Abstract

Past research has reliably established that rewards exert an influence on overt/observable behaviours (e.g., explicit choices, limb/body movements, eye- movements). Oftentimes, a reward may be acquired by performing a specific behaviour in response to a visual target. Under such circumstances, research has demonstrated that the reward covertly influences the late neural stages of information processing along the “visual perception-overt behaviour” continuum (e.g., the motor processing immediately preceding the performance of the overt behaviour needed to acquire the reward associated with the perceived visual target).
Only recently has research also begun to investigate whether reward covertly influences the earlier neural stages of information processing along the “visual perception-overt behaviour” continuum (i.e., the visual perception of the target stimulus). Such research has suggested that reward does indeed influence even the earliest form of visual perception (i.e., feature perception). This conclusion has been drawn form the handful of documented effects of reward on certain behavioural measures of performance during feature singleton visual search (e.g. the observation of slower key-press responses for targets associated with low than with high monetary reward). However, since the key- press response is a motor response, such results may entirely or partially reflect reward influences on the motor (i.e, late) as opposed to the perceptual (i.e, early) information processing stage. Other evidence, suggestive of the effects of reward on feature visual perception, stems from the documented effect of reward on attention (i.e., the N2pc, a reliable marker of attentional selection of visual targets, appears later and is weaker for low than for high reward targets), given attention’s independently documented effects on feature visual perception.
The aim of the current study was to provide a more thorough behavioural assessment of reward influences on visual perception in feature singleton visual search (within the magnitude and probability dimensions). A measure of sensitivity (d’), reflective of perceptual rather than motor processing, was added to the behavioural measures used in past studies and was shown to be poorer for low than high reward targets. This finding suggested that low reward targets are visually perceived later than high reward targets are. Sensitivity was correlated with accuracy and inverse efficiency, suggesting that the observed variations in those measures as a function of target reward value reflected the same or similar underlying process as sensitivity did. Furthermore, shortening display duration across visual search trials was more detrimental to such behavioural performance for low than high reward targets, further suggesting that low reward targets are visually perceived later than high reward targets are (either via direct channels, via attention or both). In summary, this more thorough behavioural assessment of reward influences on visual feature perception corroborated the conclusions drawn in the existing literature.