Based on a joint study between Dr. Spencer Behmer, a Texas A&M University assistant professor of entomology, and researchers at the University of Oxford, the United Kingdom, the grasshopper would likely have developed this preference based on its physical state at the time – its reserves were low, and it was hungry.
"When you’re deprived, things taste better, and their perceived value may be exaggerated," said Behmer, who has a joint appointment with the Texas Agricultural Experiment Station.
Behmer studied the phenomena of ‘state-dependent learned valuation’ in a grasshopper, the African desert locust, Schistocerca gregaria, at the University of Oxford before moving to Texas A&M in August. He collaborated with Dr. Lorena Pompilio, who was then a graduate student, and Dr. Alex Kacelnik, her major adviser. Their study was published in Science on March 17.
"This work suggests that researchers may need to pay more attention to the state of the subject – whether vertebrate or invertebrate – at the time of learning," Behmer said.
"African desert locusts were used because they are known to be good learners, which may be important as they are extreme generalists when it comes to their diet – they eat just about any kind of plant," Behmer said. "Learning allows them to make quick decisions about whether they should eat a particular plant."
During the study, locusts were trained under one of two conditions – hungry or well-fed – for separate parts of the day (morning or afternoon). In each state, they were repeatedly given a small piece of wheat, and at the same time, exposed to an odor, either peppermint or lemon grass.
Training lasted for three days, and the size and quality of the wheat presented was identical in both conditions. On the fourth day, half of the locusts were starved and half were well fed, and then each was exposed to the odors once again in a ‘Y maze.’
Results showed that the locusts nearly always chose the arm of the Y-maze containing the odor that they experienced while in the deprived state. Interestingly, the well-fed locusts also preferred the odor previously associated with the deprived state.
"The absolute size of the rewards were identical in both states," Behmer said. "There should have been no preference."
"The sensitivity of the taste receptors on the locusts’ palps (finger-like projections near the mouth) change according to the internal state of the animal," he said. "The hairs on the palps, which are similar to a human tongue, enable the locust to taste its food, and if the locust is deprived of a nutrient, these hairs tend to be more easily stimulated when the missing nutrient is eventually encountered. The strong signal from these hairs pairs with a signal from the smell."
"The locust forms an association between the two and a signal is then sent to the brain, where it gets processed," he said. "It seems locusts assign greater value to the wheat experienced during the deprived state, and this is why they prefer the odor associated with the deprived state even though no preference should exist."
A link between preferences and physical state had been made in previous studies of vertebrates – humans and birds. But this link had never been studied in invertebrates.
Behmer said an intrinsic cognitive process doesn’t seem to be involved in decision-making in locusts, whose brains are tiny compared to humans. They contain an estimated 360,000 neurons. The human brain contains 100 billion neurons.
He plans to continue studying learning mechanisms at Texas A&M, using Schistocerca americana, a grasshopper native to Texas.
Dr. Spencer Behmer | EurekAlert!
Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University
New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy