Four experimentally naïve white Carneau pigeons learned to match three colors to each other in a variant of an Identity matching-to-sample procedure with an FR20 on samples and a response-initiated FI8-s on comparisons. In Experiment 1, the extent to which subjects were matching on the basis of identity was assessed by presenting, in extinction, test trials comprising novel stimuli serving as the sample (and matching comparison) or as the nonmatching comparison. The results from Experiment 1 suggested intermediate or little to no transfer on the basis of identity. Experiment 2 reassessed transfer on the basis of identity with differential reinforcement on the test trials. Under these conditions, two of the four birds demonstrated substantially better than chance levels of performance. These data imply that while the extended response requirements may be necessary, other procedural aspects may be responsible for generalized identity matching in the pigeon.

The starting point of this paper is the observation that methods based on the direct match of keywords are inadequate because they do not consider the cognitive ability of concept formation and abstraction. We argue that keyword evaluation needs to be based on a semantic model of language capturing the semantic relatedness of words to satisfy the claim of the human-like ability of concept formation and abstraction and achieve better evaluation results. Evaluation of keywords is difficult since semantic informedness is required for this purpose. This model must be capable of identifying semantic relationships such as synonymy, hypernymy, hyponymy, and location-based abstraction. For example, when gathering texts from online sources, one usually finds a few keywords with each text. Still, these keyword sets are neither complete for the text nor are they in themselves closed, i.e., in most cases, the keywords are a random subset of all possible keywords and not that informative w.r.t. the complete keyword set. Therefore all algorithms based on this cannot achieve good evaluation results and provide good/better keywords or even a complete keyword set for a text. As a solution, we propose a word graph that captures all these semantic relationships for a given language. The problem with the hyponym/hyperonym relationship is that, unlike synonyms, it is not bidirectional. Thus the space of keyword sets requires a metric that is non-symmetric, in other words, a quasi-metric. We sketch such a metric that works on our graph. Since it is nearly impossible to obtain such a complete word graph for a language, we propose for the keyword task a simpler graph based on the base text upon which the keyword sets should be evaluated. This reduction is usually sufficient for evaluating keyword sets.