Historians of science have pointed to essentialist beliefs about species as major impediments to the discovery of natural selection. The present study investigated whether such beliefs are impediments to learning this concept as well. Participants (43 children aged 4-9 and 34 adults) were asked to judge the variability of various behavioral and…

Dramatic biodiversity changes occurring globally from species loss and invasion have altered native food webs and ecosystem processes. My research objectives are to understand the consequences of fish diversity to freshwater systems by (1) examining the food web consequences of multiple top predators, (2) determining how biodiversity influences…

Intercellular signaling is vital to communication within neuronal circuits. The suprachiasmatic nucleus (SCN), the master circadian clock of mammals, contains a dense collection of neurons that align their intrinsic rhythmicity with environmental stimulus and physiological state. While peptide physiology has been demonstrated as a contributor to…

Aged mice exhibit a heightened central inflammatory cytokine response, as well as prolonged hippocampal-dependent cognitive deficits, compared to adults when administered lipopolysaccharide (LPS) to mimic a peripheral infection. The excessive production of inflammatory cytokines such as interleukin (IL)-1[beta] within the brain is proposed to…

Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

This experiment examined the relationship between reinforcer magnitude and quantitative measures of performance on progressive-ratio schedules. Fifteen rats were trained under a progressive-ratio schedule in seven phases of the experiment in which the volume of a 0.6-M sucrose solution reinforcer was varied within the range 6-300 microliters.…

Many drugs of abuse produce changes in impulsive choice, that is, choice for a smaller-sooner reinforcer over a larger-later reinforcer. Because the alternatives differ in both delay and amount, it is not clear whether these drug effects are due to the differences in reinforcer delay or amount. To isolate the effects of delay, we used a titrating…

The control exerted by a stimulus associated with an extinction component (S-) on observing responses was determined as a function of its temporal relation with the onset of the reinforcement component (S+). Lever pressing by rats was reinforced on a mixed random-interval extinction schedule. Each press on a second lever produced stimuli…

Concurrent schedules were used to establish 6 hens' preferences for three foods. The resulting biases suggested wheat was preferred over honey-puffed and puffed wheat, and puffed wheat was the least preferred food. The hens then responded under fixed-ratio schedules for each food in 40-min (excluding reinforcer time) sessions, with the response…

According to the composite-stimulus control model (Weiss, 1969, 1972b), an individual discriminative stimulus (S[superscript D]) is composed of that S[superscript D]'s on-state plus the off-states of all other relevant S[superscript D]s. The present experiment investigated the reversibility of composite-stimulus control. Separate groups of rats…

We report a hitherto unknown form of side-specific learning in honeybees. We trained bees individually by coupling gustatory and mechanical stimulation of each antenna with either increasing or decreasing volumes of sucrose solution offered to the animal's proboscis along successive learning trials. Next, we examined their proboscis extension…

You may have observed that a small goldfish swimming in a spherical fishbowl can suddenly disappear. Why does this happen? The effect is due to total internal reflection. In this paper we find the locations of the fish and the observer's eye for which the fish cannot be seen.

After extinction of conditioned fear, memory for the conditioning and extinction experiences becomes context dependent. Fear is suppressed in the extinction context, but renews in other contexts. This study characterizes the neural circuitry underlying the context-dependent retrieval of extinguished fear memories using c-Fos immunohistochemistry.…

Rats were subjected to one or two cycles of context fear conditioning and extinction to study the roles of the prelimbic cortex (PL) and infralimbic cortex (IL) in learning and relearning to inhibit fear responses. Inactivation of the PL depressed fear responses across the first or second extinction but did not impair learning or relearning fear…

Albatrosses have evolved to soar and glide efficiently. By maximizing their lift-to-drag ratio "L/D", albatrosses can gain energy from the wind and can travel long distances with little effort. We simplify the difficult aerodynamic equations of motion by assuming that albatrosses maintain a constant "L/D". Analytic solutions to the simplified…