At this point you might be asking: "What's with the horrible pun in the title?". The answer is found when we compare the novel aspect of Saxe's work with the novel aspect of the recent work of Taylor, Miller and Gray. The former is interesting for extending evidence of causal reasoning to very young children, and the latter is interesting for extending evidence of causal reasoning to crows.
In their latest paper, "New Caledonian crows reason about hidden causal agents"2, Taylor and colleagues set up an analogue situation to that used by Saxe that was obviously adapted for crows (or perhaps they just could not find any puppets and toys trains at short notice). Their design is best characterised in the figure below:
The logic behind the experiment is that the crow should hesitate when attempting to retrieve their food from the baited tube, as movement of the stick could result in them being poked in the side of the head (importantly, as the authors take effort to note, this was in actuality impossible as they only moved the stick when setting up the condition, before the crow began to forage for food). In the HCA condition, if the crow accurately infers the association between the movement of the stick and the human, then there should be little-to-no hesitation when foraging for food because the agent causing the movement of the stick leaves before the crow enters the baited tube. In other words, there is no reason to fear being poked in the side of the head. With the UCA condition, however, the crow has no clues about what could be causing the movement of the stick so it has no information on whether the stick will move again or not (thus presenting a risk). The results are shown below:
The pretty lines and dots tell us that in the HCA condition, the crows spent significantly less time investigating the stick and surrounding before foraging for food. Since the only difference in the two conditions was the observation of a second experimenter entering and then leaving the hide, our explanation must utilise this variable. The authors argue (and successfully, in my opinion) that the best explanation for this behavior is one that is consistent with the Saxe research - that the crows are demonstrating causal reasoning as they have less reason to fear being poked in the head due to the fact that the agent believed to be causing the movement of the stick is no longer present.
It is pretty amazing research as even though some observational reports had alluded to these possible abilities in animals (for example, Darwin's example of dogs barking at a parasol being blown across a garden by the wind), this is the first example of it being demonstrated in experimental conditions. The authors rightly speculate that the methodology they used could be applied to other animals to assess the causal reasoning abilities of various species, and this could give us some information about possible selective pressures producing this ability.
For anyone interested, the lead author Alex Taylor did an "AMA" (Ask Me Anything) on Reddit yesterday and answered a number of questions put to him on the study. You can find it here: Caws and Effect – IAM Alex Taylor, Evolutionary Psychologist and lead researcher on the recent paper, "New Caledonian crows reason about hidden causal agents". AMA.
1. Saxe, R., Tzelnic, T., Carey, S. (2007) Knowing who dunnit: Infants identify the causalagent in an unseen causal interaction. Developmental Psychology, 43:149–158.↩
2. Taylor, A.H., Miller, R., Gray, R.D. (2012) New Caledonian crows reason about hidden causal agents. Proceedings of the Academy of Sciences, Published Online First: 17 September.↩