Evidence from studies of the processing of topographic and classifier constructions in sign language sentences provides a model of how a mental scene description can be represented linguistically, but it also raises questions about how this can be related to spatial linguistic descriptions in spoken languages and their processing. This in turn provides insights into models of the evolution of language.

It is necessary to distinguish among representations caused directly by perception, representations of past perceptions in long-term memory, the representations underlying linguis- tic utterances, and the surface phonological and grammatical structures of sentences. The target article dealt essentially with predicate-argument structure at the first of these levels of representation. Discussion of the commentaries mainly involves distinguishing among various applications of the term “predicate”; clarifying the assumed relationship between classical FOPL and language; clarifying the status of unique individuals as conceived by humans; and addressing the issues of motion-perception, binding between object-percepts and predicate-percepts, and target-driven versus stimulus-driven attention.

Researchers have begun to explore animals' capacities for uncertainty monitoring and metacognition. This exploration could extend the study of animal self-awareness and establish the relationship of self-awareness to other-awareness. It could sharpen descriptions of metacognition in the human literature and suggest the earliest roots of metacognition in human development. We summarize research on uncertainty monitoring by humans, monkeys, and a dolphin within perceptual and metamemory tasks. We extend phylogenetically the search for metacognitive capacities by considering studies that have tested less cognitively sophisticated species. By using the same uncertainty-monitoring paradigms across species, it should be possible to map the phylogenetic distribution of metacognition and illuminate the emergence of mind. We provide a unifying formal description of animals' performances and examine the optimality of their decisional strategies. Finally, we interpret animals' and humans' nearly identical performances psychologically. Low-level, stimulus-based accounts cannot explain the phenomena. The results suggest granting animals a higher-level decision-making process that involves criterion setting using controlled cognitive processes. This conclusion raises the difficult question of animal consciousness. The results show that animals have functional features of or parallels to human conscious cognition. Remaining questions are whether animals also have the phenomenal features that are the feeling/knowing states of human conscious cognition, and whether the present paradigms can be extended to demonstrate that they do. Thus, the comparative study of metacognition potentially grounds the systematic study of animal consciousness.

Metacognitive knowledge of one's own cognitive states is not as useful as is often thought. Differences between cognitive states often come down to differences in their intentional contents. For that reason, differences in behaviour are often explained by differences just in contents of first-order states. Uncertainty need not be a metacognitive condition. First-order interpretations of the target experiments are available.

Smith et al.'s article provides a convincing argument for devoting increased research attention to comparative metacognition. However, this increased attention should be complemented with establishing links with comparative theory of mind (ToM) research, which are currently missing. I present a task in which pairs of subjects are presented with incomplete information in an object-choice situation that could be used to establish that link.

In this commentary, we raise two issues. First, we argue that in any species, the comparative study of metacognitive abilities must be approached from a developmental perspective and not solely from the adult end state. This makes it possible to explore the trajectories by which different species reach their phenotypic outcome and whether different cognitive systems interact over developmental time. Second, using our research comparing different genetic disorders in humans, we challenge the authors' claim that it is unparsimonious to interpret the same performance in humans and animals in qualitatively different ways, because even the same overt behaviour in different groups of humans can be sustained by different underlying cognitive processes.

Smith et al. present us with a false dichotomy in explaining their uncertainty data: Either the animals' responses are “under the associative control of stimulus cues,” or the animals must be responding “under the metacognitive control of uncertainty cues.” There is a third alternative to consider: one that is genuinely cognitive, neither associative nor stimulus driven, but purely first-order in character. On this alternative the metacognitive reports of humans in these situations reflect states that are interpretative rather than causal in character.

The target authors make a strong case for parallels between human and nonhuman metacognition. The case may be bolstered by an appeal to the literatures on commitment and self-control and to that on observing behavior.

Three types or levels of uncertainty monitoring are distinguished: (1) uncertainty responding but no feelings of uncertainty, (2) conscious feelings of uncertainty, (3) conscious feelings of uncertainty plus reflective awareness of what these feelings are and mean. It is hypothesized that only the first and perhaps the second occur in animals and human infants, whereas all three occur in older humans. Two possible lines of future research are also suggested.

In animals' natural lives, uncertainty is normal; and certainty, exceptional. Evaluating ambiguous information is essential for survival: Does what is seen, heard, or smelled mean danger? Does that gesture mean aggression or fear? Is he confident or uncertain? If they are conscious of anything, the content of animals' awareness probably includes crucial uncertainties, both their own and those of others.

Smith et al. show that monkeys and dolphins can respond adaptively under conditions of uncertainty, suggesting that they monitor subjective uncertainty and control their behavior accordingly. Drawing on our own work with humans on the strategic regulation of memory reporting, we argue that, so far, the distinction between monitoring and control has not been addressed sufficiently in metacognitive animal research.

Metacognition is either direct, as when information is recalled before making a confidence judgment, or indirect, as when the probability of successful future retrieval is determined inferentially. Direct metacognition may require an explicit mental representation as its object and can only be demonstrated under specific experimental circumstances. Other forms of metacognition can be based on publicly observable stimuli rather than introspection.

The uncertainty response adds an important new dimension to conventional animal learning and memory studies. Although the uncertainty response by monkeys and dolphins resembled that of humans, parsimony alone does not necessarily indicate that the monkeys and dolphins had a full self-awareness. However, the uncertain response may be an index of an evolutionary precursor to full self-awareness of uncertainty and a theory of mind.

Smith et al. propose that the most parsimonious explanation for identical responses of humans and nonhumans under the same conditions is not always the simplest cognitive explanation but could be the one that has the most logical consistency across species. The authors provide convincing evidence and a reasonable argument for declarative consciousness as a shared psychological property in humans, monkeys, and dolphins.

The very clever studies reviewed by Smith et al. convincingly demonstrate metacognitive skills in animals. However, interpreting the findings on metacognitive monitoring as showing conscious cognitive processes in animals is not warranted, because some metacognitive monitoring observed in humans appear to be automatic rather than controlled.

Several conclusions depend on a version of signal detection theory that assumes performance is based on underlying equal-variance normal distributions of trace strength. Such conclusions are questionable without empirical justification for that assumption. A thought experiment is presented to show how the assumption is probably invalid, and empirical evidence is cited for the assumption's invalidity in research on human memory.

Only two of the many experiments described by Smith et al., as indicating metacognitive ability in nonhuman animals, involved metacognition as understood in the human literature. Of these, one gave negative results. In the other, one of two rhesus monkeys provided data suggesting that he might have metacognitive ability. The conjecture that any nonhuman animals have metacognitive ability is, therefore, tenuous.

Against the view that metacognition is a capacity that parallels theory of mind, it is argued that metacognition need involve neither metarepresentation nor semantic forms of reflexivity, but only process-reflexivity, through which a task-specific system monitors its own internal feedback by using quantitative cues. Metacognitive activities, however, may be redescribed in metarepresentational, mentalistic terms in species endowed with a theory of mind.

We suggest that the phenomenon of uncertainty monitoring in nonhuman animals contributes richly to the conception of nonhuman animals' self-monitoring. We propose that uncertainty may play a role in the emergence of new forms of behavior that are adaptive. We recommend that Smith et al. determine the extent to which the uncertain response transfers immediately to other test paradigms.

When animals choose between completing a cognitive task and “escaping,” proper interpretation of their behavior depends crucially on methodological details, including how forced and freely chosen tests are mixed and whether appropriate transfer tests are administered. But no matter how rigorous the test, it is impossible to go beyond functional similarity between human and nonhuman behaviors to certainty about human-like consciousness.