The psychological assessment of extinct minds

This week, I have published a comprehensive perspective review on cognitive archaeology in the Journal of Comparative Neurology. The article introduces fields bridging prehistory and neuroscience, like paleoneurology and neuroarchaeology. Successively, the relationship between fossils and cognition is discussed following the principles of cognitive archaeology, and the application of psychological models to those behaviors relevant to human evolution. It is important to consider that evolution is based on multiple independent lineages, which make linear, gradual, and progressive changes unlikely. Therefore, the traditional view considering fossil species as “something less” than modern human standards, might be seriously biased. Each species has a distinct combination of mental abilities, and this is probably true also when dealing with extinct taxa and their mind: fossil hominids might have had cognitive skills that we have lost, or never evolved. The cognitive landscape can be, in this sense, influenced by differences in quantity (increasing/decreasing specific skills) and quality (presence/absence of specific skills). In this sense, the simple presence of a specific behavior in the archaeological record is not sufficient to reveal the expression of common cognitive patterns. The frequency of the behavior is crucial, because of the importance of distinguishing occasional vs. habitual responses and adaptations. The complexity of the behavior must also be considered, to avoid generalizations that can hide consistent cognitive changes.

The review then deepens into the fronto-parietal system, working memory, visuospatial cognition, and attention. Following perspectives on embodiment, the importance of the body is discussed in terms of consciousness and self. Haptic, psychomotor, and kinesthetic abilities have mechanical and cognitive aspects, with blurred boundaries with many other broad and narrow skills. At present, we still miss proper conceptual and psychometric tools to investigate their actual roles and influences. Social and technological aspects are also further introduced. Attention, as a cognitive limiting factor, is then particularly discussed, taking into consideration that modern human has a social and technological system that suggests recent evolutionary enhancements in executive, top-down, and focused attentional skills. Many of our cognitive and cultural achievements are probably due to the fact that our attention is intentional, sustained, and conscious.

Finally, the role of the parietal cortex in the narrative of the self is presented. The precuneus, which is much larger in Homo sapiens when compared with other primates and, probably, with extinct hominids, is interpreted as a “beamer” of our storyline, integrating body and visual imaging. The outstanding imaging capacity of our species has, anyway, a drawback: an out-of-control mind wandering through past memories, future expectations, and ruminations, leading to that ontological suffering described by multiple philosophical traditions. If this vulnerability is due to a mismatch between attentional and visual skills, competing for the same neural and cognitive resources, such suffering must be interpreted as a human universal, following the principles of human ethology. Subsequently, I introduce the subsystem model of John Teasdale, employed in Mindfulness-Based Cognitive Therapy (MBCT) and based on two different forms of reasoning: holistic intuitive (based on perception) and conceptual (based on phonological and imaging resources). The former is largely developed on on-line somatic and attentional factors, while the latter is based on off-line information, working memory, and the default network. We can hence wonder whether different hominids might have relied on distinct combinations of the two subsystems.

The review ends with a call for experimental and quantitative methods in cognitive archaeology. Experimental psychology can supply, in this sense, efficient tools and perspectives. Sometimes, experimental approaches are criticized in cognitive archaeology because of the employment of “modern minds” to make experiments, forgetting that, usually, apes are used as models for human evolution, macaques are used as models for the human brain, and mice and worms are used as models for the human medicine. Science works with models. In this case, a human (H. sapiens) is used as a model for other humans. Not that bad! A second common criticisms deal with the fact that theories and hypotheses in archaeology cannot be proven. This is true, as it is for any other field of science. Selection of hypotheses is based on available data, in physics, ecology, or molecular biology. That’s how science works. As a final remark, the review stresses the importance of somatic, social, and technological elements when investigating cognition, in particular when dealing with a human primate.

