In humans, a distinction can be made between implicit or procedural learning (involving stimulus-response associations) and explicit or declarative learning (involving verbalizable rules) that is relatively easy to make in verbal humans. According to several investigators, it is also possible to make such a distinction in nonverbal animals. One way is by training them on a conditional discrimination task (e.g., matching-to-sample) in which reinforcement for correct choice on the current trial is delayed until after a choice is made on the next trial – a method known as the 1-back procedure. According to Smith, Jackson, and Church ( Journal of Comparative Psychology, 134(4), 423–434, 2020), the delay between the sample-correct-comparison response on one trial and reinforcement obtained on the next trial is too long for implicit (associative) learning. Thus, according to this theory, learning must be explicit. In the present experiments we trained pigeons using the 1-back procedure. In Experiment 1, pigeons were trained on red/green 1-back matching using a non-correction procedure. Some of the pigeons showed significant learning. When a correction procedure was introduced, all the pigeons showed evidence of learning. In Experiment 2, new pigeons learned red/green 1-back matching with the correction procedure. In Experiment 3, new pigeons learned symbolic 1-back matching with yellow and blue conditional stimuli and red/green choice stimuli. Thus, pigeons can learn using 1-back reinforcement. Although it would appear that the pigeons acquired this task explicitly, we believe that this procedure does not adequately distinguish between implicit and explicit learning.

在人类中，可以区分隐性或程序性学习（涉及刺激-反应关联）和显性或陈述性学习（涉及可口头表达的规则），这在口头人类中相对容易进行。根据几位研究人员的说法，在非语言动物中也可以做出这样的区分。一种方法是通过条件判别任务（例如，与样本匹配）训练他们，其中将当前试验中正确选择的强化延迟到下一次试验做出选择之后——这种方法称为1-回程。根据 Smith、Jackson 和 Church 的说法（比较心理学杂志，134(4), 423–434, 2020)，一次试验的样本正确比较响应与下一次试验获得的强化之间的延迟对于隐式（联想）学习来说太长了。因此，根据这一理论，学习必须是明确的。在目前的实验中，我们使用 1-back 程序训练鸽子。在实验 1 中，使用非校正程序对鸽子进行红/绿 1-back 匹配训练。一些鸽子表现出显着的学习。当引入纠正程序时，所有的鸽子都表现出学习的迹象。在实验 2 中，新鸽子通过校正程序学习红/绿 1-back 匹配。在实验 3 中，新鸽子学习了符号 1-back 匹配与黄色和蓝色条件刺激和红色/绿色选择刺激。因此，鸽子可以使用 1-back 强化来学习。