Fig. 1.

Comparison of articles published until 2000 and from 2001 till 2020 available on GoogleScholar, searched using the keywords “dog cognition”, “dog perception”, or “dog emotion”. The same search using the terms “cat cognition”, “cat perception”, or “cat emotion” was used for comparison purposes in the same periods. The explosion of studies in these areas is particularly evident since the turn of the millennium for dogs: up to the year 2000, GoogleScholar displays only 10 results when searching, for example, for “dog cognition”, but in the next 20 years period (2001–2020) 720 results appear; “dog perception” returns 47 results pre-2000 and 170 studies since, while “dog emotion” returns 7 results pre-2000 and 86 results since. This represents a 72, 3.6, and 12.2 times increase for these research topics in dogs, respectively compared with only 3.4, 1.2, and tenfold increase for cats