Final answer:
A deer's inability to respond to car headlights is due to sensory overload, which occurs when too much sensory information overwhelms the sensory receptors.
Step-by-step explanation:
The deer's inability to respond to the headlights of an approaching car is due to a sensory phenomenon known as sensory overload. When a deer is caught in headlights, its eyes are suddenly flooded with bright light, causing the sensory receptors within the eyes to become overwhelmed. This overstimulation can lead to a temporary inability to react appropriately to the situation, as the deer's visual system is unable to process the sudden change in light quickly enough. This phenomenon is different from sensory adaptation, which occurs when sensitivity to a constant stimulus decreases over time, and selective attention, which involves focusing on a particular stimulus while ignoring others. In contrast to these, sensory overload occurs when an organism is bombarded with too much sensory information to process effectively.