Attention biases decisions but does not alter appearance

Abstract

Recently, M. Carrasco, S. Ling, and S. Read (2004) reported that transient visual attentional cues could increase the perceived contrast of Gabor grating targets. We replicated their study using their exact stimuli and procedures. While we were able to reproduce their results, we discovered that the reported attentional effects vanished when we changed the type of decision that subjects performed from a comparative judgment ("which target has higher contrast?") to an equality judgment ("are the two targets equal in contrast?") that is resistant to bias. To ensure that the difference between the judgments was not due to a difference in attentional strategies, we also performed a control experiment in which subjects were instructed on a trial-by-trial basis which judgment to perform only after the stimuli had disappeared. In this experiment, the magnitude of attentional effect for the comparative judgment was diminished but still significant and the equality judgment still measured no effect. We conclude that the reported effects of attention upon appearance can be entirely explained by decision bias, and that attention does not alter appearance.

Exogenous visual attention prolongs perceived duration

“…With a spatially overlapping cue and target, we could not detect an attention effect on perceived duration, but we also could not observe a reversed attention effect. Hence, even though we cannot provide a conclusive explanation for why Chen and 5 In Schneider and Komlos (2008), the PSE was determined from fitting the individual data to a difference of cumulative normal distribution functions. Since the individual functions in Experiment 6 tended to be asymmetrical (such asymmetrical functions are not uncommon in the literature on perceived duration; see, e.g., Wearden, 2004), such a parametric approach was not feasible.…”

“…Specifically, Schneider and Komlos (2008) had suggested that cued-that is, attendedstimuli might be assigned a higher priority, giving participants a preference for "longer" responses. With a comparison judgment task, a true prolonging effect of attention on perceived duration and such a response bias cannot be distinguished.…”

“…In this task, they presented the participants only one temporal interval per trial and asked them to classify this interval as "short", "medium", or "long". In Experiment 4, we assessed whether the reversed attention effects could be attributed to this difference in methodology, because several psychophysical studies have suggested that the results of such studies may depend on the exact judgment task (e.g., Allan, 1979;Schneider & Komlos, 2008;Zakay, 1993).…”

“…Nevertheless, it is possible to attribute this effect to a decision bias, rather than to a genuine attention effect on perceived duration. Specifically, Schneider and Komlos (2008) argued that cuing paradigms in combination with comparative judgments, as used in the previous experiments, can be prone to criterion effects. Schneider and Komlos argued that attention, as directed by a cue, might not necessarily influence perceived duration but could also change the response pattern by influencing decision mechanisms.…”

“…In short, attention might prioritize the corresponding target and increase participants' preference for a "longer" response. Schneider and Komlos (2008) demonstrated, within the framework of a plausible mathematical model, that an equality judgment, rather than a comparison judgment, can deconfound such a criterion and genuine attention effects. Therefore, in Experiment 6, we employed an equality 4 Experiment 5 suggested that the effect of exogenous cuing on perceived duration varies between participants.…”