Monday, May 25, 2009

Massage stimulates brain development

I've always been a massage nut. Many years ago I had some formal training, and I always feel totally rejuvenated by the too-infrequent massages I occasionally get. This item in the Journal of Neuroscience from Guzzetta et al. makes perfect sense to me. I'll bet that a shadow of these early effects of massage seen in infants still occur in adults. The brain growth factor (IGF-1) enhanced by massage in infants is also associated with brain plasticity in adult humans:
Environmental enrichment (EE) was shown recently to accelerate brain development in rodents. Increased levels of maternal care, and particularly tactile stimulation through licking and grooming, may represent a key component in the early phases of EE. We hypothesized that enriching the environment in terms of body massage may thus accelerate brain development in infants. We explored the effects of body massage in preterm infants and found that massage accelerates the maturation of electroencephalographic activity and of visual function, in particular visual acuity. In massaged infants, we found higher levels of blood IGF-1. Massage accelerated the maturation of visual function also in rat pups and increased the level of IGF-1 in the cortex. Antagonizing IGF-1 action by means of systemic injections of the IGF-1 antagonist JB1 blocked the effects of massage in rat pups. These results demonstrate that massage has an influence on brain development and in particular on visual development and suggest that its effects are mediated by specific endogenous factors such as IGF-1.

SenseCam - a device for restoring and protecting memories

While scanning my lost list of articles that might become the topic of MindBlog posts, I re-encountered this description from Science Magazine of research on autobiographical memory which has subjects wear a small camera mounted on their chests. The work has expanded to involve patients with memory problems due to Alzheimer's or brain injuries. On viewing the camera's data six months later:
...many SenseCam users...report a sudden flood of memories of thoughts and sensations, ... "Proustian moments," when they review images taken by the device. SenseCam's images correspond to the nature of human memory--they're fragmentary, they're formed outside conscious control, they're visual in nature, they're from the subject's perspective. All these features are very like what we call episodic memory.

SenseCam records images passively, permitting a person to go about their day without interruption. The latest version is about the size and weight of a clunky mobile phone and appears to observe the world through two unmatched eyeballs. One is a passive infrared sensor, tuned to trigger the camera whenever another person passes by. The other is a wide-angle camera lens, set to capture most of the user's field of view. The device is also equipped with an ambient light sensor that triggers the camera when its user moves from one room to another, or goes in or out of doors. The camera can also be set to snap an image if the sensors haven't triggered a photo after an arbitrary number of seconds. A typical wearer might come home with 2000 to 3000 fragmentary, artless images at the end of a day.
A research team:
...under the direction of neuropsychologist Georgina Brown, has followed five additional people with memory problems over a nearly 3-year period, exploring the difference between the memory boost provided by visual and written diary-keeping. Establishing a baseline of how fast these people lose their memories, the team asked each about an event every other day for 2 weeks after the event, and then again after 1 month and after 3 months. Then they asked the patients to keep a diary of a separate event and review it every other day during an initial 2-week assessment, but not during subsequent months. Finally, patients reviewed their SenseCam's images for 2 weeks following a third event.

The preliminary results suggest that SenseCam use strengthened these patients' memories more than diary-keeping did. A full analysis of the data is in preparation, says Brown, whose team plans to submit it to the journal Memory for a special issue devoted to SenseCam research.

Friday, May 22, 2009

What we will never be able to talk about - Ineffability

At numerous points during my reading of Thomas Metzinger's new book "The Ego Tunnel" I have come across writing that seems such a crisp description of core ideas (as well as being directly relevant to my own experience) that I want to try to condense and pass the material on to you. I found the following mix of summary, paraphrase, and quotes from chapter 2 to be a calming antidote to my implicit and constant "I can understand this" temperament. (By the way, I first bought this book for my Kindle but then found that the kind of jumping back and around, checking references, that I want to do in reading such a book was impossible, so I purchased the hard copy.) Here's a chunk on the ineffability problem:
In between 430 and 650 nanometers, we can discriminate (make same/different judgements about) more than 150 different wavelengths, or different subjective shades of color. But, if asked to reidentify single colors with a high degree of accuracy, we can do so for fewer than 15. The same is true for other sensory experiences. We can discriminate about 1,400 steps of pitch difference across the audible frequency range, but we can recognize these steps as examples of only about 80 different pitches... Thus we are much better at discriminating perceptual values than we are at identifying or recognizing them.

