Final answer:
The Stroop effect is typically larger in individuals fluent in the language used for the test. An English-speaking participant with presumably high English proficiency (indicated by performing a 70) would demonstrate the largest Stroop effect due to the greater cognitive interference experienced in suppressing the automatic reading response.
Step-by-step explanation:
The question concerns the Stroop effect, which is a psychological phenomenon where the name of a color (e.g., "red", "blue", "green") is printed in a color not denoted by the name (e.g., the word "red" printed in blue ink) and individuals are asked to name the color of the ink. This task measures cognitive interference when the brain has to manage conflicting information.
The Stroop effect is generally more pronounced in individuals who are fluent in the language of the test, as their automaticity for reading words in their native language is higher, leading to greater difficulty in suppressing the automatic reading response to read the color of the ink instead. Given the choices presented, and assuming there are no other contributing factors, the English speaking participant performing a 70 would likely demonstrate the largest Stroop effect.
This assumption is made because the Stroop effect relies on familiarity with the language in question, and an individual speaking the language in which the test is administered would experience more interference compared to someone less familiar with the language. Participants are not described in detail nor are the numbers next to each participant explained, so we infer that '70' may refer to a group with the strongest proficiency in English compared to other groups denoted by '20', '30', and '80'.