New Caledonian crows plan for specific future tool use

Abstract

The ability to plan for future events is one of the defining features of human intelligence. Whether non-human animals can plan for specific future situations remains contentious: despite a sustained research effort over the last two decades, there is still no consensus on this question. Here, we show that New Caledonian crows can use tools to plan for specific future events. Crows learned a temporal sequence where they were (a) shown a baited apparatus, (b) 5 min later given a choice of five objects and (c) 10 min later given access to the apparatus. At test, these crows were presented with one of two tool-apparatus combinations. For each combination, the crows chose the right tool for the right future task, while ignoring previously useful tools and a low-value food item. This study establishes that planning for specific future tool use can evolve via convergent evolution, given that corvids and humans shared a common ancestor over 300 million years ago, and offers a route to mapping the planning capacities of animals.

Keywords: New Caledonian crows; comparative cognition; future reward; planning; spoon test.

Figure 1.

The three apparatuses used in the study: (a) dispenser apparatus, (b) platform apparatus, (c) tube apparatus. (d) The tool presentation box, including a stick, stone and hook as tools, apple as a lower-quality food reward and a ball as a distractor object. The ball as a distractor was introduced one day before the first presentation of the five-choice tool functionality training. (Online version in colour.)

Figure 2.

Compartment set-up. (a) The test compartments. The left compartment contains a table, on which the tool presentation box was placed in the choice phase. The right compartment contains a small table where the apparatus was placed at inspection phase and accession phase. Crows could move between compartments when a sliding door was opened. Condition 1: crows observe a tube baited with meat (C1₁) for 1 min, after which they are moved to the left compartment. After 5 min, they are presented with the three tools, a distractor and low value apple (C1₂). Once a choice has been made the tool presentation box is removed. After 10 min the door to the right compartment is opened, allowing the crows to access the food if they have chosen the stick (C1₃). Condition 2: crows observe that the tube is baited with low value apple (C2₁), and then are presented with the choice of three tools, a distractor and meat (C2₂). Once a choice is made the presentation box is removed, and after 10 min the crows are allowed access to the apparatus (C2₃). Conditions 3 and 4: test conditions. Crows are given alternating trials of C3_1–3 and C4_1–3, where they see the platform apparatus (C3₁) or the dispenser apparatus (C4₁) baited with food, and then are moved to the next door compartment, where, 5 min later, they are presented with the tool presentation box containing three tools, a distractor and low value apple (C3₂ and C4₂). To gain the meat the crows need to choose a stone in C3₂ and the hook in C4₂, so they can take this tool to the apparatus in the next door compartment 10 min later (C3₃ and C4₃). We trained the birds in C1 and C2 to understand that the specific future event will differ from the next one and that they have to be attentive to the presented apparatus. This is one of the critiques of the study by Kabadayi & Osvath [8]. Thus, the actual test is when birds have ‘learnt’ the temporal rule and then in the test phase are presented with new apparatus–tool combinations they have to plan for. (Online version in colour.)