The perception of accents and intelligence can be subjective and influenced by various factors such as cultural stereotypes, personal biases, and individual experiences. It is important to approach such perceptions with caution and avoid making generalizations about entire groups of people based on accent or dialect.
That being said, the perception you mentioned about Brummie accents (referring to the accent associated with Birmingham, England) may be a result of specific cultural or linguistic characteristics often associated with that accent. The unique features of the Brummie accent, such as vowel pronunciation and distinct intonation patterns, may contribute to the perception of sounding "thick" to some individuals.
However, it's important to note that the perception of wit or intelligence is not solely determined by accent or dialect. Intelligence is a complex and multifaceted trait that cannot be accurately judged based on linguistic variations alone. It is possible that the perception of Brummies having fast wit could stem from cultural associations, humor styles, or other factors unrelated to their accent.
It's crucial to remember that intelligence and wit are not inherent characteristics of any specific accent or dialect. They vary among individuals regardless of their regional or linguistic background. It is always important to approach such perceptions with an open mind and treat each person as an individual rather than making generalizations based on their accent.