The theory presented here is a near neighbour of Humphrey's theory of sensations as actions. O'Regan & Noë have opened up remarkable new possibilities. But they have missed a trick by not making more of the distinction between sensation and perception; and some of their particular proposals for how we use our eyes to represent visual properties are not only implausible but would, if true, isolate vision from other sensory modalities and do little to explain the phenomenology of conscious experience in general.

Darwin's theory of natural selection is as applicable to the analysis of the behavior of organisms as it is to their origins. Skinner's theoretical writings have guided operant psychologists in this area. The behavioral account of selection by Donahoe and Palmer (1994) is positively compared to the points on operant selection made by Hull et al. The “general account of selection” was found to be useful.

O'Regan & Noë (O&N) argue that there is no need of internal, more or less picture-like, representation of the visual world in the brain. They propose a new approach in which vision is a mode of exploration of the world that is mediated by knowledge of sensorimotor contingencies. Data obtained in “change blindness” experiments support this assumption.

The aim of our commentary is to strengthen Cowan's proposal for an inherent capacity limitation in STM by suggesting a neurobiological mechanism based on competitive networks and nonlinear oscillations that avoids some of the shortcomings of the scheme discussed in the target article (Lisman & Idiart 1995).

Demonstrating cetacean communicative cultures requires documenting vocal differences among conspecific groups that are socially learned and stable across generations. Evidence to date does not provide strong scientific support for culture in cetacean vocal systems. Further, functional analyses with playbacks are needed to determine whether observed group differences in vocalizations are meaningful to the animals themselves.

Vocal imitation does not imply an ability to imitate nonvocal motor patterns. Exponential growth in frequency of a behaviour in a population does not imply diffusion by social learning. Distinguishing analogues from homologues of human culture will avoid confusion in discussion of evolution of culture. Original sources do not demonstrate social learning, imitation, or teaching of intentional beaching or lobtail feeding in cetaceans.

For Gibson, sensory stimulation is neither the cause nor a component of perception, but merely incidental. Perception is based on the pickup of information, which occurs when purposeful observers actively seek information. I present a case in which only with the active sampling of the ambient optical flow field can observers extract the requisite information for the control of locomotion.

Comparing and sharing selectionist terms and concepts from disparate domains can aid understanding in each domain. But constraints of interpretive language will make this difficult – such as the bipolar constraint of interpretive language when addressed to intrinsically tripolar phenomena. Hull et al. acknowledge that some key terms in their account remain problematic; the term, “information,” probably needs to be replaced.

Can we identify individuals with a larger basic capacity than Cowan's proposed limit? Thompson et al. (1993) claimed that Rajan Mahadevan had a basic memory span of 13–15 items. Some of their supporting evidence is reconsidered and additional data are presented from study of another memory expert. More detailed analysis of performance in such cases may yield different conclusions.

The sensorimotor theory of vision successfully blends in with the currently developing action-oriented account of cognition. As a theory of phenomenal consciousness, however, it suffers from the same shortcomings as the theories O'Regan & Noë (O&N) criticize. This is mainly due to the failure to avoid the explanatory gap by rejecting one notion of qualia while retaining the concept of experience with qualitative features in general.

The generic account of selection proposed by Hull et al. readily fits operant learning where, by comparison with natural selection, the process is well understood but little is known about the mechanism. Objections within psychology, that operant learning ignores internal processes, fail to recognise the general significance of behaviour-environment interactions. Variation within operant response classes requires further investigation.

The mechanisms for cultural transmission remain disputable and difficult to validate through observational field studies alone. If controlled experimental laboratory investigation reveals that a putative mechanism is demonstrable in the species under study, then inferences that the same mechanism is operating in the field observation are strengthened.

A primary proposal of the Cowan target article is that capacity limits arise in working memory because only 4 chunks of information can be attended at one time. This implies a single, unitary attentional focus or resource; we instead propose that relatively independent attentional mech- anisms operate within different cognitive subsystems depending on the demands of the current stimuli and tasks.

We review studies that indicate a dissociation between the perceptual estimate and the resulting cognitive representation of given properties of a seen object, on the one hand, and the motor action exerted on the same object. We propose that there exist multiple levels of organization of sensorimotor loops and that internal models may be made accessible to one level of organization while remaining inaccessible to another level.

Seeking parallels among disciplines can have both risks and benefits. Finding parallels may be a vacuous exercise in categorization, generating no new insights. And pointing to analogous functions may cause us to treat them as homologous. Hull et al. have provided a basis for the generation of insights in different selectionist areas, without confusing analogy with homology.

Human beings grow into cultural knowledge, within a social and environmental context, rather than receiving it ready made. This seems also to be true of cetaceans. Rendell and Whitehead invoke a notion of culture long since rejected by anthropologists, and fundamentally misunderstand the nature of ethnography. A properly ethnographic study of cetaceans would directly subvert their positivist methodology and reductionist assumptions.

Commentators expressed a wide variety of views on whether there is a basic capacity limit of 3 to 5 chunks and, among those who believe in it, about why it occurs. In this response, I conclude that the capacity limit is real and that the concept is strengthened by additional evidence offered by a number of commentators. I consider various arguments why the limit occurs and try to organize these arguments into a conceptual framework or “metatheory” of storage capacity limits meant to be useful in future research to settle the issue. I suggest that principles of memory representation determine what parts of the representation will be most prominent but that limits of attention (or of a memory store that includes only items that have been most recently attended) determine the 3- to 5-chunk capacity limit.

The following questions are considered: Why is it difficult to create a theory of consciousness? What are the contents of consciousness? What kind of theory is acceptable as transparent? and, What is the value of conscious experience?

Studies on captive dolphins have shown that they are capable of social learning. However, ethnographic data are less conclusive and many examples given for social learning can be explained in other ways. Before we can claim that cetacean culture is unique we need more rigorous studies which are fortunately not as difficult as Rendell and Whitehead seem to think.

An experimenter studies “sensorimotor contingencies”; the stimulus is primary and the subject's response consequential. But the subject, looking at the world from his or her distinctive viewpoint, is occupied with “motorsensory contingencies”; the response is now primary and the sensory consequential. These two categories are gathered together under the one term in the target article. This commentary disambiguates the confusion.