Metzinger uses a simplest example of two similar shades of green to spell through the consequences of this situation (he calls them Green No. 24 and Green No. 25, nearest possible neighbors on the color chart, such that there's no shade of green between them that you could discriminate). We can experience their difference, but are unable consciously to represent the sameness of Green No. 25 over time. We do not possess introspective identity criteria for this simplest state of consciousness, and we can not pinpoint a minimally sufficient neural correlate of Green No. 25 in the brain if we can not correctly identify the phenomenal aspect of Green No. 25 over time, in repeated trials in a controlled experimental setting. This is why it may be impossible to do what most hard scientists in consciousness research would like to do: show that Green No. 25 is identical with a state in your head.

These simple findings show that there is a depth in pure perception that cannot be grasped or invaded by thought or language. This ineffability problem arises for the simplest forms of sensory awareness, for the finest nuances of sight and touch, of smell and taste, and for those aspect of conscious hearing that underlie the magic and beauty of a musical experience. It almost certainly appears also for empathy, for emotional and intrinsically embodied forms of communication.

Money doesn't make us happy, certainty does.

A nice Op-Ed piece from Daniel Gilbert in the N.Y. Times. It is found on the New York Time's blog "Happy Days" - a discussion about the search for contentment in its many forms — economic, emotional, physical, spiritual. This blog was running postings through 2006, and then curiously lapsed until this Gilbert article. Gilbert's conclusions:
Our national gloom is real enough, but it isn’t a matter of insufficient funds. It’s a matter of insufficient certainty. Americans have been perfectly happy with far less wealth than most of us have now, and we could quickly become those Americans again — if only we knew we had to.

Why would we prefer to know the worst than to suspect it? Because when we get bad news we weep for a while, and then get busy making the best of it. We change our behavior, we change our attitudes. We raise our consciousness and lower our standards. We find our bootstraps and tug. But we can’t come to terms with circumstances whose terms we don’t yet know. An uncertain future leaves us stranded in an unhappy present with nothing to do but wait.

Thursday, May 21, 2009

Status is everything?

Tierney describes how Geoffrey Miller continues the arguments he started in "The Mating Mind" which seek to reduce much of our behavior to a quest for sex and status. His new book is “Spent: Sex, Evolution and Consumer Behavior.” This is a complementary approach to the sort of material mentioned in Monday's post on Gopnik's article.
If marketers (or their customers) understood biologists’ new calculations about animals’ “costly signaling,” ... they’d see that Harvard diplomas and iPhones send the same kind of signal as the ornate tail of a peacock....Sometimes the message is as simple as “I’ve got resources to burn,” the classic conspicuous waste demonstrated by the energy expended to lift a peacock’s tail or the fuel guzzled by a Hummer. But brand-name products aren’t just about flaunting transient wealth. The audience for our signals — prospective mates, friends, rivals — care more about the permanent traits measured in tests of intelligence and personality.

In a series of experiments, Dr. Miller and other researchers found that people were more likely to expend money and effort on products and activities if they were first primed with photographs of the opposite sex or stories about dating...After this priming, men were more willing to splurge on designer sunglasses, expensive watches and European vacations. Women became more willing to do volunteer work and perform other acts of conspicuous charity — a signal of high conscientiousness and agreeableness, like demonstrating your concern for third world farmers by spending extra for Starbucks’s “fair trade” coffee.

To get over your consuming obsessions, Dr. Miller suggests exercises like comparing the relative costs and pleasures of the stuff you’ve bought. (You can try the exercise at nytimes.com/tierneylab.) It may seem odd that we need these exercises — why would natural selection leave us with such unproductive fetishes? — perhaps because evolution is good at getting us to avoid death, desperation and celibacy, but not that good at getting us to feel happy...our desire to impress strangers may be a quirky evolutionary byproduct of a smaller social world...“We evolved as social primates who hardly ever encountered strangers in prehistory,” Miller says. “So we instinctively treat all strangers as if they’re potential mates or friends or enemies. But your happiness and survival today don’t depend on your relationships with strangers. It doesn’t matter whether you get a nanosecond of deference from a shopkeeper or a stranger in an airport.”

