Three experiments were conducted to test an interpretation of the response-rate-reducing effects of unsignaled nonresetting delays to reinforcement in pigeons. According to this interpretation, rates of key pecking decrease under these conditions because key pecks alternate with hopper-observing behavior. In Experiment 1, 4 pigeons pecked a food key that raised the hopper provided that pecks on...

This study experimentally examines the flow of glass spheres in a wedgeshaped hopper that is vibrated horizontally. When the hopper is discharged without vibration, discharge occurs as a hnnel flow, with the material exiting the central region of the hopper and stagnant material along the sides. With vibration, the discharge of the material occurs in reverse, with the material along the sides e...

Pigeons rapidly acquire a key-pecking response when 8-sec illuminations of a response key precede each presentation of grain (Brown and Jenkins, 1968). Bilbrey and Winokur (1973) and Winokur and Boe (1975) have reported that such autoshaped responding does not occur when grain presentation is preceded by a tone, either presented from a speaker separate from the response key or from a speaker be...

Idioscopus clypealis (Lethierry) is commonly known as mango leaf hopper. The hopper reduces mongo production by causing non setting of flower and dropping of immature fruits. The first appearance of hoppers (0.12 and 0.16) on the branches of mango trees was recorded in February which is correlated with increase in maximum (23.89 degrees C and 24.29 degrees C) and minimum temperature (11.46 degr...

Recent experiments by Baxter et al. showed the existence of density waves in granular material flowing out of a hopper. We show, using Molecular Dynamics Simulations, that this effect is a consequence of static friction and find that these density fluctuations follow a 1/f spectrum. The effect is enhanced when the opening angle of the hopper decreases.

The struggle for gender equality ranks as one of our century's defining movements. This struggle has won women in Canada and around the developed world the right to vote, to own property, to earn an education, and to work outside the home for wages. It has also won them the right to physical safety within their own homes. Where men once had the legal right to beat their wives with a stick no th...