Tuesday, November 13, 2012

Evidence for Unconscious Math, Language Processing Abilities

Summary from Slashdot

"It's hard to determine what the unconscious brain is doing since, after all, we're not aware of it. But in a neat set of experiments, researchers from the Hebrew University of Jerusalem's consciousness lab found evidence that the unconscious brain can parse language and perform simple arithmetic. The researchers flashed colorful patterns at test subjects that took up all their attention and allowed for the subliminal presentation of sentences or equations. In the language processing experiment, researchers found that subjects became consciously aware of a sentence sooner if it was jarring and nonsensical (like, for example, the sentence 'I ironed coffee')."

Research by Hebrew University Consciousness Lab




Your Unconscious Brain Can Do Math, Process Language

POSTED BY: Eliza Strickland
 The unconscious brain may not be able to ace an SAT test, but new research suggests that it can handle more complex language processing and arithmetic tasks than anyone has previously believed. According to these findings, just published in the Proceedings of the National Academy of Sciences, we may be blithely unaware of all the hard work the unconscious brain is doing.

In their experiments, researchers from Hebrew University in Israel used a cutting-edge "masking" technique to keep their test subjects from consciously perceiving certain stimuli. With this technique, known as continuous flash suppression, the researchers show a rapidly changing series of colorful patterns to just one of the subject's eyes. The bright patterns dominate the subject's awareness to such an extent that when researchers show less flashy material to the other eye (like words or equations), it takes several seconds before the brain consciously registers it.

This masking technique is "a game changer in the study of the unconscious," the scientists write, "because unlike all previous methods, it gives unconscious processes ample time to engage with and operate on subliminal stimuli."

To study the unconscious brain's ability to process language, the researchers subliminally showed the subject short phrases that made variable amounts of sense: For example, subjects might see the phrase "I ironed coffee" or "I ironed clothes." The researchers gradually turned up the contrast between the phrase and its background, and measured how long it took for the phrase to "pop" into the subject's conscious awareness. As the nonsensical phrases popped sooner, the researchers hypothesize that the unconscious brain processed the sentence, found it surprising and odd, and quickly passed it along to the conscious brain for further examination.

To determine the unconscious brain's mathematical abilities, the researchers presented a simple subtraction or addition equation (for example, "9 3 4 = ") to a subject, but took it away before it could pop into consciousness. Then they stopped the masking pattern and displayed a single number, asking the viewer to pronounce the number as soon as it registered. When the number was the answer to the subtraction equation (for example, "2"), the subject was quicker to pronounce it. The researchers argue that the viewer was "primed" to respond to that number because the unconscious brain had solved the equation. Oddly, they didn't find the same clear effect with easier addition equations. 

Why is IEEE Spectrum covering this? We could argue that until we understand the workings of consciousness in the human brain, we'll never be able to build an artificial intelligence that can be described as conscious and aware. Or we could admit that we just thought the study was nifty.


 Reading and doing arithmetic nonconsciously

  1. Ran R. Hassina,c,2
+ Author Affiliations
  1. aPsychology Department,
  2. bCognitive Science Department, and
  3. cCenter for the Study of Rationality, Hebrew University, Jerusalem 91905, Israel
  1. Edited* by Michael I. Posner, University of Oregon, Eugene, OR, and approved October 5, 2012 (received for review July 12, 2012)


The modal view in the cognitive and neural sciences holds that consciousness is necessary for abstract, symbolic, and rule-following computations. Hence, semantic processing of multiple-word expressions, and performing of abstract mathematical computations, are widely believed to require consciousness. We report a series of experiments in which we show that multiple-word verbal expressions can be processed outside conscious awareness and that multistep, effortful arithmetic equations can be solved unconsciously. All experiments used Continuous Flash Suppression to render stimuli invisible for relatively long durations (up to 2,000 ms). Where appropriate, unawareness was verified using both objective and subjective measures. The results show that novel word combinations, in the form of expressions that contain semantic violations, become conscious before expressions that do not contain semantic violations, that the more negative a verbal expression is, the more quickly it becomes conscious, and that subliminal arithmetic equations prime their results. These findings call for a significant update of our view of conscious and unconscious processes.


  • Author contributions: A.Y.S., N.L., A.G., R.M., A.M., and R.R.H. designed research; A.Y.S., N.L., A.G., R.M., and A.M. performed research; A.Y.S., N.L., A.G., and R.M. analyzed data; and A.Y.S. and R.R.H. wrote the paper.
  • The authors declare no conflict of interest.
  • *This Direct Submission article had a prearranged editor.
  • To control for the effects of the single words on popping times, we conducted a regression with expressions' affective value, the mean affective value of the individual words, and the length (number of letters) of the expression. The model was marginally significant [F(3,42) = 2.804, P = 0.051]. Word affectivity and length did not predict popping times (P > 0.3). The expression's affective value, however, remained a significant predictor [β = 0.377, t(42) = 2.627, P = 0.012]. The same analysis for Experiment 4b yielded similar results: a significant model [F(3,42) = 8.666, P < 0.001] and a significant effect of the expressions' affective value [β = 0.353, t(42) = 2.856, P = 0.007]. The valence of the single words and their length also predicted popping times [β = −0.294, t(42) = −2.380, P = 0.022 and β = −0.441, t(42) = −3.634, P = 0.001]. Importantly, these analyses show that the affective value of multiple-word expressions predicts popping time, even when the effects of the single words are statistically controlled.
  • To further examine awareness, we regressed subtraction facilitation scores (RTs for incongruent minus congruent trials) on objective block scores (centered so that a score of zero indicated chance level) (39). The results showed significant facilitation when accuracy in the objective block is at chance [βintercept = 14.78, t(15) = 3.91, P = 0.001] and insignificant slope [β = 86.85, t(15) = 1.47, P = 0.161].
  • §This explanation was verified in the pilot described. The results showed that addition equations were, indeed, solved faster than subtraction equations [mean = 1,795.01 ms, SD = 274.36 and mean = 2,167.78 ms, SD = 494.33, respectively; t(20) = 3.69, P = 0.001].
  • As a group, participants fared better than chance on the objective block (P < 0.01). However, there was a significant negative correlation between facilitation scores and objective block scores (r = −0.39, P = 0.032). Awareness of the equations, then, reduced facilitation, thereby working against the hypothesized effect. Another way of verifying that subtle awareness is not producing the effects is to use the regression method described above. This analysis showed significant facilitation, even when accuracy in the objective block was at chance [βintercept = 20.32, t(29) = 3.33, P = 0.002].
  • One other possible difference between addition and subtraction is that magnitude matters. The solutions to addition equations were larger than the solutions for subtraction equations and hence, more difficult to compute. The data, however, show no differences between addition equations that yielded high vs. low solutions (all P values > 0.17). These results suggest that magnitude does not play a crucial role here.
  • **There was a marginal effect on RTs (P = 0.08), raising the possibility that participants were also slower on incompatible trials. This result may suggest that the presentation of nonconscious equations results in strategic changes in processing. Because this effect was not hypothesized, we do not wish to make much of it.
  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1211645109/-/DCSupplemental.