Forced-choice and free-choice trials in response priming with moving primes

Basically, we conducted a response priming experiment with moving row-of-dots-primes (motion direction: leftwards, rightwards, neutral [to the center or the boarders of the screen; inwards or outwards, respectively]; see Bermeitinger, 2013). In forced-choice trials, the target was a directional arrow (<< or >>) which has to be classified (leftwards or rightwards). In free-choice trials, the target was an ambigous arrow composition (<> or ><) and subjects should freely choose the left or right response.

Hypothesis: positive compatibility/congruency effects (PCE) with the shorter stimulus onset asynchrony (SOA) and reduced, perhaps even negative compatibility/congruency effects (NCE) with the longer SOA. (SOA was varied between subjects, short SOA = 147 ms, longer SOA = 360 ms.) In general, we expected the same pattern of results in forced-choice and free-choice trials.

Further, we set out to determine whether there are differences in the responses to trials with compatible neutral primes (i.e., inwards motions and >< targets; outwards motions and <> targets) and to trials with incompatible neutral primes (i.e., inwards motions and <> targets; outwards motions and >< targets).

Last but not least, we analyzed differences between >< and <> targets, focusing on leftwards and rightwards prime motions in free-choice trials. According to Cole and Kuhn (2010), responses should be faster or slower depending on the number of attentional turns needed between prime and response. For <> targets, we thus expected faster and more likely prime-congruent (than prime-incongruent) responses. In contrast, a >< target should result in faster and more probable prime-incongruent responses.

Results:
In forced-choice trials:
Compatible trials = primes and targets move/point in the same direction;
incompatible trials: primes and targets move/point in opposite directions;

In free-choice trials, congruency was determined by the responses given, i.e. congruent response = left/right button press after leftwards/rightwards motion; incongruent response = left/right button press after rightwards/leftwards motion.

Compatibility/congruency effect = response time in incompatible/incongruent trials - response time in compatible/congruent trials.

Stimulus Onset Asynchrony (SOA) = time from the beginning of the prime display to the beginning of the target display

We found (non-significant) PCEs in the short SOA (for forced-choice and free-choice trials) and (significant) NCEs in the longer SOA (for forced-choice and free-choice trials).
There were no congruency effects regarding neutral conditions (i.e. <> and outwards motion; >< and inwards motion).
For directional motions in free-choice trials, we found (non-significantly) faster prime-congruent than prime-incongruent responses after >< targets and the reverse (significant) result after <> targets (which is contrary to Cole & Kuhn, 2010).

本研究采用移动点阵启动刺激（运动方向分为向左、向右、中性三类：中性运动朝向屏幕中心或边缘，分别对应向内或向外运动，详见Bermeitinger, 2013）开展了反应启动实验。在迫选试次中，目标刺激为定向箭头（<<或>>），需被归类为向左或向右指向；在自由选择试次中，目标刺激为模糊箭头组合（<>或><），被试可自由选择左侧或右侧按键反应。

研究假设：短刺激呈现时间差（Stimulus Onset Asynchrony, SOA）条件下会出现积极相容性/一致性效应（Positive Compatibility/Congruency Effects, PCE）；长SOA条件下效应会减弱，甚至出现消极相容性/一致性效应（Negative Compatibility/Congruency Effects, NCE）。本研究在被试间操纵SOA时长，短SOA为147ms，长SOA为360ms。整体而言，我们预期迫选试次与自由选择试次会呈现一致的结果模式。

此外，本研究旨在探究相容中性启动试次（即向内运动与><目标、向外运动与<>目标的组合）与不相容中性启动试次（即向内运动与<>目标、向外运动与><目标的组合）的反应是否存在差异。

最后，本研究分析了><与<>两种目标刺激之间的差异，重点关注自由选择试次中启动刺激的向左、向右运动方向。根据Cole与Kuhn（2010）的研究，反应快慢取决于启动刺激与反应之间所需的注意转换次数。据此，我们预期<>目标会出现启动一致性反应更快、且更大概率出现启动一致性反应（相较于启动不一致性反应）；相反，><目标则会出现启动不一致性反应更快、且更大概率出现启动不一致性反应。

实验结果：
在迫选试次中：
相容试次：启动刺激与目标刺激运动/指向方向一致；
不相容试次：启动刺激与目标刺激运动/指向方向相反；

在自由选择试次中，一致性由被试给出的反应决定，即：一致性反应=向左/向右运动后按下左侧/右侧按键；不一致性反应=向左/向右运动后按下右侧/左侧按键。

相容性/一致性效应=不相容/不一致试次的反应时 - 相容/一致试次的反应时。

刺激呈现时间差（Stimulus Onset Asynchrony, SOA）= 启动刺激呈现起始时刻至目标刺激呈现起始时刻的时间间隔。

本研究发现：短SOA条件下（迫选与自由选择试次均如此）出现（未达显著水平的）PCE；长SOA条件下则出现（达显著水平的）NCE。中性条件下未观察到一致性效应（即<>目标与向外运动组合、><目标与向内运动组合）。在自由选择试次的定向运动条件中，我们发现：><目标试次中启动一致性反应快于启动不一致性反应，但该差异未达显著水平；而<>目标试次则出现相反结果（差异达显著水平），这与Cole & Kuhn（2010）的研究结论相悖。