Attentional mismatch

I have recently participated in a special issue dedicated to the Origins and Development of Attention Networks, with a paper on Cognitive Archeology and the Attentional System. Attention was probably a crucial factor in human evolution, dealing with an array of cognitive abilities that influence (and constrain) the employment of many other broad and narrow cognitive skills. Selection of stimuli is a key issue when dealing with tool use, tool making and tool sensing, as well as for many modern humans’ specific behaviors like teaching and learning, or for many aspects concerning social and technological complexity. Executive attention is, in this sense, particularly relevant too. Executive attention coordinates offline information stored as visual and phonological resources in both the working memory model and in the default mode network. Modern humans (Homo sapiens) display, at the same time, large and complex parietal lobes, and complex visuospatial behaviors, and it may be hence hypothesized that our lineage underwent a specialization of the visuospatial system, involving body cognition, mental imaging, and spatial abilities. When extended to a physical, chronological, social and mnemonic spaces, such cognitive package supports self-narrative, mind wandering, and consciousness, as the egoic projection of our own storyline. I propose that, in our lineage, this specialization might have generated a sort of mismatch between attention and visuospatial skills, in which both processes compete for the same neural resources, with the latter exceeding the capacity of the former. An excess of mind wandering or virtual projection might be actually adaptive, in the sense of improving the reproductive success and the general survival. Nonetheless, at individual level, it is often associated with excessive ruminations, psychological distress and anxiety. Indeed, most philosophical traditions have recognized psychological suffering and existential crisis as a common human trait which, according to the principles of human ethology, must be interpreted as a human universal, independent of cultural factors and hence rooted in our phylogenetic program. At the same time, many different cultures have proposed some form of meditation as a possible individual response to this cognitive constraint, namely a psychological training largely based on somatic and perceptual resources aimed at limiting mind wandering through the activation of the attentional networks. A first paper on this topic was published one year ago in the journal Intelligence. There is also this dissemination article (in Spanish) on attention and cognitive evolution.

The enigmatic stone balls

Shaped stone balls are tools that represent a hallmark of Lower Paleolithic, extending to more recent times, and with a noticeable geographic distribution. These spherical items show signs of intentional shaping, and different definitions and classifications have been proposed according to technological or functional principles. Nonetheless, their function is indeed uncertain. If they are preconceived tools, they could have been used as bolas or throwing stones for hunting animals, or as food-pounding tools. Or, they could be by-products of specific technological processes (exhausted cores, hammerstones, etc.). The spherical geometry and the angled facets, however, have some interesting structural properties, as well as clear ergonomic features. We have now published a perspective review, leaded by Ella Assaf, on these elusive Paleolithic objects. In this article, we present an overview of the archaeological information available to date on these tools, and then discuss both cultural and ergonomic issues, associated with hand-tool perceptual integration. We hope this review can stimulate further the debate on the stone balls and, at the same time, call the attention on the peculiar human ability to integrate objects as “tools” according to both somatic and cognitive mechanisms. Somatic integration requires a large set of haptic abilities (including dynamic touch), and cognitive integration requires a large set of brain-body reciprocal signals. When humans became “obligatory tool-users”, such skills could have seriously influenced their reproductive success and evolutionary fitness, and were hence susceptible of triggering selective responses and biocultural adaptations. Such “prosthetic capacity”, integrating somatic, technological and social factors, could have therefore been a key aspect of modern human evolution. This means that, beyond tool-using and tool-making, cognitive archaeology should be also interested in tool-sensing.

***

Prehistory and neuroscience

Anthropology and neuroscience have always had a strange relationship of “occasional acquaintance”, generally because they are deeply interested in the same target: humans and their brains. Methods and principles of the two fields can be, in turn, rather different, with the former being more holistic and descriptive, and the latter more reductionist and quantitative. In the last two decades, nonetheless, computed and molecular techniques have provided shared tools for both disciplines, and this has prompted a fruitful rapprochement between anthro and neuro people. Prehistory provides, in this sense, a stimulating common ground, because of the joint interest of both fields in human evolution. Paleoneurology, neuroarchaeology and cognitive archaeology are new disciplines born from recent attempts to bridge the human and neural sides of cognitive evolution. Paleoneurology deals with the anatomy of the brain in fossil species, neuroarchaeology with brain functions associated with behaviors inferred from the archaeological record, and cognitive archaeology with psychological models associated with those behaviors. These new disciplines have interesting potentials and crucial limitations, which should be carefully considered when promoting and testing evolutionary scenarios. Importantly, as in most novel fields, a theoretical stage is indeed necessary, but must be properly followed by an experimental one. Otherwise, the discipline will not enter a coherent scientific debate, and its hypotheses would be thus relegated -despite their intrinsic value- to the realm of personal opinions.

