What crayfish can teach us about tough decisions

"I'm outta here" - a crayfish performs a tail-flip (Photo: David D. Yager/Jens Herberholz, University of Maryland)

A team from the University of Maryland has studied the decision-making processes of crayfish in an effort to better understand the workings of the human brain.

Crayfish were chosen because they have fewer and more accessible neurons than humans or other “higher” animals. That said, what’s observed with them should more or less apply to us. “Matching individual neurons to the decision making processes in the human brain is simply impractical for now,” explained psychologist Jens Herberholz, the study’s senior author. “History has shown that findings made in the invertebrate nervous systems often translate to more complex organisms. It’s unlikely to be exactly the same, but it can inform our understanding of the human brain, nonetheless. The basic organization of neurons and the underlying neurochemistry are similar, involving serotonin and dopamine, for example.”

In the experiments, crayfish in a tank were simultaneously presented with the scent of food, and the shadow of a perceived predator. They could chose to either flee the area by performing a tail flip, or to freeze in place, in hopes that the predator would pass them by and they could proceed to eat.

Their choice was made in a matter of milliseconds, and could be influenced by manipulating the two stimuli. When the shadow approached rapidly, the crayfish chose to freeze, as the futility of fleeing was outweighed by the possibility of feeding. They also froze when the food scent was made stronger, as the apparent reward in sticking around was more obvious. A strong enough predator stimulus, however, ultimately caused them to tail-flip away.

Essentially, it all came down to a human-style risk/reward analysis.

“Our results indicate that when the respective values of tail-flipping and freezing change, the crayfish adjust their choices accordingly, thus preserving adaptive action selection,” the U. Maryland study concluded. “We have now shown that crayfish, similar to organisms of higher complexity, integrate different sensory stimuli that are present in their environment, and they select a behavioral output according to the current values for each choice.”

The researchers are now attempting to identify the specific cellular and neurochemical mechanisms involved in crayfish decision-making.

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