Fixation Patterns During Recognition of Personally Familiar and Unfamiliar Faces

Previous studies recording eye gaze during face perception have rendered somewhat inconclusive findings with respect to fixation differences between familiar and unfamiliar faces. This can be attributed to a number of factors that differ across studies: the type and extent of familiarity with the faces presented, the definition of areas of interest subject to analyses, as well as a lack of consideration for the time course of scan patterns. Here we sought to address these issues by recording fixations in a recognition task with personally familiar and unfamiliar faces. After a first common fixation on a central superior location of the face in between features, suggesting initial holistic encoding, and a subsequent left eye bias, local features were focused and explored more for familiar than unfamiliar faces. Although the number of fixations did not differ for un-/familiar faces, the locations of fixations began to differ before familiarity decisions were provided. This suggests that in the context of familiarity decisions without time constraints, differences in processing familiar and unfamiliar faces arise relatively early – immediately upon initiation of the first fixation to identity-specific information – and that the local features of familiar faces are processed more than those of unfamiliar faces

Face inversion and acquired prosopagnosia reduce the size of the perceptual field of view

Using a gaze-contingent morphing approach, we asked human observers to choose one of two faces that best matched the identity of a target face: one face corresponded to the reference face’s fixated part only (e.g., one eye), the other corresponded to the unfixated area of the reference face. The face corresponding to the fixated part was selected significantly more frequently in the inverted than in the upright orientation. This observation provides evidence that face inversion reduces an observer’s perceptual field of view, even when both upright and inverted faces are displayed at full view and there is no performance difference between these conditions. It rules out an account of the drop of performance for inverted faces – one of the most robust effects in experimental psychology – in terms of a mere difference in local processing efficiency. A brain-damaged patient with pure prosopagnosia, viewing only upright faces, systematically selected the face corresponding to the fixated part, as if her perceptual field was reduced relative to normal observers. Altogether, these observations indicate that the absence of visual knowledge reduces the perceptual field of view, supporting an indirect view of visual perception

Recent advances for monitoring groundwater and pollutant fluxes using single-well applied tracer techniques

In many different hydrogeological investigations, quantifying groundwater fluxes is essential but often challenging due to the variability of hydraulic conditions in space and time. Traditional approaches used to estimate groundwater fluxes are based on hydraulic conductivity obtained from field pumping or slug tests that provide only order-of-magnitude estimates and hydraulic gradients that can also vary, especially in areas of active groundwater discharge or pumping. The Finite Volume Point Dilution Method (FVPDM) is a recently developed applied tracer technology able to measure accurately groundwater fluxes and to monitor continuously their changes with time. We report 10 years of application of the FVPDM in contrasted hydrogeological contexts, from porous alluvial to fractured-rock aquifers, including strong interactions with surface water and contrasting groundwater flow dynamics. The obtained results prove that the FVPDM is able to measure a wide range of groundwater fluxes from a few centimetres per day to hundreds of metres per day. These results also emphases the variability in groundwater fluxes, (1) with time in aquifers influenced by variable hydraulic conditions such as tidal effects and (2) in space where orders of magnitude difference in groundwater fluxes are observed between nearby monitoring wells at a given site. Preliminary results of continuing work have also shown the potential for the FVPDM approach to be coupled with contaminant specific sensors and with passive sampling technologies to quantify contaminant mass fluxes in the subsurface. Recent developments have also investigated the ability to assess groundwater flow directions at the well scale

Ping­pong skull fracture in the newborn: to treat or not to treat ?

Case Description: A 2.870g female infant was born at 38 weeks via vaginal delivery in occipito-posterior position. Because of a prolonged second stage of labour and recurrent late decelerations indicating foetal distress, the delivery was vacuum-assisted with a cup placed on the right side of the forehead. At birth, a depression of the left parietal skull was noted, measuring approximately 5 mm in depth and 40 mm in diameter. The depression had a bony base and no accompanying oedema or hematoma. Neurologic and physical examination revealed no other abnormalities. A thorough review of the perinatal history could not identify a causal trauma. Radiography of the maternal pelvis showed no abnormalities. An X-ray of the skull was performed to evaluate the depression, indicating a ping-pong fracture. Computed tomography (CT) scan additionally demonstrated a small zone of contusion below the depression. Surgical elevation was opted because of this underlying contusion. A follow-up CT-scan was performed the day after surgery, which showed complete resolution of the depression and a small subarachnoid haemorrhage. The child was discharged home on day 7 with a normal neurological examination. Discussion: A ping-pong fracture is a type of fracture seen only in neonates and young infants. It consists of a depression of the skull without cortical break. These depressed skull fractures can either be congenital or acquired. Congenital depressions of the neonatal skull unrelated to trauma are rare and often puzzling in origin. They are referred to as “faulty fetal packing”, since they are caused by external pressure in utero, e.g. by a bony prominence of the maternal pelvis or spine. Non-traumatic, congenital depression fractures are the result of moulding of the soft foetal skull during its intra-uterine stay. Intra-cranial abnormalities are therefore rare. Acquired depressed skull fractures are more common and are usually caused by birth trauma due to obstetric manoeuvres or instrumental delivery. The acquired type of depressed fracture carries a higher risk of intra-cranial lesions, because of the sudden and important force applied to the skull. Management of ping-pong fractures in newborns is based on careful history taking and thorough clinical examination. A difficult delivery, e.g. with need for instrumentation, is more likely to cause traumatic ping-pong fractures and must always alert the clinician with respect to possible intra-cranial damage. Surgical lifting of the bone must be considered and was therefore applied in this case. A trouble-free birth without perinatal history for trauma and a newborn without neurological symptoms, is more likely a case of “faulty fetal packing”. This can be treated conservatively, as full and spontaneous resolution within the first few months of life has been described. Surgical correction is necessary when spontaneous resolution has not occurred by 6 months of age or when neurological symptoms appear

