The Interaction between Self-Bias and Reward: Evidence for Common and Distinct Processes

The perceptual matching of shapes and labels can be affected by both self- and reward-biases when shapes are linked either to labels referring to particular individuals (you, friend, stranger) or to different reward values (£8, £2, £0). We investigated the relations between these biases by varying the reward value associated with particular shape–label pairs (circle–you, square–friend, triangle–stranger). Self shape–label pairs (circle–you) always received no reward, while friend shape–label pairs (square–friend) received high reward and stranger shape–label pairs low reward (triangle–stranger), or the reverse (friend—low reward; stranger—high reward). Despite receiving no reward, responses to self-related pairs were advantaged relative to those to low-reward stimuli and did not differ from those to high-reward items. There was also an advantage for responses to high-reward friend pairs relative to low-reward stranger stimuli, and for high-reward stranger stimuli compared to low-reward friends. Correlations across individuals were found across trial blocks for both the self-advantage and the high-reward advantage, but the self- and reward-advantages were uncorrelated. This suggests that the self- and reward-advantage effects have different origins. In addition, the magnitude of the self-advantage varied according to the rated personal distance between a participant and a stranger. For individuals manifesting a close personal distance to strangers, the self-advantage was smaller, and sensitivity to reward influenced the difference between the self- and high-reward conditions. For individuals manifesting a large personal distance to strangers, sensitivity to reward did not affect self-matching. We suggest that self-advantages on perceptual matching arise independent of reward for individuals with a large personal distance to strangers. On the other hand, in individuals with a weak self-bias, high reward and the self modulate a common subjective value system.