Evidence of SQUARC and distance effects in a weight comparison task

Abstract

Stimuli associated with large quantities are typically responded to faster with a right- than a left-side key, whereas stimuli associated with small quantities are typically responded to faster with a left- than a right-side key. This phenomenon is known as the spatial-quantity association of response codes (SQUARC) effect. Here, in two experiments, we explored whether a SQUARC effect can emerge for light versus heavy items. Participants judged whether the weight associated with a central target word, describing an animal (e.g. ‘cow’; Experiment 1) or a material (e.g. ‘iron’; Experiment 2), was lighter or heavier than the weight associated with a reference word. Responses were provided with a left- and a right-side button. Then, participants estimated the weight associated with target and reference words. In both experiments, evidence for a SQUARC effect emerged. Moreover, response times for each target word decreased with absolute difference between its rated weight and the rated weight of the reference word, in line with a distance effect. Overall, these results provide evidence of a possible spatial representation of weight.

Appendix

The strength of the SQUARC effect was computed through the following equation:

$${\text{SQE}}_{i} =\left[ {{\text{RT}}_{i} \left( {{\text{heavy}},{\text{left}}} \right) - {\text{RT}}_{i} \left( {{\text{heavy}},{\text{right}}} \right)} \right]{\text{ }} +\left[ {{\text{RT}}_{i} \left( {{\text{light}},{\text{right}}} \right) - {\text{RT}}_{i} \left( {{\text{light}},{\text{left}}} \right)} \right]$$

where SQE_i stands for the strength of the SQUARC effect for the ith participant. RT_i(heavy, left) and RT_i(heavy, right) stand for the average RTs for the ith participant when she/he responded to ‘heavier’ target words with the left-side key and the right-side key, respectively. RT_i(light, right) and RT_i(light, left) stand for the average RTs for the ith participant when she/he responded to ‘lighter’ target words with the right-side key and the left-side key, respectively. The SQE_i increases with the strength of the association between ‘heavier’ (‘lighter’) words and the right-side (left-side) response. A negative SQE_i would indicate the presence of an inverted SQUARC effect.