With only two goods, if the income effect is in the same direction as the substitution effect then the good is

Normal good

Explanation:

Income effect Is change in quantity demanded when the consumers purchasing power change as a result of a change in real income.

Substitution effect is when quantity demanded falls as a result of rise in price of a good which leads consumers to purchase cheaper alternatives.

A normal good is a good whose demand increases as income increases.

If the price of a normal good falls, the real purchasing power of the consumer increases and the consumer buys more of the good. Also, the consumer substituites from more expensive alternative goods to the more cheap normal good. The income and substitution effect both move in the same direction.

in terms of experimental research, mcdonald’s charging different prices in the two cities relates to