Why trying it alone often falls short
A young animal that never watched a skilled adult would have to discover a working tool technique from scratch. That is possible, but it is a slow and unreliable way to arrive at a precise sequence of movements. The chimpanzee study is instructive here: by mapping which individuals acquired a novel tool-use variant and when, relative to their social connections, the researchers could show that acquisition followed the animals' network ties rather than appearing independently across the group [3]. That pattern is hard to produce by individual learning alone.
The capuchin work points in the same direction but adds a twist. Tool use in that population seems to be acquired by social learning, and the spread is not random: social tolerance and a tendency to copy successful individuals appear to shape the transmission [4]. In other words, it is not just that animals learn from others, but that they learn selectively from the ones who are doing well. That kind of selectivity is difficult to explain as pure trial and error.
Where individual learning carries more of the load
The case for individual learning is strongest when you look across many species rather than one group. A review of tool-use forms across species makes the point that individual learning has been undercredited, and that many tool-use behaviours can arise without copying [2]. Even so, the same review reports that a conservative estimate of social transmission accounted for 85% of observed cases, which means that even a sceptical accounting leaves social transmission as the majority explanation [2]. The two claims sit together: individual learning matters, but it is usually not the whole story.
New Caledonian crows offer a useful illustration of how the routes can be tangled. In hand-raised birds, the development of twig tool use was observed in order to separate inherited action patterns, individual learning, and social transmission [5]. The very design of that study reflects the difficulty of the question: when a bird produces a competent tool behaviour, it is not obvious whether the behaviour came from an inborn motor pattern, from practice, or from watching others. The study treats all three as live possibilities rather than assuming one.
So how much can individual learning explain?
Putting the evidence together, individual learning looks like a genuine and sometimes sufficient route to tool use, but the studies that track spread through groups tend to find social transmission doing substantial work. In macaques, work on tool-use acquisition explicitly examines both individual learning and social transmission, including how observing skilled models influences learning and how monkeys generalize and adapt their motor strategies [1]. That framing is itself informative: the question is not usually which mechanism operates, but how the two combine.
The balance also depends on what is being measured. A study that watches a behaviour appear in a group can detect social transmission through the timing and network pattern of acquisition [3], while a review that catalogues tool-use forms across species can count how many behaviours plausibly require copying [2]. These are different lenses, and they can give different impressions of how much individual learning is doing. What the evidence does not support is the idea that individual learning alone accounts for animal tool use in general; the group-level studies keep finding signatures of transmission that independent discovery would not produce [3][4].
Sources used in this answer
Individual and social learning processes involved in the acquisition and generalization of tool use in macaques
Macaque tool-use acquisition involves both individual learning and social transmission, including the influence of observing skilled models and the ability to generalize and adapt motor strategies.
Exploring the role of individual learning in animal tool-use
A cross-species review argues individual learning of tool use has been undercredited, yet a conservative estimate of social transmission still accounted for 85% of observed cases.
Social network analysis shows direct evidence for social transmission of tool use in wild chimpanzees
Social network analysis in wild chimpanzees provides direct evidence that two novel tool-use variants spread through social transmission rather than independent individual learning.
Social tolerance and success-biased social learning underlie the cultural transmission of an induced extractive foraging tradition in a wild tool-using primate
In wild capuchins, tool use appears to be acquired by social learning, with social tolerance and success-biased copying underlying the transmission.
Development of tool use in New Caledonian crows: inherited action patterns and social influences
Observing hand-raised New Caledonian crows showed that twig tool use develops through a mix of inherited action patterns, individual learning, and social influences.