The human face as an evolved signaling system
Human faces convey information about identity, age, sex, health, fertility, etc. and movements of the face operate as complex social signals. We are running a number of projects investigating peoples sensitivity to these signals.
Projects currently underway are investigating non-verbal dynamic signaling in a variety of social contexts - the way people's facial movements communicate a wealth of subtle information to their social partners - as well as the brain mechanisms underlying such signaling, the evolution of attractiveness cues, and what they indicate about the owner of the face, and the possible uniqueness of human faces as signallers - do humans have specifically evolved mechanisms to process only human faces, or does this processing extend to other kinds of faces, or to bodies, etc?
We are also interested in the role of movement in conveying many of these signals - to what extent, for example, does facial movement help in recognising individuals?
The evolution of spatial cognitive mechanisms
There is now a well established link between the ecology of a species and its performance on spatial tasks (although there is still some skepticism). For example, when a nectar-feeding bird visits a particular flower they usually empty it of nectar, so it is a bad place to go back to - at least until it has had time to refill. Consistent with this natural fluctuation, we have discovered that the tendency to avoid or return to previously rewarding locations is influenced by the amount of time between visits in Regent honeyeaters, despite the fact that the birds we used had never been exposed to natural flower replenishment rates. Similarly, we have found that Noisy miners, which feed on both nectar and insects, also have a strong tendency to avoid a recently rewarding location - but only if the reward is nectar.
Similarly, can we understand the kind of spatial information humans are good and/or bad at using in terms of human evolutionary history? Has this resulted in males and females having slightly different spatial propensities? We have collected some data which is at least consistent with the idea that human males and females might have brains that are adapted to process different kinds of spatial information, as a consequence of specialising on either hunting or gathering in our evolutionary past.
The evolution of visual sensitivities
This project is investigating how the visual environment a particular species inhabits (its visual ecology) determines its visual sensitivities, via shaping its neural apparatus. Consider, for example, how different the available information in the visual world of a bird is, given that it can easily gain a wide range of perspectives on a scene unavailable to a land-based perceiver like a human. Or consider the problem faced by a marine mammal, which evolved from a land-based animal (and so had a visual system adapted to terrestrial regularities), but which now must deal with a visual world in which many of those regularities no longer apply - under water you can't rely on objects having predictable viewpoints or velocities determined by their own locomotion, for example.
One such study is examining the way in which Jacky lizards (Amphibolurus muricatus) process visual motion information. Do they have particular sensitivity to stimuli that are of biological significance to them (like the movements in male aggressive signals, or movements of their prey), and if so, how? Has communicative signalling in Jacky lizards capitalised on existing perceptual sensitivities, or has the signalling provided selection pressure to evolve new sensitivities?
We are also applying this logic to human vision - what can we understand about how people see the world (including illusions they fall for) by asking what a particular kind of visual sensitivity is actually for?