Two curious and suspect criticisms frequently raised about these three disciplines deal with 1) the use of modern taxa (generally, living humans) to make inferences on extinct ones, and 2) the fact that many evolutionary hypotheses on cognition can never be proved. I say “curious and suspect” because these limitations are indeed implicit in science and research, whatever the field involved. About the first aspect (a sort of actualism), the use of “models” is a common practice in science. Mice, worms, or sea urchins are commonly used as models for investigating human health and neuron biology. Macaques are a traditional model in human neurobiology, despite they represent only one of >300 species of living primates, and of course not an ancestral missing link of anybody. And, although they belong to a derived living genus profoundly specialized for rain forest, chimps have always been used as model for human evolution. If nobody has any concern in all these cases, why using living humans (Homo) as model for other humans does generate such a crude reaction? After all, until time machines are not available and fMRI can’t be used to explore a Neandertal brain (we, the future aliens abducting past humans! ;-)), there are no alternatives to such inferences. As there are no alternatives in many cases in which mice, flies, macaques or chimps are used instead of human subjects. Leaving these fields to a theoretical stage would mean neglecting their scientific value, and rejecting these fields as a whole would mean denying the use of models in science. Both positions look, indeed, unreasonable.

About the impossibility to verify any hypothesis on past minds, yes, that’s true: those hypotheses can’t be verified. As in any other scientific field. I think Karl Popper did a very good job explaining why a hypothesis can be falsified but never proved. This is true in human evolution, as in physics, molecular biology, or histology. We design hypotheses based on our current knowledge, and then collect observations that, in some cases, discard the hypothesis itself. Accordingly, hypotheses are, little by little, selected and refined, but never proved. The experimental approach is the key to the selection of hypotheses and theories. Hypotheses and theories that can be more or less probable, but never certain. Conclusive firm statements are more suited for religion than for science. Or, for those circumstances in which science becomes a religion.

Within the volume for the centenary of the Journal of Anthropological Sciences, I have now published a review on these new fields bridging prehistory and neuroscience [pdf download], by using, as fil rouge, my own educational and professional career. I hope this review can be useful to introduce some epistemological topics in the current debate, and to give some cues to those students and scholars who are flirting with the possibility to integrate anthropology and neuroscience within an evolutionary perspective.

Tracking knappers

We have just published one more article on eye-tracking and Lower Paleolithic tools. This time, we analyzed the pattern of visual attention during tool-making. In this pilot study (one single knapper) we quantified overt visual attention when knapping choppers and handaxes. There are differences between the two visual strategies, which suggests that there are distinct visuospatial (cognitive) processes involved. The attention is distributed differently when considering the tool regions or the knapped surface. Also, visual attention displays a more homogeneous pattern for handaxes, possibly because of a more standardized procedure, while it is more variably distributed for choppers. In both cases, anyway, the blank is the main element involved (not the hammer or the flake), as well as the next region of percussion (revealing the attentional schemes of planning and prediction). Visuospatial ability can have experienced major changes during human evolution, and the quantification of the behaviors involved in this domain is hence a stimulating issue in cognitive archaeology. Here more posts on eye-tracking and Lower Paleolithic tools.

Tool shape and visual attention

One more study on visual exploration patterns associated with Lower Paleolithic stone tools, this time dealing with the influence of the tool morphology. Previous analyses suggested attentional differences while observing choppers and handaxes, and eye scanning patterns that are independent of the visual saliency of the tool features. According to the results from this new eye-tracking study, however, visual attention is somehow influenced by the general morphology of the tool in handaxes, while for choppers the only correlated factor is their weight. Vision represents the first perceptual interaction between brain, body and tool, and it is hence supposed to be a key factor for triggering the evolution of a human-specific prosthetic capacity. All this is part of a wider research on cognitive archaeology and the evolution of visuospatial functions.