Bad drives reactions, Good propels behaviors

From Wang et al., slightly edited:
Research across disciplines suggests that bad is stronger than good and that individuals punish deception more than they reward honesty. However, methodological issues in previous research limit the latter conclusion. Three experiments resolved these issues and consistently found the opposite pattern: In the first experiment individuals rewarded honesty more frequently and intensely than they punished deception. The second experiment extended these counter-intuitive findings by revealing a divergence between evaluation and behavior: Evaluative reactions to deception were stronger than those to honesty, but behavioral intentions in response to honesty were stronger than those in response to deception. In addition, individuals wanted to avoid deceivers more than they wanted to approach honest actors. The third experiment found that punishment, but not reward, frequencies were sensitive to costs. Moderated-mediation tests revealed the role of different psychological mechanisms: Negative affect drove punishments, whereas perceived trustworthiness drove rewards. Overall, bad appears to be stronger than good in influencing psychological reactions, but good seems to be stronger than bad in influencing behavior.

Wednesday, May 20, 2009

Why I am loyal to Wisconsin...

From the UN Human Development Index for U.S. states and MapScroll:

Hubris syndrome: An acquired personality disorder?

Sigh....a nice clinical description of our recently departed president...Owen and Davidson offer a study of US presidents and UK prime ministers over the past 100 years. Here are a few clips:
We believe that extreme hubristic behaviour is a syndrome, constituting a cluster of features (‘symptoms’) evoked by a specific trigger (power), and usually remitting when power fades. ‘Hubris syndrome’ is seen as an acquired condition, and therefore different from most personality disorders which are traditionally seen as persistent throughout adulthood. The key concept is that hubris syndrome is a disorder of the possession of power, particularly power which has been associated with overwhelming success, held for a period of years and with minimal constraint on the leader.

The ability to make swift decisions, sometimes based on little evidence, is of particular importance—arguably necessary—in a leader. Similarly, a thin-skinned person will not be able to stand the process of public scrutiny, attacks by opponents and back-stabbings from within, without some form of self-exultation and grand belief about their own mission and importance. Powerful leaders are a highly selected sample and many criteria of any syndrome based on hubris are those behaviours by which they are probably selected—they make up the pores of the filter through which such individuals must pass to achieve high office.
Owen and Davidson define hubris syndrome:
...as a pattern of behaviour in a person who: (i) sees the world as a place for self-glorification through the use of power; (ii) has a tendency to take action primarily to enhance personal image; (iii) shows disproportionate concern for image and presentation; (iv) exhibits messianic zeal and exaltation in speech; (v) conflates self with nation or organization; (vi) uses the royal ‘we’ in conversation; (vii) shows excessive self-confidence; (viii) manifestly has contempt for others; (ix) shows accountability only to a higher court (history or God); (x) displays unshakeable belief that they will be vindicated in that court; (xi) loses contact with reality; (xii) resorts to restlessness, recklessness and impulsive actions; (xiii) allows moral rectitude to obviate consideration of practicality, cost or outcome; and (xiv) displays incompetence with disregard for nuts and bolts of policy making.

Meditation alters autonomic and central nervous system interaction.

I pass on this new abstract from Tang et al, which makes observations that correlate with my own subjective experiences of meditation :
Five days of integrative body–mind training (IBMT) improves attention and self-regulation in comparison with the same amount of relaxation training. This paper explores the underlying mechanisms of this finding. We measured the physiological and brain changes at rest before, during, and after 5 days of IBMT and relaxation training. During and after training, the IBMT group showed significantly better physiological reactions in heart rate, respiratory amplitude and rate, and skin conductance response (SCR) than the relaxation control. Differences in heart rate variability (HRV) and EEG power suggested greater involvement of the autonomic nervous system (ANS) in the IBMT group during and after training. Imaging data demonstrated stronger subgenual and adjacent ventral anterior cingulate cortex (ACC) activity in the IBMT group. Frontal midline ACC theta was correlated with high-frequency HRV, suggesting control by the ACC over parasympathetic activity. These results indicate that after 5 days of training, the IBMT group shows better regulation of the ANS by a ventral midfrontal brain system than does the relaxation group. This changed state probably reflects training in the coordination of body and mind given in the IBMT but not in the control group. These results could be useful in the design of further specific interventions.

Tuesday, May 19, 2009

Arts and the Brain

From the Dana Foundation, accounts of several neuro-education conferences on linking the Arts and intelligence. , musical training changing brain networks, etc.

Enhanced attention skills in video game players.

