Learning and Judgment Can Be Affected by Predisposed Fearfulness in Laying Hens

Abstract

High fearfulness could disrupt learning and likely affects judgment in animals, especially when it is part of an animals' personality, i.e., trait anxiety. Here, we tested whether high fearfulness affects discrimination learning and judgment bias (JB) in laying hens. Based on the response to an open field at 5 weeks of age, birds were categorized as fearful (FC) by showing no walking or vocalizing or non-fearful (NFC) by showing walking and vocalizing. At adult age, birds (n = 24) were trained in a go-go task to discriminate two cues (white or black) with a small or large reward. Birds that reached training criteria were exposed to three unrewarded ambiguous cues (25, 50, and 75% black) to assess JB. Task acquisition took longer for FC birds than for NFC birds, due to a left side bias, and more sessions were needed to unlearn this side bias. Changes in trial setup increased response latencies for FC birds but not for NFC birds. A larger number of FC birds than NFC birds chose optimistically in the last ambiguous trial (25% black). FC birds had a longer latency to choose in the ambiguous trial (75% black) compared to NFC birds. Prior choice in ambiguous trials and a preceding large or small trial affected latencies and choices for both types of birds. Our study showed that fearfulness was associated with differences in discrimination learning ability and JB. It appeared that FC birds used a rigid response strategy during early learning phases by choosing a specific side repeatedly irrespective of success. FC birds were more affected by changes in the setup of the trials in comparison to NFC birds. We speculate that FC birds are more sensitive to changes in environmental cues and reward expectancy. These factors could explain how high fearfulness affects learning.

Uninhibited chickens: ranging behaviour impacts motor self-regulation in free-range broiler chickens ( Gallus gallus domesticus )

“…The environmental complexity of different housing conditions and internal factors such as sex, breed and animal personality are known to affect an individual's behaviour, brain morphology and cognitive abilities [14,[40][41][42][43][44]. In our study, animals living under the same conditions but with different propensities to range showed different levels of motor self-regulation.…”

More Than Eggs – Relationship Between Productivity and Learning in Laying Hens

“…It was randomly selected, whether a hen learned that red or green was the rewarded color. Furthermore, the side of the screen on which the rewarded bar appeared was randomized, to avoid side preferences ( de Haas et al, 2017a , b ). Pecking on the black screen was neither rewarded nor counted as a wrong decision.…”

Peer Review #1 of "Application of open field, tonic immobility, and attention bias tests to hens with different ranging patterns (v0.1)"

“…Previous measurements of cognitive and learning abilities that require bird training have excluded hens that do not make training criterion due to lack of movement (Campbell et al, 2018;Krause et al, 2006;Nordquist et al, 2011). Similarly, previous tests of judgement bias have shown fearful hens were less flexible during task learning than non-fearful hens (fearfulness was assessed in an open field test; de Haas et al, 2017). Unfortunately, these non-moving/learning individuals are likely informative to the questions being asked, but logistically cannot be assessed further, removing potentially vital subjects.…”

“…Additionally, the results can be contextually variable and inconsistent. Chicks in an isolation-induced anxious state showed a pessimistic bias towards visual predator cues (owl silhouette; Salmeto et al, 2011) but socially-isolated adult hens showed no judgement bias towards ambiguous food reward cues (Hernandez et al, 2015) and individual differences in fearfulness can affect the ability of hens to learn judgement bias tasks (de Haas et al, 2017). Unexpected findings have been reported with an optimistic bias found in response to environmentally-induced chronic stress (Verbeek et al, 2019) and pharmacologically-induced chronic stress did not influence judgement bias in sheep (Monk et al, 2019).…”