Invisible Nudes Redux

No, the invisible nudes are not taking Redux [although visible nudes might be], rather the PNAS paper on sex, sexual orientation, and implicit attentional priming by naked pix has finally been posted online:

Yi Jiang, Patricia Costello, Fang Fang, Miner Huang, and Sheng He. A gender- and sexual orientation-dependent spatial attentional effect of invisible images. Proc. Natl. Acad. Sci. Published online before print October 30, 2006.

Human observers are constantly bombarded with a vast amount of information. Selective attention helps us to quickly process what is important while ignoring the irrelevant. In this study, we demonstrate that information that has not entered observers' consciousness, such as interocularly suppressed (invisible) erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation. While unaware of the suppressed pictures, heterosexual males' attention was attracted to invisible female nudes, heterosexual females' attention was attracted to invisible male nudes, gay males behaved similarly to heterosexual females, and gay/bisexual females performed in-between heterosexual males and females.

As mentioned previously, the experiment took advantage of binocular rivalry. Here, the presentation of "noisy" visual stimuli to both visual fields in one eye (and to half the visual field in the other eye) suppresses the naked body, making its perception unconscious (see figure above for an example). Or as the authors explain it:

In the interocular suppression paradigm, a pair of high-contrast dynamic noise patches are presented to both sides of a fixation point in one eye, and a test picture and its scrambled control are presented to the fellow eye in spatial locations corresponding to the noise patches. Because of strong interocular suppression, the intact meaningful image and its scrambled control remain invisible for the period they are presented. If the suppressed images exert a location-specific effect on the attentional system, these images could potentially act as attentional cues that would influence the distribution of spatial attention and thus performance on a subsequent detection task.

As illustrated in the complete figure below, the task is to determine the line orientation of lateralized target stimuli presented after the cue. The idea is that if spatial attention was unconciously drawn to the preferred nude [either male or female... or maybe both], subsequent performance for targets presented to the same visual field would improve.

Now let's discuss the study's participants, since the major selection criterion influenced the results. Forty people participated: 10 straight men, 10 straight women, 10 gay men, 10 gay/bisexual women. So already, your conclusions about gay females are limited, because this group included both lesbians and bisexuals. Authors' description:

Ten heterosexual men and 10 heterosexual women participated in experiment 1. Ten gay men (an average score of 5.6 on the Kinsey scale; 0 is exclusively heterosexual, 3 is equally heterosexual and homosexual, and 6 is exclusively homosexual) and 10 gay-bisexual women (with an average Kinsey score of 4.5) participated in experiment 2.

This is crap!

(1) A minor qibble: fortunately the straight and gay individuals performed the same task, but it's false to say they participated in two separate experiments.
(2) What is the Kinsey rating for the heterosexuals? [that's not apparent until Fig. 4, when one can see it's zero]
(3) Why didn't they match gay men and women on the Kinsey scale?? [You can read more about the Kinsey scale in a previous post on the Ponsetti porn study.]

All right, let's look at the results. The figure below shows the correlations between attentional bias (female greater than male = positive number, and vice versa) and Kinsey score for men (top) and women (bottom). Yes, they're both significant, but some things to note: the graphs are on different scales, the bi women show a bias towards males, and the bias for the Kinsey 5-6 lesbians is zero. Hmm. For heterosexuals,
Specifically, male observers were more accurate at the orientation discrimination task when the Gabor targets followed the site of the invisible nude female pictures (attentional benefit) and were less accurate when the Gabor patches were at the site of invisible nude male pictures (attentional cost). In other words, heterosexual male observers’ attention was attracted to nude female images (positive attentional effect) and was repelled from nude male images (negative attentional effect), even though the images were not consciously perceived by the observers. Similarly, female participants showed an attentional benefit (attraction) to invisible nude male pictures (positive attentional effect), although they did not show a significant attentional effect to invisible nude female pictures.

OK. But then the authors don't bother to analyze the data from gay participants in the same way. They show a scatterplot with all four groups (good), then launch into a bootstrapping analysis (to compensate for the low n's in each cell, perhaps... comments from statistics gurus are welcome here).
One conclusion:

These results clearly show that spatial distribution of observers’ attention can be modulated by the presence of certain types of visual images even when the images are interocularly suppressed and invisible. Furthermore, such attentional effect is not a general rise in alertness but is very specific both spatially and in terms of the gender and sexual orientation of the observer. Observers’ attention could either be attracted to or repelled from an invisible erotic image depending on their gender and sexual orientation.

Um, no.

According to the evolutionary perspective, unpredictable distributed resources and dangers enjoy privileged processing, and significant emotional stimuli such as food, mating partners, or signals of threat should be particularly effective cues for capturing attention. Results from the current study suggest that even in the absence of awareness, the emotional system processes information in a very specific fashion, both in terms of representing the spatial location and in terms of coding the gender information of the image content. A salient image does not uniformly affect attention; rather, it either attracts or repels attention. This finding contrasts with the general effect of orienting attention toward salient stimuli.

No, no, make it stop! The authors should be forced to watch Let's Go to Prison on a continuous loop until they recant their evolutionary speculations.

Then they go on to muse about the neural correlates of these effects (i.e., amygdala), even though neuroimaging was not conducted.

SUMMARY from The Neurocritic: Ugh.