de Haas Elske N, Lee Caroline, Rodenburg T Bas
Behavioural Ecology Group, Wageningen University, Wageningen, Netherlands.
Adaptation Physiology Group, Wageningen University, Wageningen, Netherlands.
Front Vet Sci. 2017 Jul 27;4:113. doi: 10.3389/fvets.2017.00113. eCollection 2017.
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 ( = 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.
高度恐惧可能会干扰动物的学习，并可能影响其判断力，尤其是当它成为动物个性的一部分时，即特质焦虑。在此，我们测试了高度恐惧是否会影响蛋鸡的辨别学习和判断偏差（JB）。根据5周龄时对旷场试验的反应，表现为不行走或不发声的鸡被归类为恐惧型（FC），表现为行走和发声的鸡被归类为非恐惧型（NFC）。成年后，对24只鸡进行了“去-去”任务训练，以辨别两个线索（白色或黑色），并给予小奖励或大奖励。达到训练标准的鸡被暴露于三个无奖励的模糊线索（25%、50%和75%黑色）中，以评估判断偏差。由于左侧偏向，FC鸡完成任务所需的时间比NFC鸡长，并且需要更多的训练次数来消除这种偏向。试验设置的变化增加了FC鸡的反应潜伏期，但对NFC鸡没有影响。在最后一次模糊试验（25%黑色）中，选择乐观的FC鸡比NFC鸡更多。与NFC鸡相比，FC鸡在模糊试验（75%黑色）中的选择潜伏期更长。在模糊试验中的先前选择以及之前的大奖励或小奖励试验会影响两种类型鸡的潜伏期和选择。我们的研究表明，恐惧与辨别学习能力和判断偏差的差异有关。似乎FC鸡在早期学习阶段采用了一种僵化的反应策略，即无论是否成功，都反复选择特定的一侧。与NFC鸡相比，FC鸡更容易受到试验设置变化的影响。我们推测，FC鸡对环境线索和奖励预期的变化更为敏感。这些因素可以解释高度恐惧是如何影响学习的。
