Final answer:
The person likely forgot Jean's husband's name due to retroactive interference from engaging in a conversation with an old friend, which represents a memory error where new information hinders the recall of older information.
Step-by-step explanation:
The person forgot Jean's husband's name at the party most likely due to interference from talking to an old friend. Interference is a common reason for forgetting and occurs when one memory competes with another, causing one of the memories to be more difficult to recall.
This concept is supported by the fact that our memory system is flexible and prone to errors, as explained in various studies of memory.
There are two types of interference: proactive interference and retroactive interference. In the given scenario, likely, the conversation with the old friend (a newer piece of information) interfered with recalling the husband's name (an older piece of information), demonstrating retroactive interference. Interference can easily disrupt our ability to recall even well-known details such as names, leading to such memory errors in social situations.