Pigeons are not so clever after all.
New research at the University of Iowa shows that pigeons can discriminate abstract concepts of space and time– and seem to use a different region of the brain than humans and primates to do so. In the experiments, the pigeons were shown on a computer screen with a static horizontal line and had to judge their length or the amount of time that was visible to them. The pigeons judged that the longer lines also had a longer duration and considered that the longer lines were also longer.
What it means, says Edward Wbaderman, Stuit Professor of Experimental Psychology in the Department of Psychological and Brain Sciences at the UI, is that pigeons use a common area of the brain to judge space and time, suggesting that these abstract concepts are not processed separately. Similar results have been found with humans and other primates.
The finding adds to the growing recognition in the scientific community that lower-order animal species, such as birds, reptiles and fish, are capable of high level, summary decision-making.
"In fact, the cognitive skills of birds are now considered increasingly closer to that of human and non-human primates," says Wbaderman, who has studied intelligence in pigeons, crows, baboons and other animals for more than four decades "Those avian nervous systems are capable of much greater achievements than the pejorative term" bird brain "would suggest."
Humans are capable of perceiving space and time, even without the aid of inventions such as a clock or a rule. The region of the brain that helps humans make those more tangible abstract concepts is the parietal cortex, part of the cerebral cortex and the outermost layer of the brain. It is known that the cerebral cortex is a place of higher thought processes, including speech and decision making, and the four lobes that make it up, including the parietal cortex, process different types of sensory information.
But the brain of pigeons does not have a parietal cortex, or at least one developed enough to be different. Then, birds must use another area of the brain to discriminate between space and time, or there may be a common evolutionary mechanism in the central nervous system shared by primates and primitive birds.
Wbaderman and his team wanted to discover it.
They put the pigeons through a series of tasks called the "common magnitude" test. In short, the birds are displayed on a computer screen with a horizontal line of 6 cm or 24 cm long for 2 seconds or 8 seconds. If they correctly reported (by pecking one of the four visual symbols) the length or duration of the line, they received food.
The test became more nuanced. The researchers introduced additional line lengths, thus adding greater variability in judging whether a line was short or long; They also presented the line to the pigeons for a shorter or longer duration.
"The task now forces the pigeons to process time and space simultaneously because they can not know in which dimension they are going to be tested," says Wbaderman.
The researchers found that the length of the line affected the discrimination of the pigeons for the duration of the line, and the length of the line affected the discrimination of the line length of the pigeons. This interaction of space and time was parallel to the research conducted with humans and monkeys and revealed the common neuronal coding of these two physical dimensions. The researchers previously believed that the parietal cortex was the site of this interaction. However, because pigeons lack an apparent parietal cortex, Wbaderman's findings suggest that this is not always the case.
The article "Coding of the non-cortical magnitude of space and time by pigeons" was published online on December 4 in the journal Current Biology .
Benjamin De Corte, a third-year graduate student at the Iowa Neuroscience Institute of the UI and Department of Neurology who helped design and execute the experiments, says the results show that pigeons process space and time ways similar to those of humans and other primates.
"The cortex is not unique in judging space and time," says De Corte, who is the first author of the article. "Pigeons have other brain systems that allow them to perceive these dimensions."
Víctor Navarro, a UI graduate student in the Wbaderman laboratory, helped design and carry out the experiments and is a contributing author in the article.
The Alfred P. Sloan Foundation funded the research.
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