The July issue of Neuropsychologia offers yet another article, by Dye et al., on how video games enhance attentional resources:
Previous research suggests that action video game play improves attentional resources, allowing gamers to better allocate their attention across both space and time. In order to further characterize the plastic changes resulting from playing these video games, we administered the Attentional Network Test (ANT) to action game players and non-playing controls aged between 7 and 22 years. By employing a mixture of cues and flankers, the ANT provides measures of how well attention is allocated to targets as a function of alerting and orienting cues, and to what extent observers are able to filter out the influence of task irrelevant information flanking those targets. The data suggest that action video game players of all ages have enhanced attentional skills that allow them to make faster correct responses to targets, and leaves additional processing resources that spill over to process distractors flanking the targets.

Genetic bias of our amygdala-mediated economic decisions

Yet another nugget from the group associated with Ray Dolan at University College, London.
Genetic variation at the serotonin transporter-linked polymorphic region (5-HTTLPR) is associated with altered amygdala reactivity and lack of prefrontal regulatory control. Similar regions mediate decision-making biases driven by contextual cues and ambiguity, for example the "framing effect." We hypothesized that individuals hemozygous for the short (s) allele at the 5-HTTLPR would be more susceptible to framing. Participants, selected as homozygous for either the long (la) or s allele, performed a decision-making task where they made choices between receiving an amount of money for certain and taking a gamble. A strong bias was evident toward choosing the certain option when the option was phrased in terms of gains and toward gambling when the decision was phrased in terms of losses (the frame effect). Critically, this bias was significantly greater in the ss group compared with the lala group. In simultaneously acquired functional magnetic resonance imaging data, the ss group showed greater amygdala during choices made in accord, compared with those made counter to the frame, an effect not seen in the lala group. These differences were also mirrored by differences in anterior cingulate–amygdala coupling between the genotype groups during decision making. Specifically, lala participants showed increased coupling during choices made counter to, relative to those made in accord with, the frame, with no such effect evident in ss participants. These data suggest that genetically mediated differences in prefrontal–amygdala interactions underpin interindividual differences in economic decision making.

Monday, May 18, 2009

A new brain correlate of intention.

We have another installment in the story of how our conscious intention to move involves brain processes parallel to those that actually command the movements. It has been known for some time that stimulation of the presupplementary motor area in clinical exploration before brain surgery can produce an 'urge to move.' Desmurget et al. now find that stimulating areas in the inferior posterior parietal cortex (usually presumed to be involved in sensory motor coordination, not volition) can cause an urge to move specific body parts. When stimulation intensity was increased in parietal areas, participants believed they had really performed these movements, although no electromyographic activity was detected. Stimulation of the premotor region triggered overt mouth and contralateral limb movements. Yet, patients firmly denied that they had moved. Conscious intention and motor awareness thus arise from increased parietal activity before movement execution. Here is a figure from the review of this work by Haggard.


Voluntary action. (Top) The premotor cortex prepares commands for voluntary actions triggered by external stimuli, whereas the presupplementary motor area prepares commands for internally generated "intentional" actions, which are then executed by the primary motor cortex. Signals containing copies of prepared motor commands are also sent to the parietal cortex, where they are used to predict sensory consequences of movement. (Bottom) The preparation of motor commands for voluntary movement by the presupplementary motor area causes a sense of urge. The inferior part of the posterior parietal cortex generates sensory representations of the predicted consequences of the movement.

Evolutionary change driven by sufficiency, not survival

Polymath Adam Gopnik writes a nice piece in the May 11 issue of The New Yorker titled "The Fifth Blade." The title refers to the appearance (evolution) of razors with increasingly (functionally irrelevant) numbers of blades since the Wilkinson Sword company started mass-producing stainless-steel blades in 1961. This is consonant with a new suggested principle of biological evolution, quite at variance with the classical view that innovation is borne out of a struggle for survival amidst limited resources - that in dull periods of plenty, stasis was supposed to rule.
The new idea is almost the opposite. Terrence Deacon, for instance, a professor of biological anthropology and linguistics at Berkeley, has argued that animals' appearance alters and their behavior changes - birds brighten and their songs grow elaborate - not in conditions of scarcity, where bird fights bird for every seed, but in landscapes of plentitude...once "selection pressure" lifts - once it doesn't matter so much if every claw kills, if every molar crunches - then the animal can do its own thing and find its own pleasures. This pattern makes for what Deacon calls "relaxed selection, like relaxed-fit jeans.

