Identity concept formation during visual multiple-choice matching in a harbor seal (Phoca vitulina).

Identity concept formation was tested in a harbor seal using a visual multiple-choice matching-to-sample task. The seal was first trained on a two-alternative matching task. After criterion (> or =80% correct choices in two successive sessions) was reached with two sets of two stimuli (Figure 3, Blocks A and B), stimulus sets were enlarged to six objects (Blocks C-G). After the seal reached criterion immediately with two successive sets (Blocks F and G), multiple-choice matching was introduced, first using stimulus sets of four familiar objects (Blocks H-M). After the seal reached the criterion immediately with two successive sets (Blocks L and M), completely new objects were used in two further stimulus sets (Blocks N and O). The seal immediately applied the matching rule in all four sessions (> or =80% correct choices). In two further sessions with problems composed of all 38 familiar stimuli, the seal again reached the criterion (Block P). In the final, transfer session, 20 new problems were composed of 80 unknown stimuli (Block Q). The seal immediately applied the matching rule in these one-trial tests, showing that harbor seals can conceptualize complex visual information.