Fading perceptual resemblance: a path for rhesus macaques (Macaca mulatta) to conceptual matching?

Abstract

Cognitive, comparative, and developmental psychologists have long been intrigued by humans' and animals' capacity to respond to abstract relations like sameness and difference, because this capacity may underlie crucial aspects of cognition like analogical reasoning. Recently, this capacity has been explored in higher-order, relational matching-to-sample (RMTS) tasks in which humans and animals try to complete analogies of sameness and difference between disparate groups of items. The authors introduced a new paradigm to this area, by yoking the relational-matching cue to a perceptual-matching cue. Then, using established algorithms for shape distortion, the perceptual cue was weakened and eliminated. Humans' RMTS performance easily transcended the elimination of perceptual support. In contrast, RMTS performance by six macaques faltered as they were weaned from perceptual support. No macaque showed evidence of mature RMTS performance, even given more than 260,000 training trials during which we tried to coax a relational-matching performance from them. It is an important species difference that macaques show so hesitant a response to conceptual relations when humans respond to them so effortlessly. It raises theoretical questions about the emergence of this crucial capacity during humans' cognitive evolution and during humans' cognitive development.

Keywords: Comparative cognition; Concept learning; Primate cognition; Relational matching; Same-different.

Figure 1

Examples of trials from the relational match-to-sample (RMTS) task. Column 1(farthest left): same trials, with the level of perceptual support set at 90, 78, 66, and 54. The definition of these levels of perceptual support is given in the text. Column 2: different trials, at the same four levels of perceptual support. Column 3: same trials, with the levels of perceptual support set at 42, 30, 18, and 0. Column 4 (farthest right): different trials, at the same four levels of perceptual support. For the figure’s clarity, the same and different choice options, respectively, are always shown to the left and right on the bottom of the screen. These positional assignments actually varied randomly for each trial in the RMTS task.

Figure 2

Humans’ performance by 10-trial block in the RMTS task of Experiments 1A (top-left panels), 1B (bottom-left panels), and 1C (top-right and bottom-right panels). In The top panel gives the average level of perceptual support they experienced at each trial block. The definition of these levels of perceptual support is given in the text. The bottom panel gives humans’ proportion correct for trials in each trial block. The red symbols summarized performance for the zero-similarity RMTS trials that offered no perceptual support.

Figure 3

Humans’ performance by 10-trial block in the RMTS task of Experiment 1C. Performance is shown for participants never given any perceptual support before and after their moment of task solution. Block 0 was defined to be the first block at which each participant achieved .80 correct and sustained that performance thereafter. Then, trial blocks were counted forward and backward from that criterion point.

Figure 4

Hank’s performance by 250-trial block in the RMTS task of Experiment 2. The top panel gives the average level of perceptual support Hank experienced at each trial block. The definition of these levels of perceptual support is given in the text. The succession of different tasks that Hank received is indicated by an alternation of filled and open symbols, or by a lapsing of the black symbols during a task method that only presented zero-similarity trials. These specific tasks are described in the text. The concurrent or sole presence of zero-similarity trials—that offered no perceptual support—is indicated by the red symbols at perceptual level 0. The bottom panel gives Hank’s proportion correct for all trials in each trial block, with task alternation indicated as just described. Performance is shown on trials that potentially offered some level of perceptual support (black symbols) and on zero-similarity trials that offered no perceptual support.

Figure 5

Obi’s performance by 250-trial block in the RMTS task of Experiment 2, graphed as described in the caption to Figure 4.

Figure 6

Gale’s performance by 250-trial block in the RMTS task of Experiment 2, graphed as described in the caption to Figure 4.

Figure 7

Murph’s performance by 250-trial block in the RMTS task of Experiment 2, graphed as described in the caption to Figure 4.

Figure 8

Han’s performance by 250-trial block in the RMTS task of Experiment 2, graphed as described in the caption to Figure 4.

Figure 9

Chewie’s performance by 250-trial block in the RMTS task of Experiment 2, graphed as described in the caption to Figure 4. On page 4 in the first sentence, why not take out "weakly" and give the reviewer the point he asked for, which is acknowledgment that pigeons do learn relationally sometimes. I think this is a smart move, too, as this person wanted some of those other papers cited, which we did not do, and I agree that in some other kinds of tasks there is better evidence of relational learning than in the RMTS tasks.