Relaxed evolution favors the Ronald Firbanks over the Cotton Mathers, the playful dandy over the sober saver. Relaxed selection explains creativity in language and literature: once we no longer have to pressure our bodies to chew and hunt, the big heads behind them, having nothing to do, start doing what they please. It isn't the struggle for existence but the serenity of entertainment that explains our lives. The brain starts thinking as the jaw relaxes. We human beings are all three-blade razors, Gillete Mach3 Turbos and Shick Xtreme3s, with needless cutting surfaces and useless batteries, buzzing away, wasting energy and look sexy, forged in plenty and thriving in abundance.

Friday, May 15, 2009

How the brain talks to itself - errors in emotional prediction

Gilbert and Wilson offer an engaging essay in the Philisophical Transactions of the Royal Society B (PDF here) titled: "Why the brain talks to itself: sources of error in emotional prediction." In trying to plan futures that involve more pleasure than pain, we perform mental simulations (previews) of future events, which produce affective reactions (premotions), which are then used as a basis for forecasts (predictions) about the future event’s emotional consequences. Their review summarizes several main sources of systematic errors of these predictions.

Previews have several problems of dissimilar content:
1. They provide a poor basis for prediction because they tend to be based on memories that are not representative of the future events that those previews were meant to simulate.
2. They tend to omit features that are incidental to the event but that nonetheless may have a significant impact on our emotional reactions to it.
3. They tend to emphasize the early occurring moments of the event in which emotions are likely to be the most intense.
4. They include comparisons that views do not. (Imaginary chips are readily compared to imaginary sardines, but real chips are not.)
Previews also have problems of dissimilar context:
...accurate predictions also require that the context in which previewing occurs be similar to the context in which viewing occurs, and as it turns out, this is not always the case either. Why do contexts matter? Premotions are not just reactions to previews; they are reactions to previews and to the context in which those previews are generated. That is why we feel happier when we preview chocolate cake while we are lying on a comfortable couch than on a bed of nails, or when we are hungry rather than sated.

Brain activation in cocaine addicts caused by drug words

From Goldstein et al. :
When exposed to drug conditioned cues (stimuli associated with the drug), addicted individuals experience an intense desire for the drug, which is associated with increased dopamine cell firing. We hypothesized that drug-related words can trigger activation in the mesencephalon, where dopaminergic cells are located. During functional magnetic resonance imaging (fMRI), 15 individuals with cocaine use disorders and 15 demographically matched healthy control subjects pressed buttons for color of drug-related versus neutral words. Results showed that the drug words, but not neutral words, activated the mesencephalon in the cocaine users only. Further, in the cocaine users only, these increased drug-related mesencephalic responses were associated with enhanced verbal fluency specifically for drug words. Our results for the first time demonstrate fMRI response to drug words in cocaine-addicted individuals in mesencephalic regions as possibly associated with dopaminergic mechanisms and with conditioning to language (in this case drug words). The correlation between the brief verbal fluency test, which can be easily administered (crucial for clinical studies), and fMRI cue reactivity could be used as a biomarker of neurobiological changes in addiction.

Thursday, May 14, 2009

Stepping backwards enhances cognitive control.

From Koch et al., some interesting work on the role of body locomotion in the recruitment of control processes.:
In the most fundamental and literal sense, approach refers to decreasing, and avoidance to increasing, the physical distance between the self and the outside world. In our view, body locomotion most purely taps into this fundamental nature of approach and avoidance. In everyday life, individuals typically approach desired stimuli by stepping forward and avoid aversive stimuli by stepping backward

...The idea that body locomotion may trigger approach and avoidance orientations has, so far, not been tested...we expected that stepping backward would increase the recruitment of cognitive control relative to stepping forward. To test this prediction, we gauged cognitive functioning by means of a Stroop task immediately after a participant stepped in one direction. The Stroop task requires naming the color in which stimulus words are printed while ignoring their semantic meaning, which is actually processed more automatically than the color. Cognitive control is required to override the tendency to respond to the semantic meaning and instead respond to the color.

...our study showed that stepping backward significantly enhanced cognitive performance compared to stepping forward or sideways. Considering the effect size, backward locomotion appears to be a very powerful trigger to mobilize cognitive resources. Thus, whenever you encounter a difficult situation, stepping backward may boost your capability to deal with it effectively.

