In my response I revisit the question whether internalization should be conceived as representation or as instantiation. Shepard's ingenuity lies partly in allowing both interpretations. The down side of this facile generality of internalization is its immunity to falsification. I describe evidence from 3-D apparent motion studies that speak against geodesic paths in cases of underspecified percepts. I further reflect on the applicability of internalization to normal, well-specified perception, on the superiority of Gestalt principles, as well as on the evolutionary and developmental implications of the concept. The commentaries to the target article reveal an astonishing lack of agreement. This not only indicates that a satisfactory unifying theory explaining perception in the face of poorly specified stimuli does not exist. It also suggests that for the time being we have to be pluralistic and should treat internalization as a source of inspiration rather than as an irrefutable theory.

The selectionist account of behavior is actually a focused discussion of operant selection. To this end, the authors essentially exclude stimuli from their analysis. This exclusion is inconsistent with the importance placed on environmental interaction in their general account. Further, this exclusion limits the generality of their account by missing important sources of stimulus-elicited behavior (e.g., classical conditioning).

Behaviorism is a dead doctrine that was abandoned for good reason. A major strand of O'Regan & Noë's view turns out to be a type of behaviorism, though of a non-standard sort. However, their view succumbs to some of the usual criticisms of behaviorism.

We provide additional support for Cowan's claim that short term memory (STM) involves a range of 3–5 tokens, on the basis of language correlational analyses. If language is at least partly learned, linguistic dependency structure should reflect properties of the cognitive components mediating learning; one such component is STM. In this view, the range over which statistical regularity extends in ordinary text would be suggestive of STM span. Our analyses of eight languages are consistent with STM span being about four chunks.

Studies of animal culture have not normally included a consideration of cetaceans. However, with several long-term field studies now maturing, this situation should change. Animal culture is generally studied by either investigating transmission mechanisms experimentally, or observing patterns of behavioural variation in wild populations that cannot be explained by either genetic or environmental factors. Taking this second, ethnographic, approach, there is good evidence for cultural transmission in several cetacean species. However, only the bottlenose dolphin (Tursiops) has been shown experimentally to possess sophisticated social learning abilities, including vocal and motor imitation; other species have not been studied. There is observational evidence for imitation and teaching in killer whales. For cetaceans and other large, wide-ranging animals, excessive reliance on experimental data for evidence of culture is not productive; we favour the ethnographic approach. The complex and stable vocal and behavioural cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans, and represent an independent evolution of cultural faculties. The wide movements of cetaceans, the greater variability of the marine environment over large temporal scales relative to that on land, and the stable matrilineal social groups of some species are potentially important factors in the evolution of cetacean culture. There have been suggestions of gene-culture coevolution in cetaceans, and culture may be implicated in some unusual behavioural and life-history traits of whales and dolphins. We hope to stimulate discussion and research on culture in these animals.

Pessoa et al. (1998a) summarize a wide body of data suggesting that perceptual filling-in phenomena can be attributed to neural filling-in processes. However, they reject, on philosophical grounds, the hypothesis that filled-in representations in the brain are the immediate substrate of visual percepts. It is proposed in this commentary that resonant binding between distributed cortical areas may instead be the crucial ingredient for conscious visual percepts, and that filling-in processes may facilitate the interactions between behaving organisms and object surfaces. These suggestions circumvent some of the philosophical problems associated with the idea of localized visual representations.

Many analogies exist between the process of evolution by natural selection and of learning by reinforcement and punishment. A full extension of the evolutionary analogy to learning to include analogues of the fitness, genotype, development, environmental influences, and phenotype concepts makes possible a single theory of the learning process able to encompass all of the elementary procedures known to yield learning.

(1) The main issue with regard to modal and amodal completion is not which phenomena are cognitive, and which perceptual. At the level of the animal, both are visuo-cognitive. At the level of visual processing, however, we need to dissect the different functional effects of these kinds of completion. (2) Resonant binding between distributed cortical areas may play a role in perceptual completion, but evidence is needed.

We reply to Gerbino, Heschl, Hoffman, Jacobs et al., Kurthen, O'Brien & Opie, Todorovic, and Wilson. Several issues are clarified. We concede little.

Human hyperculture appears to have been produced by the amplification of the kind of normal culture shared by cetaceans and other animals and presumably by our ancestors. Is there any possibility that cetaceans could be subject to these amplifying processes, which may include: sexual selection; within-group moral behavior; culling of low- cultural-capacity individuals through predation or self-predation; and reciprocal positive feedback between culture and the capacity for culture.

We suggest a neurophysiological account of the short-term memory capacity limit based on a model of visual working memory (Raffone & Wolters, in press). Simulations have revealed a critical capacity limit of about four independent patterns. The model mechanisms may be applicable to working memory in general and they allow a reinterpretation of some of the issues discussed by Cowan.

O'Regan & Noë make plausible that perception involves mastery of sensory-motor dependencies. Their rejection of qualia, however, is less persuasive; as is their view that we see only what we are attending to. At times they seem to oppose “internal representation” in general; I argue that they should in fact only be rejecting crude conceptions of brain picturing.

The capacity of visual attention/STM can be determined by change-detection experiments. Detecting the presence of change leads to an estimate of 4 items, while detecting the absence of change leads to an estimate of 1 item. Thus, there are two magical numbers in vision: 4 and 1. The underlying limits, however, are not necessarily those of central STM.

While applauding the bulk of the account on offer, we question one apparent implication, namely, that every difference in sensorimotor contingencies corresponds to a difference in conscious visual experience.

Hull et al. rightly point out the special character of selection as a causal mode, but ironically they seem to force selection back into traditional causal modes by decomposing it into replication, variation, and environmental interaction. Many processes are selective, and a taxonomy of a broad range of kinds of selection may be preferable to narrowing the applicability of the term.

Heyes's (1998) skepticism about theory of mind (ToM) in nonhuman primates exploits the idea of a strong and unified theory of mind in humans based on an unanalyzed category of mental state. It also exploits narrow debates about crucial observations and experiments while neglecting wider evolutionary trends. I argue against both exploitations.

Rendell and Whitehead's thorough review dispels notions that culture is an exclusive faculty of humans and higher primates. We applaud the authors, but differ with them regarding the evolution of cetacean culture, which we argue resulted from the availability of abundant but spatially and temporally patchy prey such as schooling fish. We propose two examples of gene-culture coevolution: (1) acoustic abilities and acoustic traditions, and (2) transmission of environmental information and longevity.

By and large the commentators express reservations similar to my own concerning Shepard's position. Some focus on the issue of ecological validity, others are skeptical of Shepard's evolutionary thesis. The assumptions and reasons for their criticisms, however, are not always ones I fully accept. In addition, several commentators, although rejecting Shepard's particular claims, support his overall approach. They offer models for motion perception and for phenomena in other domains that they feel are amenable to treatment along Shepard's lines. I examine the pros and cons of the commentators' analyses of Shepard. I also briefly evaluate aspects of their alternative proposals.

In their account of learning and behavior, the authors define an interactor as emitted behavior that operates on the environment, which excludes Pavlovian learning. A unified neural-network account of the operant-Pavlovian dichotomy favors interpreting neurons as interactors and synaptic efficacies as replicators. The latter interpretation implies that single-synapse change is inherently Lamarckian.

This commentary makes two rejoinders to O'Regan & Noë. It clarifies the status of visual representations in their account, and argues that their explanation of the (according to them, illusory) appeal of qualia is unsatisfying.