasks. Our findings complement the results reported by Gillen et al. [2] who failed to find the effect in a saccade-targeting task with a very brief target presentation. Together, these results suggest that unlike arm movements, saccadic eye movements are not biased towards making saccades of a constant, optimal amplitude for the task

Egg recognition in Japanese quail

Egg recognition allows birds to reduce the costs of heterospecific or conspecific nest parasitism, by allowing them to reject foreign eggs or abandon parasitised clutches. However, the precise phenotypic characteristics of eggs that are recognised and compared are not well understood. Using Japanese quail (Coturnix japonica), which exhibit extremely high between-female and low within-female variation in egg colour, maculation patterns and shape, I show that females can learn to recognise the salient characteristics of eggs from a given clutch (not necessarily their own) and can use this learned template to discriminate against foreign eggs with a high probability when the eggs are phenotypically distinct. Specifically, female quail appear to use both maculation pattern and, to a lesser extent, egg shape to make these decisions. These findings are discussed with respect to cognitive mechanisms of egg recognition