A bottom–up model of spatial attention predicts human error patterns in rapid scene recognition

Humans demonstrate a peculiar ability to detect complex targets in rapidly presented natural scenes. Recent studies suggest that (nearly) no focal attention is required for overall performance in such tasks. Little is known, however, of how detection performance varies from trial to trial and which stages in the processing hierarchy limit performance: bottom–up visual processing (attentional selection and/or recognition) or top–down factors (e.g., decision-making, memory, or alertness fluctuations)? To investigate the relative contribution of these factors, eight human observers performed an animal detection task in natural scenes presented at 20 Hz. Trial-by-trial performance was highly consistent across observers, far exceeding the prediction of independent errors. This consistency demonstrates that performance is not primarily limited by idiosyncratic factors but by visual processing. Two statistical stimulus properties, contrast variation in the target image and the information-theoretical measure of “surprise” in adjacent images, predict performance on a trial-by-trial basis. These measures are tightly related to spatial attention, demonstrating that spatial attention and rapid target detection share common mechanisms. To isolate the causal contribution of the surprise measure, eight additional observers performed the animal detection task in sequences that were reordered versions of those all subjects had correctly recognized in the first experiment. Reordering increased surprise before and/or after the target while keeping the target and distractors themselves unchanged. Surprise enhancement impaired target detection in all observers. Consequently, and contrary to several previously published findings, our results demonstrate that attentional limitations, rather than target recognition alone, affect the detection of targets in rapidly presented visual sequences

tert-Butyl N-benzyl-N-[4-(4-fluoro­benzoyl­meth­yl)-2-pyrid­yl]carbamate

In the crystal structure of the title compound, C25H25FN2O3, the pyridine ring makes dihedral angles of 75.1 (3), 39.4 (3) and 74.6 (3)° with the phenyl ring, the carbamate plane and the 4-fluoro­phenyl ring, respectively. The phenyl ring makes dihedral angles of 77.2 (3) and 23.6 (3)° with the carbamate plane and the 4-fluoro­phenyl ring, respectively. The 4-fluoro­phenyl ring is perpendicular to the carbamate plane, the dihedral angle between them being 89.5 (3)°

N-{4-[3-(4-Fluoro­phen­yl)pyrido[2,3-b]pyrazin-2-yl]-2-pyrid­yl}isopropyl­amine

In the crystal structure of the title compound, C21H18FN5, the pyridopyrazine ring system forms dihedral angles of 33.27 (7) and 48.69 (9)° with the 4-fluoro­phenyl and pyridine ring, respectively. The dihedral angle of the 4-fluoro­phenyl and pyridine rings is 57.45 (8)°. The crystal packing is characterized by an inter­molecular N—H⋯N hydrogen bond

2-(4-Fluoro­phen­yl)-3-(4-pyrid­yl)pyrido[2,3-b]pyrazine

In the crystal structure of the title compound, C18H11FN4, the pyridopyrazine system makes dihedral angles of 45.51 (7) and 44.75 (7)° with the attached 4-fluoro­phenyl ring and the pyridine ring, respectively. The 4-fluoro­phenyl ring makes a dihedral angle of 54.54 (8)° with the pyridine ring. The pyridine ring part of the pyridopyrazine ring and the pyrazine ring of two c-glide-plane-related mol­ecules form π–π inter­actions. The angle between the planes is 2.09 (7)° and the distance between the centroids is 3.557 (1)Å

tert-Butyl N-benzyl-N-(4-methyl-2-pyrid­yl)carbamate

In the crystal structure of the title compound, C18H22N2O2, the pyridine ring makes dihedral angles of 83.71 (6) and 9.2 (1)° with the phenyl ring and the carbamate plane, respectively. The phenyl ring and the carbamate plane are nearly perpendicular to one another, with a dihedral angle of 87.17 (7)°

4-[5-(4-Fluoro­phen­yl)-1H-imidazol-4-yl]pyridine

In the title compound, C14H10FN3, the imidazole ring makes dihedral angles of 28.2 (1) and 36.60 (9)° with the pyridine ring and the 4-fluoro­phenyl ring, respectively. The pyridine ring forms a dihedral angle of 44.68 (9)° with the 4-fluoro­phenyl ring. Inter­molecular N—H⋯N hydrogen bonds are observed in the crystal structure

Ethyl 5-amino-3-(pyridin-4-yl)-1-(2,4,6-tri­chloro­phen­yl)-1H-pyrazole-4-carb­oxyl­ate dimethyl sulfoxide hemisolvate

The asymmetric unit of the title compound, C17H13Cl3N4O2·0.5C2H6OS, contains two almost identical mol­ecules and one dimethyl sulfoxide (DMSO-d 6) solvent mol­ecule. The pyrazole ring forms dihedral angles of 54.6 (4) and 80.0 (4)° in one mol­ecule, and dihedral angles of 54.2 (4) and 81.2 (4)° in the other mol­ecule, with the directly attached pyridine and trichloro­phenyl rings, respectively. The dihedral angles of the pyridine and trichloro­phenyl rings are 51.2 (4) and 52.0 (4)°, respectively. The crystal packing is characterized by intra- and inter­molecular hydrogen bonds. The crystal is a nonmerohedral twin with a contribution of 0.488 (1) for the minor twin component. The terminal ethyl group of one mol­ecule and the S atom of DMSO are disordered over two sites

4-(4-Fluoro­phen­yl)-1-(4-nitro­phen­yl)-3-(pyridin-4-yl)-1H-pyrazol-5-amine

In the crystal structure of the title compound, C20H14FN5O2, the pyrazole ring forms dihedral angles of 59.3 (2), 25.6 (2) and 46.0 (2)° with the directly attached 4-fluoro­phenyl, pyridine and nitro­phenyl rings, respectively. The crystal packing is characterized by inter­molecular N—H⋯N and N—H⋯O hydrogen bonds

tert-Butyl N-(4-methyl-2-pyrid­yl)­carbamate

The crystal structure of the title compound, C11H16N2O2, contains two crystallographically independent mol­ecules forming dimers by pairs of inter­molecular N—H⋯N hydrogen bonds. The two mol­ecules are related by a pseudo-twofold axis. The dihedral angle between the pyridine ring and the carbamate plane differs in the two mol­ecules [12.1 (3) and 3.5 (3)°]

Comparison of four simple wave resistance formulas

Thesis (Ocean E)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1980.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERINGIncludes bibliographical references.by Pierre Francois Koch.Ocean