One of Coombs and Trestman’s central premises is that “cognition is embodied,” citing Clark (Reference Clark1999). But much has happened in the embodied cognition literature since 1999. The target article could therefore benefit from more interaction with embodied cognition and its offshoots, the most relevant being ecological psychology (Gibson, 1979/Reference Gibson2015; Warren & Fajen, Reference Warren, Fajen, Vaina, Beardsley and Rushton2004), basal cognition (Lyon, Reference Lyon2006; Lyon et al., Reference Lyon, Keijzer, Arendt and Levin2021), and embodied cognitive neuroscience (Anderson, Reference Anderson2014; Cisek & Kalaska, Reference Cisek and Kalaska2010; Pessoa, Reference Pessoa2022). Here, we suggest three ways in which a greater engagement with these areas of the literature can help support, nuance, and contextualize the findings of the target article.

First, the primacy of active perception has long been highlighted in ecological psychology (Gibson, 1979/Reference Gibson2015; Warren & Fajen, Reference Warren, Fajen, Vaina, Beardsley and Rushton2004) as well as in embodied cognition more generally (Engel et al., Reference Engel, Maye, Kurthen and König2013). In line with this, the target article stresses the explanatory centrality of active sensing and visuomotor control: many pivotal traits “can be united in terms of their involvement in active sensing” (p. 8). However, the authors seem to only consider the relevance of active sensing to organisms at complexity level 3 and higher (see their Figure 5). While it is convincingly shown that pivotal traits (such as high-resolution eyes, compensatory eye movements, and laminated visual structures) co-occur in complex creatures because of their involvement in active visual sensing, one of the more recent findings of embodied cognition is that active sensing is operative more widely, such as for example in single-celled eukaryotes (Wan & Jékely, Reference Wan and Jékely2021).

Moreover, ecological approaches suggest that once the organism is actively moving in the right way, perception is relatively easy. A fly does not need to calculate its landing spot, but it can see where it is heading in the optic flow. It can guide its movement by keeping certain perceptual invariants constant. This suggests that the main difficulty lies not in the sensory part of active sensing – as is the focus of the target article, with its emphasis on high-resolution eyes and visual processing – but in the action part: pivotal traits like mobile eyes serve to both uncover perceptual invariants and let behavior be guided by those perceptual invariants.

Second, embodied cognition provides a valuable additional perspective on the origin of trait-linkages. The authors’ framework proposes that certain body, sensory, brain, and motor traits become linked over time (the trait-linkage hypothesis), thereby giving rise to different levels of behavioral and cognitive complexity across lineages. This framework helps to systematize our knowledge of how complex behavior and cognition first arose in different animal lineages. However, in doing so, it adopts a strong present-to-past approach. It takes modern animals to provide the relevant criteria for understanding even very early stages of animal evolution. On this account, animal evolution is cast as a teleological “main road” toward cognitively complex status where some lineages took a wrong turn on one of various “off-ramps” (Figure 9 in the target article).

In contrast, focusing on basal cognition (Lyon et al., Reference Lyon, Keijzer, Arendt and Levin2021) can add a complementary past-to-present perspective wherein the adaptive functionality of early animals is also addressed. This sort of analysis does not start with striated muscle and neurons but goes at least back to when the separate cells of choanoflagellate ancestors first stuck together and eventually became an integrated multicellular organization. Later, in some lineages, these became animal bodies with a gut, muscles, nervous system, physiology and much more, all of which involved sets of coordinated processes that together brought increasingly complex organisms into being (Arendt, Reference Arendt2021; Arnellos & Keijzer, Reference Arnellos and Keijzer2019; Jékely, Reference Jékely2021; Jékely, Keijzer, & Godfrey-Smith, Reference Jékely, Keijzer and Godfrey-Smith2015; Moroz, Romanova, & Kohn, Reference Moroz, Romanova and Kohn2021; Ros-Roscher & Brunet, Reference Ros-Rocher and Brunet2023). Combining the knowledge from these studies on early animal evolution and development with the article’s findings about the distribution of animal traits across lineages can therefore provide a more comprehensive understanding of the evolution of animals, their cognition, and their behavior. This unified perspective will also enable a more focused and detailed approach to understanding how various trait linkages came into being.

Third, embodied cognition provides a candidate evolutionary principle – namely, the neural reuse hypothesis – that can help explain the article’s observation of trait linkages. Anderson (Reference Anderson2010) has described the general tendency of existing neural structures to become co-opted into new functional circuits that are established when an organism learns to solve a novel task or moves into an unfamiliar environment. On the evolutionary scale, such neural reuse suggests that when evolutionary pressures lead to phenotypic changes, the organism’s extant neural resources are “reused and redeployed” (Anderson, Reference Anderson2014) in service of these changes. This view is supported by both mathematical analyses of functional and effective connectivity in mammalian brains (Pessoa, Reference Pessoa2022) and comparative biology studies of a variety of closely related species. For instance, the strong interconnectivity between the superior temporal lobe and the inferior frontal gyrus originally evolved in Old World monkeys due to evolutionary pressures to transmit information about different types of environmental threats via different vocalizations (Deacon, Reference Deacon1997). Sometime during the evolution of Hominidae, this structural connectivity was co-opted into functional circuits capable of producing a series of vocalizations which are interpreted differently within a given social group depending on their syntax (Arbib & Bota, Reference Arbib and Bota2003; Leroux & Townsend, Reference Leroux and Townsend2020). The same principle of co-option is also evident in the development of mathematical cognition based on existent neural structures in the motor cortex (Bruineberg & van den Herik, Reference Bruineberg and Van Den Herik2021; Penner-Wilger & Anderson, Reference Penner-Wilger and Anderson2013). This reuse of neural structures for the development of new cognitive capacities can therefore help explain the linkage of neural and bodily traits suggested by the authors.

To conclude, we have presented three interrelated ways in which concepts and principles from the contemporary embodied cognition literature can be usefully applied to support further development of the multi-trait framework. A deeper engagement with this literature will no doubt reveal more of these conceptual synergies and help to establish a fruitful exchange between the frameworks. In return, the multitrait framework provides strong evidential support for many areas of the embodiment research program and a helpful resource for its practitioners.