The Neuron and Neural Firing

The key evidence is that the impulse occurs after threshold and is not larger when extra input is added.

all-or-none principle is the mechanism that makes "In a classroom demonstration, a neuron model fires only after enough small inputs are added..." coherent. The credited option, "Each impulse follows an all-or-none pattern once threshold is reached", is supported because The model shows threshold and a fixed-size impulse, which is the all-or-none principle. "Hormones travel only across synaptic gaps" is a real-looking alternative, but Hormones travel through the bloodstream, not only across synapses; "Myelin prevents communication between neighboring neurons" also fails because Myelin generally speeds neural transmission rather than preventing it. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.

The assigned condition is the independent variable; the measured task performance is the dependent variable.

The Neuron and Neural Firing reasoning here starts with "A researcher gives one group a drug that occupies dopamine receptors without activating them and gives..." and asks what mechanism fits. The credited option, "The independent variable, because it is the condition assigned by the researcher", is supported because The drug versus placebo condition is manipulated, so it is the independent variable. "The dependent variable, because it is the result recorded after the task" is a real-looking alternative, but The dependent variable is performance on the reward-learning task; "A confounding variable, because it is intentionally held constant across groups" also fails because The condition is intentionally varied, not held constant as a control. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.

The signal is not graded in partial sizes after the threshold is met.

The Neuron and Neural Firing reasoning here starts with "A cell stays quiet until stimulation crosses a minimum level; once crossed, the signal travels fully..." and asks what mechanism fits. The credited option, "All-or-none firing", is supported because A neural impulse either occurs fully or does not occur once threshold is reached. "Retinal disparity" is a real-looking alternative, but That is a binocular depth cue; "Self-efficacy" also fails because That is belief in one's capacity to carry out actions. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.