{"fact":"Studies on crows' cognitive abilities often use string-pulling tasks, but these seemingly simple tasks can reveal complex problem-solving strategies.","context":"To estimate the abilities of passerine birds to comprehend cause–effect relationships, two species of corvidae family (common ravens and hooded crows) and two species of small passerine birds...were subjected to a battery of tasks with different spatial relationships between the strings and baits.","source":"Z. A. Zorina; T. A. Obozova, New data on the brain and cognitive abilities of birds, 10.1134/s1062359012070126","index":347}