Two primes priming: Does feature integration occur before response activation?

Abstract

Responses to a target can be sped up or slowed down by a congruent or incongruent prime, respectively. Even though presentations are rapid, the prime and the target are thought to activate motor responses in strict sequence, with prime activation preceding target activation. In feature fusion, the opposite seems to be the case. For example, a vernier offset to the left is immediately followed by a vernier offset to the right at the same location. The two verniers are not perceived as two elements in sequence but as a single, aligned vernier. Here, we ask the question as to how features are integrated: before or after motor activation? We presented two vernier primes with opposite offset directions preceding a single vernier target. No priming effect occurred when the vernier primes were presented at the same location, indicating that verniers integrate before motor activation. There was also no priming effect when the primes were presented simultaneously at different locations, indicating that there is an integration stage different from the perceptual fusion stage. When the second prime is delayed, it determines priming, even for very long delays. To explain these long integration times, we argue that there is a buffer preceding motor activation.

Temporal dynamics of sequential motor activation in a dual-prime paradigm: Insights from conditional accuracy and hazard functions

“…It is important to point to the different insights that can be gained from an ANOVA on mean correct RT, versus an event history analysis. First, in accordance with the conclusions from previous findings (Breitmeyer & Hanif, 2008;Grainger et al, 2013), a second prime dominates the priming effect in mean correct RTs and ER, at least for short interprime intervals. However, the event history analysis showed that the first prime dominated the motor response in the earliest bins (Experiment 1).…”

“…Intermediate responses should be influenced by the second prime. From previous data, we expected that the second prime would dominate the response at the shortest P1-P2 SOA (i.e., the longest P2-T SOA), and this dominance of the second prime should decrease with increasing P1-P2 SOA because the first prime has progressively more time to activate a response before the second prime occurs, while the second prime has progressively less time before the target occurs (Grainger et al, 2013).…”

“…Grainger, Scharnowski, Schmidt, and Herzog ( 2013 ) employed two 20-ms Vernier stimuli as primes. In a series of experiments, they found that (1) two primes presented in immediate succession at the same location integrate before activating a motor response, and do not cause sequential activation; (2) two identical primes yield larger priming effects than single primes; (3) one consistent and one inconsistent prime presented simultaneously at different locations cancel each other’s effects.…”

“…Such a simple feedforward-sweep model seems to account very well for response priming effects at short SOAs (up to 100 ms), but would predict unrealistically high error rates for longer SOAs (because in inconsistent trials, the prime would always have enough time to drive the wrong response to completion). Therefore, priming effects at longer SOAs are more plausibly carried by the content of a response buffer that carries information from both primes, but is dominated by the second one (Grainger et al, 2013 ). This buffer would allow participants to delay their responses, waiting out the target.…”

Invisibility and interpretation

“…The invisible vernier target offset is even integrated with offsets of flanking elements, which can be presented more than 400 ms after target onset, which is much longer than the reaction times in mask priming experiments. We have recently shown that feature fusion even precedes motor-priming (Grainger et al, 2013). As in the TMS experiment above, the sequential metacontrast paradigm shows that features of invisible elements can persist in the human brain for substantially long times.…”