A bigger brain doesn’t always account for a smarter or more intelligent person, says a new study.

The researchers acknowledge that the belief ‘bigger brain means smarter person’ is considered true in general and carries on even among many scientists, but their findings reveal increasingly common exceptions to the rule.

For instance, most biologists presume that bigger-brained rats are way smarter or more intelligent than mice, but scientists at Cold Spring Harbor Laboratory (CSHL) are now challenging this principle.

There was skepticism, however.

"Mice have the potential to greatly accelerate our research. We didn't want to discount a very powerful option based on anecdotal evidence of their inferiority," says Anthony Zador, professor at CSHL, in a statement.

The scientists conducted a systematic comparison of how mice and rats learn performing auditory task that are moderately challenging. They discovered very similar intelligence and performance levels, which could indicate powerful implications to researchers who are examining complex learning and behaviors.

"This was a task that tested perceptual ability as well as adaptability, and we were very surprised to see that mice and rats performed about the same," explains Santiago Jaramillo, Ph.D., who is part of the study. He is previously a postdoctoral researcher at Zador laboratory and now leads his own laboratory within University of Oregon.

Their research revealed one disparity: rats learned rather faster than mice. The training protocol was created and enhanced particularly for rats, which might explain for the minor advantage, according to Jaramillo and Zador.

Yet the discovery of approximately equal intelligence indicates wide implications in terms of cognition research, study says.

"We've found that mice, and all the genetic tools available in them, can be used to study the neural mechanisms underlying decision-making, and they might be suitable for other cognitive tasks as well," Zador says.

Rats have become “rodents of choice” for scientific research on how brain comes up with its decisions and are subjects of extensive protocols in the study of cognitive function, the study says. They are also said to be inexpensive for scientists to keep.

The past few years, however, saw a rise in the quantity of genetic tools accessible to examine mice, described as smaller cousins of rats. The genetic tools help scientists switch genes on and off within the particular neuron population, which is crucial in understanding the method by which complex behaviors develop. Study says several investigators have refrained from making use of these new genetic tools, with the belief that mice aren’t as smart or intelligent as rats.

The study, Mice and rats achieve similar levels of performance in an adaptive decision-making task, was published by Frontiers in Systems Neuroscience journal.