Dogs with small brains are smarter.
A small brain – and yet a clever mind: Recent research shows why dogs with comparatively tiny brains are often the cleverest strategists.
The smartest dogs are not necessarily those with comparatively large brains. On the contrary, those with relatively small brains compared to the rest of their bodies perform better in some intelligence domains than dogs with relatively large brains – this is the finding of researchers published in the journal “Biology Letters” of the British Royal Society.
According to the study, what matters is not sheer brain volume but how efficiently it is organized. Working dogs, in particular those subject to diverse demands, have relatively small brains but demonstrate high trainability and perform complex cognitive tasks, the research found.
Data from more than 1600 dogs were analyzed.
The team led by Ana M. Balcarcel from the French University of Montpellier analyzed cranial cavity volume and behavioral data from 1682 dogs across 172 breeds. Using the brain volume within the skull, the researchers determined the relative brain size, i.e., the ratio of brain size to body size.
The scientists linked these measurements to the traditional working tasks of the breeds, their body size, head shape, and standardized data on breed-specific behavior. This allowed them to examine whether certain functional groups – such as working dogs, hunting dogs, or companion dogs – differ systematically in their brain architecture and temperament.
Small brains, big performance
The surprising finding: Working dogs like huskies, Rottweilers, or Pyrenean Mountain Dogs, bred for complex assistance tasks and considered particularly intelligent, have the smallest brains relative to their body size. At the same time, these breeds are found in tests to be very trainable, with good behavioral control and better short-term memory abilities considered part of higher cognition.
The authors interpret this to mean that the “smarter” dogs use their neural tissue particularly efficiently: their brains are, in a sense, compactly packed within the skull, without any loss of performance. Unlike in wild mammals, where relatively larger brains are often associated with more complex cognition, this simple rule does not seem to apply to domestic dogs.
Large brains, more sensitive dogs
Toy breeds like Chihuahuas, Pomeranians, or Yorkshire Terriers, on the other hand, have the largest brains relative to their body mass. These small dogs have been bred primarily as companion and lap dogs for generations – closeness to humans and a desire for attention were desirable traits.
However, behavioral data reveal that breeds with large relative brain size are more prone to fear and aggression, more frequently exhibit separation anxiety and pronounced attention-seeking, and, on average, are less trainable. Relative brain size increased with fear, aggression, and clinginess in the analysis, and decreased with increasing trainability.
The study suggests that complex cooperative abilities—such as accurately following signals, flexibly solving problems, or reliably controlling impulses—are not linked to a large relative brain volume. Rather, the brain’s internal wiring, such as the development of the cerebral cortex in large dogs, may be more important than the ratio of brain to body weight.