A comparative assessment of birds’ ability to solve string-pulling tasks

Abstract

A set of string pulling tasks was used to compare the cognitive abilities of birds with different levels of brain complexity, which was judged using Portmann's index for the hemispheres. Varying the number and relative position of strings and bait, we investigated whether birds of different species (hooded crows (Corvus cornix), red crossbills (Loxia curvirostra), Eurasian blue tits (Parus caeruleus), and great gray owls (Strix neb ulosa)) are capable of comprehending the logical structure of such tasks based on cause-effect relationships. Among the observed representatives of Passeriformes, only hooded crows, which possess the most complex and highly differentiated brain, were shown to be able to solve correctly the most difficult versions of the string pulling tasks and, therefore, to understand their logical structure. Small passerine birds and owls, which are characterized by a similarly high value of Portmann's index, proved to be incapable of compre hending the cause-effect relationship between the components of the tasks.

The ability of oriental magpies (Pica serica) to solve baited multiple-string problems

“…3), of which only P5 solved the parallel task (T1 ; Table 2), and P6 solved one of the two tasks of slanted strings (T3) without learning. Part of our results were similar to those from reports on western scrub-jay (Aphelocoma californica) (Hofmann, Cheke & Clayton, 2016), the common raven (Coravus corax), and the hooded crow (C. cornix) (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014). The number of tests conducted by different researchers was different.…”

“…3; Table 2) or the cross string task (T5; Fig. 3) as the common raven could, and the task of continuity and discontinuity (T7) as hooded crow did (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014). The eight magpies in this study solved fewer multiple-string tasks than the Corvus birds (only three out of eight magpies solved a few multiple-string problems) despite their close evolutionary relationship (Ericson et al, 2005).…”

“…There were individuals in raven (one of four), hooded crow (two of four), and western scrub-jay (one of five) solving the task like T2 of this study, whereas all magpies of this study could not solve T2 and two magpies (P5 and P8) showed significant proximity principle. Our magpie was similar to the hooded crow, they couldn't solve the cross string (T5) and showed significant proximity principle (two of eight in two researches respectively), and there was also one magpie (P6) showing a significant proximity principle (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014). The hooded crow could solve both tasks like our T6 (four of the eight crows) and T7 (continuity strings; six of eight crows), but only one of our magpies (P1) could solve the task of turning (T6) through trial and error learning, and all of them couldn't solve the task of continuity strings (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014).…”

“…Our magpie was similar to the hooded crow, they couldn't solve the cross string (T5) and showed significant proximity principle (two of eight in two researches respectively), and there was also one magpie (P6) showing a significant proximity principle (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014). The hooded crow could solve both tasks like our T6 (four of the eight crows) and T7 (continuity strings; six of eight crows), but only one of our magpies (P1) could solve the task of turning (T6) through trial and error learning, and all of them couldn't solve the task of continuity strings (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014). In a task like our T6, one hooded crows showed significantly proximity principle, but we did not find our magpies used proximity principle to solve the task of turning strings (Bagotskaya, Smirnova & Zorina, 2012).…”

“…The number of tests conducted by different researchers was different. For examples, the raven and western scrub-jay were tested 32 and 50 times in each of their tasks, respectively, and the hooded crow 30-32 times in tasks of one report and 20 times in tasks of another (Bagotskaya, Smirnova & Zorina, 2012;Obozova et al, 2014;Hofmann, Cheke & Clayton, 2016). So we only compared the binomial test results of our magpie and other birds in the family Corvidae who also performed horizontal string-pulling tasks.…”