Putting Off Growing Old

I pass on this item by Sherman Sutter from the editor's choice section of Science Magazine:
In a classic 1957 paper on the evolution of senescence, Williams argued that when extrinsic mortality (death due to predation, infectious disease, or accident) is high, natural selection favors investment in early reproduction. When it is low, the increased return from allocating resources to maintain and repair the soma should lead to longer life spans. In the absence of precise information on causes of death, researchers have used hazard models to partition mortality into age-independent (interpreted as extrinsic) and age-dependent components.

Taking this approach, Gurven and Fenelon analyze mortality data from 13 remote, small-scale societies and in historical cohorts from Sweden and England over the past 250 years. They explore two statistical models (Weibull and Gompertz-Makeham) of adult mortality patterns and consider three measures of actuarial aging (mortality rate doubling time, Ricklefs's {omega}, and slope of the mortality function between ages 60 and 70). The variation in results across these two estimation procedures and three measures complicates the interpretation of the data. Nonetheless, some patterns are robust: The subsistence groups and the early Swedish cohorts exhibit similar actuarial aging, but more recent European cohorts show progressively slower aging. In the longitudinal samples, slower aging and reduced extrinsic mortality are linked. Women have lower rates of senescence than men, a difference that has increased over time. These "modest but nontrivial" changes support Williams's claims, and the authors discuss individual-level mechanisms that could underlie them.

Wednesday, May 13, 2009

Experience as what we agree to attend to...

I have decided to paste in just a fragment of writing from a parallel private journal that I keep. It has some of my private jargon, apologies if it is not intelligible to you. It is a random walk...
...that wants to try to crystallize something from last Wednesday’s post on attention together with a reading (still going on) of Metzinger’s recent book “The Ego Tunnel.” Metzinger’s compelling analysis, along with others, shows our introspective selves to be fictions even if they are imaged to fit in a metacognitive hierarchy, such as a watcher (closer to a Damasio-style homeostatic pre-emotional core) that is sensed as observer of its products (being an angry/happy/kind/compassionate/whatever person.) All are actually logically equivalent (watch-ing, be-ing, angry-ing, desire-ing, compassion-ing). Even while being in principle illusory, many of these self models can be shown to correlate with distinctive pattern of brain activity, can be altered by brain lesions. The experiential and behavioral issue is which of these members of an imaginary governing board is being held within the limited attentional resources of the frontal lobes. (William James: “My experience is what I agree to attend to.”). Training regimes that settle this issue by putting in place new habits for what is held in attention (compassion meditation, piano or other athletic practice, etc.) can be transformative. Physical changes in brain areas serving these functions can be documented.

Prelinguistic infants, but not chimps, signal absent entities

Interesting work from Tomasello's group showing that nonlinguistic skills for displaced reference precede and underlie similar linguistic reference:
One of the defining features of human language is displacement, the ability to make reference to absent entities. Here we show that prelinguistic, 12-month-old infants already can use a nonverbal pointing gesture to make reference to absent entities. We also show that chimpanzees—who can point for things they want humans to give them—do not point to refer to absent entities in the same way. These results demonstrate that the ability to communicate about absent but mutually known entities depends not on language, but rather on deeper social-cognitive skills that make acts of linguistic reference possible in the first place. These nonlinguistic skills for displaced reference emerged apparently only after humans' divergence from great apes some 6 million years ago.
In carrying out the experiments the authors:
...confronted 12-month-old prelinguistic human infants and adult chimpanzees with two new situations in which they wanted something they could not see. In both situations, participants first repeatedly saw a human adult place several desired objects of the same kind on top of one platform, while also placing undesired objects of another kind on another, similar platform. Then, for the test, the desired objects were removed. In the occluded-referent condition, participants then saw the adult take another object of the desired kind and place it under its platform, out of sight. In this case, even though participants could not see the desired object, they knew it was there under the platform, and so they could potentially request it by pointing to its location. In the absent-referent condition, in contrast, after the adult removed the desired objects from the platform, she did not add any more, so that the usual location of the desired kind of objects was empty. In this case, if participants pointed to the now-empty platform, it would mean that they expected the adult would be able to infer that what they wanted was one of the missing kind of objects, that is, one of the kind both the adult and the participants knew was usually on that platform.