Sunday, June 24, 2007

Arousal Takes Time: Insight from Latencies

Instead of doing the work I had to do Saturday, I spent some of the day working on old data. I love to work on data, so this was a much better way to spend the late afternoon.

These data kept bringing me back to time. Time matters a lot.

In a recently published article, Dynamic, embodied limited-capacity attention and memory: Modeling cognitive processing of mediated stimuli (read PDF here), I make an argument that time matters.

But I do not really do time justice in the model. Time matters a lot more than even I have acknowledged.

Consider the current data. We showed participants 30-second television clips varying in valence and arousal. Thus, positive and negative clips were shown that varied in arousal. In total, there were 5 levels of arousal.

After each clip, we asked participants how arousing the clip was, how negative the clip was, and how positive the clips was. These were 7-point scales ranging from "very" to "not at all."

The question is, how do you make that decision? How do you decide how arousing/exciting a clip was? Do you search your memory? And, of course, the most interesting question to me is: how do you search your memory?

If something was really arousing, then judging its arousal value should be easy, right?

Wrong, it turns out.

You see, arousal is not just another variable. It is exactly what I argue it is in the Media Psychology article cited above: a dynamic, embodied variable.

Imagine if I ask you how often you see a co-worker. Presumably, you see her five days a week. So as soon as you attempt to search your memory, you are going to immediately retrieve many exemplars of that co-worker.

So it's an easy question. It's also an easy question if I ask you how often you see someone that you rarely see.

But what about someone you see somewhat regularly?

In several data sets that we have (and the data of others, such as Ohio State's Russ Fazio), those moderate decisions take more time to make.

But arousal, as I stated above, is not just another variable. Instead, physiological arousal gets you going. It helps you move. It pumps the heart to get oxygen to muscles all over the body. Fight-or-flight is driven by arousal. When you watch something arousing on television, it reaches in and grabs a hold of your sympathetic nervous system and shouts: do something!

So when I ask you how arousing something was, you should begin to think about that thing. And if the stimulus was really arousing and you try to access that memory -- especially the memory of how arousing it was -- the memory should trigger the earlier arousal.

And that triggered arousal should invoke automatic cognitive processes that attempt to divert limited capacity attentional resources away from the arousal-judging task and to the stimulus itself.

If this is the case, then arousal judgments should get slower as the original stimulus became more arousing. If the subsequent judgments are only a matter of "counting" how many arousal-related features were in the original message, then those judgments should speed up as a function of arousal.

Our data support the first interpretation. See the figure above. As the content became more arousing (i.e., as the label on the X-axis increases from 1 to 5), the latency of the response increases from 2,300 ms to 2,700 ms. Thus, it took these participants almost a half second longer to make arousal judgments about arousing stimuli. And those seem like the easier decisions.

Although the figure is far from perfectly linear, the linear trend is strongest, F(1,53) = 10.82, p = .002, eta-squared = .17 (sorry non-stats readers). And this is for raw response latencies. That is, these data include trials where participants started daydreaming and took 30 seconds to answer the question.

Time matters. Sure, if you look at the self-report data, the arousing content was rated as more arousing (also a linear trend). But the answers to the questions do not tell the entire story. I need to know what you responded, and how look it took you to do it. The response latency data help tell the story.

Emotion is not just something we manipulate in the lab, as Peter J. Lang once argued during an address to the Society for Psychophysiological Research. Instead, emotion is a property of the individual. Emotion is a survival-oriented trait that helps keep our eyes focused when attention is crucial and allows them to wander when surveying the landscape is more adaptive.

I've tried to keep a focus on time, but I am realizing now that I have not done enough. Time is on my mind. I hope it's on your mind, too.

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