Wright Lab


Monkey & Pigeon Same/Different Abstract-Concept Learning

We have studied how rhesus monkeys, capuchin monkeys and pigeons learn the same/different abstract concept. The same/different concept is THE basic building block of virtually all abstract thought. Central issues include which species have the cognitive ability to learn same/different abstract concepts. We have shown that monkeys and pigeons have this ability and show qualitatively similar learning of this abstract concept; their transfer to novel pictures increases as a function of the training set size and eventually is equivalent to their baseline training performances (see Wright & Katz 2006 for training and transfer pictures and a summary of this work).

We have shown that this abstract-concept learning cannot be due to simple stimulus generalization (Wright & Katz 2007). There is however a quantitative species difference (see figure on this page). Pigeons require more exemplars of the abstract concept (i.e., more training stimuli) to learn it. This difference we characterize as a quantitative difference. A quantitative difference, we argue, is not a difference in the basic learning ability and is certainly not due to the absence of a so-called cognitive module (inherited neural apparatus though evolution) as many scientists have thought. Indeed, we have shown that the greater number of exemplars required by pigeons to learn the abstract S/D concept is due to carryover effects of learning the task with small numbers of exemplars that interfere with future learning (Nakamura, Wright, et al).

The early training with small training sets restricts the domain of relational learning on which abstract-concept learning is based. We have shown this domain restricted relational learning with special training and testing procedures. In addition to showing domain-restricted relational learning and how it affects concept learning, we have shown that “when concept learning fails” relational learning occurs in the S/D task albeit with a restricted domain (submitted ms). This finding is in stark contrast to the popular opinion (more than half a century) that when concept learning fails—the subjects (animals, children) learn the task item-specifically, not relationally.

Memory Research

Pigeons, rhesus monkeys, capuchin monkeys and humans have been trained and tested in visual list-memory tasks with sequences of four “travel” pictures for animals or four kaleidoscope pictures for humans (Wright, Santiago, et al., 1985) and were tested with one test item each trial. Visual recency (last item) memory diminished with retention delay, and primacy (first item) memory strengthened. Rhesus monkeys, Capuchin monkeys, pigeons, and humans (Wright, 1999) all showed similar visual-memory changes but the changes from visual recency to visual primacy were faster for pigeons than for monkeys and the monkey changes were faster than for humans (Wright, 1998).

Repeating visual items from prior lists (Jitsumori, Wright, et al., 1988) produced interference (on non-matching tests) revealing how far back memory extended. The possibility of using the interference function to separate familiarity vs. recollective memory processing is discussed.

Rhesus monkeys were trained and tested in an auditory list memory task with musical passages. They showed octave generalization (Wright, Rivera, et al., 2000) for some lists of notes—tonal, but not atonal, musical passages. Rhesus monkeys were also trained with four natural/environmental sounds followed by single test items. In contrast with visual list memory, auditory primacy memory (Wright, 1998) diminished with delay and auditory recency memory strengthened. Manipulations of inter-item intervals, list length, and item presentation frequency revealed proactive and retroactive inhibition among items of individual auditory lists (Wright & Roediger, 2003).