Face inversion impairs holistic perception : evidence from gaze-contingent stimulation

Human observers are experts at face recognition, yet a simple 180 degrees rotation of a face photograph decreases recognition performance substantially. A full understanding of this phenomenon-which is believed to be important for clarifying the nature of our expertise in face recognition-is still waiting. According to a long-standing and influential hypothesis, an inverted face cannot be perceived as holistically as an upright face and has to be analyzed local feature by local feature. Here, we tested this holistic perception hypothesis of the face inversion effect by means of a gaze-contingent stimulus presentation. When observers' perception was restricted to one fixated feature at a time by a gaze-contingent window, performance in an individual face matching task was almost unaffected by inversion. However, when a mask covered the fixated feature, preventing the use of local information at high resolution, the decrement of performance with inversion was even larger than in a normal-full view-condition. These observations provide evidence that the face inversion effect is caused by an inability to perceive the individual face as a whole rather than as a collection of specific features and thus support the view that observers' expertise at upright face recognition is due to the ability to perceive an individual face holistically

Economic Implications of a Protein Transition: Evidence From Walloon Beef and Dairy Farms

In Europe, cattle production is confronted with major challenges across all dimensions of sustainability, urging the need to promote environmentally friendly but also economically viable livestock systems. In addition, animal protein consumption greatly exceeds the dietary guidelines in most European countries. The protein transition, defined as the rebalancing between animal and alternative proteins in diets, is presented as a solution to mitigate the harmful effects of cattle production on the environment, but also as an opportunity to induce healthier diets. Yet, the implications of such a transition on current livestock farmers are still unclear. In this article, we investigate different factors associated with a protein transition (e.g., reduction of herd size, increased concentrate autonomy and increased share of pastures) and assess their implications for the economic performance of dairy and beef farmers in Wallonia, Belgium. In the dairy sector, we find that a reduction in herd size, a higher share of pastures and an increased concentrate autonomy are correlated with lower operating costs, resulting in higher margins. Therefore, a switch to more extensive grazing systems that rely on on-farm fodder production can entail economic benefits for farmers. In the beef sector, on the other hand, farm characteristics are uncorrelated with most economic indicators, but highly associated with subsidies. This suggests that changes in this sector will rather be induced by policy choices than by economic parameters

Impairment of holistic face perception following right occipito-temporal damage in prosopagnosia : converging evidence from gaze-contingency

Gaze-contingency is a method traditionally used to investigate the perceptual span in reading by selectively revealing/masking a portion of the visual field in real time. Introducing this approach in face perception research showed that the performance pattern of a brain-damaged patient with acquired prosopagnosia (PS) in a face matching task was reversed, as compared to normal observers: the patient showed almost no further decrease of performance when only one facial part (eye, mouth, nose, etc.) was available at a time (foveal window condition, forcing part-based analysis), but a very large impairment when the fixated part was selectively masked (mask condition, promoting holistic perception) (Van Belle, De Graef, Verfaillie, Busigny, & Rossion, 2010a; Van Belle, De Graef, Verfaillie, Rossion, & Lefèvre, 2010b). Here we tested the same manipulation in a recently reported case of pure prosopagnosia (GG) with unilateral right hemisphere damage (Busigny, Joubert, Felician, Ceccaldi, & Rossion, 2010). Contrary to normal observers, GG was also significantly more impaired with a mask than with a window, demonstrating impairment with holistic face perception. Together with our previous study, these observations support a generalized account of acquired prosopagnosia as a critical impairment of holistic (individual) face perception, implying that this function is a key element of normal human face recognition. Furthermore, the similar behavioral pattern of the two patients despite different lesion localizations supports a distributed network view of the neural face processing structures, suggesting that the key function of human face processing, namely holistic perception of individual faces, requires the activity of several brain areas of the right hemisphere and their mutual connectivity