***

And, a few weeks later, here is another one on how experience can influence visual exploration of these stone tools. We measured visual attention while eye-scanning choppers and handaxes in naïve subjects and archaeologists. The pattern of visual exploration is roughly similar, although archaeologists spontaneously devote more attention to the functional part of the tool (i.e., the tool tip) and to the knapped surface, revealing top-down influences. Interestingly, there are no patent differences in the exploration of the tool base, that is the part dedicated to the grasping (prosthetic) interaction.

Visual attention and cognitive archaeology

Investigating the perceptual relationships between body, brain and technology is crucial to understand the peculiar evolution of the human cognitive capacities. In this sense, attention is a key factor and, as primates, visual inputs are our first and more comprehensive sensorial cues to the outer world. After our first paper on eye-tracking and Paleolithic tools, this week we have published a study on visual attention and saliency with images of choppers and handaxes. The study includes one on-line experiment based on remote selection of features, and one eye-tracking experiment based on the detection of pupil behaviour. Images of choppers and handaxes trigger different patterns of visual exploration, in terms of dwell time and fixation counts, partially influenced by morphological dimensions. The knapped surface is more explored than the raw surface, and the tip (the functional region) is more explored than the base (the grasping region). Interestingly, these patterns of visual exploration are not associated with saliency maps, as defined according to the discontinuities in colour, geometry, and texture of the pictures. This study was part of a collaboration with Timothy Hodgson, at the Lincoln University. Here a post from his blog, with a nice video showing eye fixations on stone tools.

Eyes and tools

This week, we present a new research line for the lab, we have been developing in the last couple of years: visual attention and cognitive archaeology. After our previous surveys on haptics and Lower Paleolithic stone tools, we have now begun to investigate how early human technology influences our visual exploration patterns, by using eye-tracking to analyze the schemes of saccades and fixations according to the dwell time and fixation counts. We analyzed the pattern of visual exploration in choppers and handaxes, through vision-only or associated with hand manipulation. The two tool types trigger different visual exploration patterns. In general, the central region of the tool is the more explored one, followed by the tool tip. The knapped region triggers more visual attention than the raw cortex. We found no differences in the visual exploration patterns when the tool is handled, or between males and females. Beyond the central issue of visual attention and cognition, this research line has two main wider targets. The first one is to promote experimental and quantitative approaches in cognitive archaeology, a field that is still largely based on theoretical perspectives but rarely brought into labs and stats. Quantification is mandatory to evaluate theories and hypotheses according to falsification criteria and experimental procedures.  The second aim deals with theories on extended cognition, trying to understand if, how much, and in what way tools are integrative parts of our cognitive system. If humans have evolved a specialized prosthetic capacity, cues of its visuospatial and body integration functions should be still detectable in the changes associated with the paleontological and archaeological record.

Electrodermal hands

After our first research article on stone tool manipulation and electrodermal reaction, here a second one on the effect of hand size and morphology. Females display larger electrodermal variation and higher peaks than males in both arousal and attention, but they also have smaller hands. So, the different electrodermal reaction to tool manipulation could be due to an allometric effect associated with hand size. Accordingly to our results, this is not the case, and these electrophysiological differences during haptic exploration are instead real sex differences, due to biological or cultural factors. By the way, the length and width of the palm are the hand variables with more sexual dimorphism, while the thumb length is the one showing less sexual differences. For a general review on body cognition and cognitive archaeology, you can also see this article on hand-tool interaction, recently published in a  Current Topics in Behavioral Neurosciences volume dedicated to the Processes of Visuospatial Attention and Working Memory.

Paleoneurology at UCCS

At the end of August we will begin a renewed online course in Human Paleoneurology at the Center for Cognitive Archaeology of the University of Colorado Colorado Springs. Here a post introducing the course, and the information on registration and credits.