When taking a closer look at miniaturized brains, one can see that to carry out complex cognitive processes it is not important to have "big brains": the volume, indeed, tends to be irrelevant. To achieve this, instead of listing disarming species-specific traits that show cognitive capacities well beyond those of humans, I will rather discuss traits that seem to be uniquely human and can be carried out even by little brains. For example, does it require a complex cognitive system to be able to discriminate between different painters and artistic currents? Part of a study conducted in 2013 involved bees that were trained to discriminate between 5 pairs of paintings by Monet and Picasso. The paintings were presented in a way that, in each pair, contrast and color were approximately similar. After training, these bees were not only able to recognize the two painters’ works, but were also able to abstract the perceptual regularities and constancies of the two painters, and used them with remarkable precision in new pairs of paintings they had never seen before (Wu et al., 2012). It has also been shown that Polistes fuscatus wasps discriminate with greater detail the faces of their peers than any other type of stimulus, a feature that is identical to all anthropomorphic apes (Sheehan & Tibbetts, 2011). This is a great example of evolutionary convergence between diametrically different brains, boasting a 100000:1 ratio in their number of neurons. These wasps recognize themselves and are constantly aware of which position each individual occupies on the hierarchy of the nests. 

Furthermore, pigeons show comparable performance to monkeys and humans in orthographic processing  (Scarf et al., 2016) and there is evidence that they showed self-recognition behavior in the mirror test (Epstei et al., 1981). Pigeons’ performance is also remarkable in the experimental task of sample comparison (Vallortigara, 2000), which shows that they can experience abstract concepts such as two things being "equal" and “different". In said task, the animal first sees a stimulus, say a red square, and then has to choose, by moving towards a direction, between a stimulus identical to the one just seen and a new stimulus (blue square). It is important to understand that these animals have learned the rule "pick the equal", because the rule is abstract and applies to any pair of stimuli. 

But how can insects and birds perform like humans? The higher the density of neurons, the shorter the average distance between two neurons in the brain. Therefore, if populations of cells during cognitive tasks need to communicate with each other quickly, they may be able to do so faster in the bees’ brains. Small brains, in terms of number of neurons, can still perform. 

In this welter of cognitive components and abilities, we take a step back to the original issue: No device can measure consciousness, and listing potential capacities does not provide enough factual information to demonstrate that any species is genuinely conscious, but only how much the density or number of neurons do not directly interconnect with the cognitive "abilities" of a given species.