Abstract

We trained 8 pigeons (Columba livia) on a stagewise go/no-go visual discrimination task of increasing complexity, to document the dynamics of selective attention. We constructed negative compound stimuli (S-s) on the basis of their overall similarity to a positive compound stimulus (S +) along 4 binary-valued dimensions: shape (circle/square), size (large/small), line orientation (horizontal/vertical), and brightness (dark/light). Starting with 1 S + and 1 S-that differed in all 4 dimensional values, in 3 later steps, we progressively added S-s sharing 1, 2, and finally 3 dimensional values with the S +. Although in the first step the pigeons could have attended to any of the 4 dimensions (separately or together) to solve the discrimination, all of the pigeons attended to only 1 dimension. Furthermore, the pigeons attended to just 1 additional dimension in each of the 3 succeeding steps. Notably, all pigeons discriminated the 4 dimensions in the same order: first brightness, then line orientation, then size, and finally shape. This ordering corresponds with the overall discriminability of the dimensional values for these dimensions observed in prior studies. Pigeons clearly optimized their attentional behavior, selectively and efficiently processing only 1 additional dimension in each stage of discrimination learning.